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标题: MyBatis 查询数据库 [打印本页]

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作者: 张国伟    时间: 2022-6-25 17:25
标题: MyBatis 查询数据库
文章目录

• 1. 什么是MyBatis
  
• 2. 配置 MyBatis 的开发环境
  
• 
  
  
  
  • 2.1 准备工作, 创建数据库和表
    
  • 2.2 添加 MyBatis 依赖
    
  • 2.3 配置连接字符串和 MyBatis
    
  • 
    
    
    
    • 2.3.1 配置数据库连接信息
      
    • 2.3.2 配置 MyBatis 中的 XML 路径
      
       
    
  • 2.4 添加代码
    
  • 
    
    
    
    • 2.4.1 添加实体类
      
    • 2.4.2 添加 mapper 接口
      
    • 2.4.3 添加 UserMapper.xml
      
    • 2.4.4 添加 Service
      
    • 2.4.5 添加 Controller
      
    • 2.4.6 测试代码
      
       
    
  • 2.5 注意事项
    
    
  
• 3. MyBatis 的增删改查操作.
  
• 
  
  
  
  • 3.1 增加操作
    
  • 3.2 查找操作
    
  • 3.3 修改操作
    
  • 3.4 删除操作
    
    
  
• 4. MyBatis 的进阶操作
  
• 
  
  
  
  • 4.1 返回自增id
    
  • 
    
    
    
    • 4.1.1 添加 controller 实现代码
      
    • 4.1.2 添加 service 实现代码
      
    • 4.1.3 添加 mapper 接口
      
    • 4.1.4 添加 xml
      
    • 4.1.5 测试代码
      
       
    
  • 4.2 一对一的表映射
    
  • 
    
    
    
    • 4.2.1 xml中具体的实现
      
    • 4.2.2 Blog 实体类
      
    • 4.2.3 添加 controll
      
    • 4.2.4 添加 service
      
    • 4.2.5 添加 mapper
      
    • 4.2.6 测试运行
      
       
    
  • 4.3 一对多的表映射
    
  • 
    
    
    
    • 4.3.1 xml中具体的实现
      
    • 4.3.2 添加 controller
      
    • 4.3.3 添加 service
      
    • 4.3.4 添加 mapper接口
      
    • 4.3.5 测试运行
      
      
    
    
  
• 5. MyBatis 的一些注意事项
  
• 
  
  
  
  • 5.1 参数占位符 #{} 和 ${}
    
  • 
    
    
    
    • 5.1.1 ${} 的优点
      
       
    
  • 5.2 SQL 注入问题
    
  • 5.3 like 查询
    
  • 5.4 实体类中的字段和mysql中的字段不匹配
    
  • 5.5 想要在控制台查看 mybatis 的日志
    
  • 5.6 编写 MyBatis 更方便的插件
    
    
  
• 6. 动态 SQL
  
• 
  
  
  
  • 6.1 if 标签
    
  • 6.2 trim 标签
    
  • 6.3 where 标签
    
  • 6.4 set 标签
    
  • 6.5 foreach 标签
    
  
  

1. 什么是MyBatis

   MyBatis 是一款优秀的持久层框架，它支持自定义 SQL、存储过程以及高级映射。
 
MyBatis 免除了几乎所有的 JDBC 代码以及设置参数和获取结果集的工作。
 
MyBatis 可以通过简单的 XML 或 注解 来配置和映射原始类型、接口和 Java POJO（Plain Old Java Objects，普通老式 Java 对象）为数据库中的记录。
  用一句简单的话来概述: MyBatis 是更简单完成程序和数据库交互的工具或 MyBatis 是更简单的操作和读取数据库工具
2. 配置 MyBatis 的开发环境


2.1 准备工作, 创建数据库和表

1. create database if not exists MyBlogSystem;
3. use MyBlogSystem;
5. drop table if exists blog;
7. -- 创建一个博客表
8. create table blog (
9. <?xml version="1.0" encoding="UTF-8"?>
10. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
11.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
12. <mapper namespace="com.example.demo.mapper.UserMapper">
13.    
14. </mapper>blogId int primary key auto_increment,
15. <?xml version="1.0" encoding="UTF-8"?>
16. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
17.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
18. <mapper namespace="com.example.demo.mapper.UserMapper">
19.    
20. </mapper>title varchar(1024),
21. <?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper>content mediumtext,
27. <?xml version="1.0" encoding="UTF-8"?>
28. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
29.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
30. <mapper namespace="com.example.demo.mapper.UserMapper">
31.    
32. </mapper>postTime datetime,
33. <?xml version="1.0" encoding="UTF-8"?>
34. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
35.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
36. <mapper namespace="com.example.demo.mapper.UserMapper">
37.    
38. </mapper>userId int
39. );
41. drop table if exists user;
43. -- 创建一个用户信息表
44. create table user (
45. <?xml version="1.0" encoding="UTF-8"?>
46. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
47.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
48. <mapper namespace="com.example.demo.mapper.UserMapper">
49.    
50. </mapper>userId int primary key auto_increment,
51. <?xml version="1.0" encoding="UTF-8"?>
52. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
53.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
54. <mapper namespace="com.example.demo.mapper.UserMapper">
55.    
56. </mapper>username varchar(128) unique,
57. <?xml version="1.0" encoding="UTF-8"?>
58. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
59.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
60. <mapper namespace="com.example.demo.mapper.UserMapper">
61.    
62. </mapper>password varchar(128)
63. );

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2.2 添加 MyBatis 依赖

1.                 <dependency>
2.                         <groupId>org.mybatis.spring.boot</groupId>
3.                         <artifactId>mybatis-spring-boot-starter</artifactId>
4.                         <version>2.2.2</version>
5.                 </dependency>
6.                 <dependency>
7.                         <groupId>mysql</groupId>
8.                         <artifactId>mysql-connector-java</artifactId>
9.                         <scope>runtime</scope>
10.                 </dependency>

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2.3 配置连接字符串和 MyBatis

2.3.1 配置数据库连接信息

1. spring.datasource.url=jdbc:mysql://localhost:3306/MyBlogSystem?characterEncoding=utf8&useSSL=true
2. spring.datasource.username=root
3. spring.datasource.password=root
4. spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

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2.3.2 配置 MyBatis 中的 XML 路径

配置 mybatis 的文件路径, 在 resources/mapper 创建所有表的xml文件

1. mybatis.mapper-locations=classpath:mapper/**Mapper.xml

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这里必须要一样

2.4 添加代码

2.4.1 添加实体类

添加用户的实体类

1. @Getter
2. @Setter
3. @ToString
4. public class User {
5. <?xml version="1.0" encoding="UTF-8"?>
6. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
7.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
8. <mapper namespace="com.example.demo.mapper.UserMapper">
9.    
10. </mapper>public int userId;
11. <?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>public String username;
17. <?xml version="1.0" encoding="UTF-8"?>
18. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
19.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
20. <mapper namespace="com.example.demo.mapper.UserMapper">
21.    
22. </mapper>public String password;
23. }

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2.4.2 添加 mapper 接口

1. @Mapper
2. public interface UserMapper {
3. <?xml version="1.0" encoding="UTF-8"?>
4. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
5.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
6. <mapper namespace="com.example.demo.mapper.UserMapper">
7.    
8. </mapper>List<User> getAll();
9. }

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2.4.3 添加 UserMapper.xml

固定的xml格式

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>

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这里的 UserMapper.xml

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>select * from user;<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>

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2.4.4 添加 Service

1. @Servicepublic class UserService {<?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>// 记得要注入<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper>@Resource<?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>private UserMapper userMapper;<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>public List getAll() {<?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper><?xml version="1.0" encoding="UTF-8"?>
27. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
28.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
29. <mapper namespace="com.example.demo.mapper.UserMapper">
30.    
31. </mapper>return userMapper.getAll();<?xml version="1.0" encoding="UTF-8"?>
32. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
33.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
34. <mapper namespace="com.example.demo.mapper.UserMapper">
35.    
36. </mapper>}}

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2.4.5 添加 Controller

1. // 这里的 @RestController 相当于 @Controller + @ResponseBody@RestController@RequestMapping("/user")public class UserController3 {<?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>@Autowired<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper>private UserService userService;<?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper><?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>@RequestMapping("/getall")<?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper>public List getAll() {<?xml version="1.0" encoding="UTF-8"?>
27. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
28.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
29. <mapper namespace="com.example.demo.mapper.UserMapper">
30.    
31. </mapper><?xml version="1.0" encoding="UTF-8"?>
32. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
33.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
34. <mapper namespace="com.example.demo.mapper.UserMapper">
35.    
36. </mapper>return userService.getAll();<?xml version="1.0" encoding="UTF-8"?>
37. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
38.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
39. <mapper namespace="com.example.demo.mapper.UserMapper">
40.    
41. </mapper>}}

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2.4.6 测试代码


2.5 注意事项

   

• 注意配置文件中的mapper配置和mapper文件夹的对应
  
• UserMapper.xml 这里需要一些路径对应, 以及id格式对应 , 这里的resultType是返回的类型.
  
  

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.demo.mapper.UserMapper">
   
</mapper>

• 按照业务规定流程写代码
  
  

  3. MyBatis 的增删改查操作.

3.1 增加操作

   步骤:
  

• 添加 实体类(这里有了就不需要添加了)
  
• 添加 controller
  
• 添加 service
  
• 添加 mapper 接口
  
• 添加 xml
  

  ① 添加 controller 实现代码

1. @RestController@RequestMapping("/user")public class UserController3 {<?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>@Autowired<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper>private UserService userService;<?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>@RequestMapping("/insert")<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>public Integer insert(User user) {<?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper><?xml version="1.0" encoding="UTF-8"?>
27. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
28.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
29. <mapper namespace="com.example.demo.mapper.UserMapper">
30.    
31. </mapper>return userService.insert(user);<?xml version="1.0" encoding="UTF-8"?>
32. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
33.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
34. <mapper namespace="com.example.demo.mapper.UserMapper">
35.    
36. </mapper>}}

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② 添加 service 实现代码

1. @Servicepublic class UserService {<?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>// 记得要注入<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper>@Resource<?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>private UserMapper userMapper;<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>public Integer insert(User user) {<?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper><?xml version="1.0" encoding="UTF-8"?>
27. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
28.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
29. <mapper namespace="com.example.demo.mapper.UserMapper">
30.    
31. </mapper>return userMapper.insert();<?xml version="1.0" encoding="UTF-8"?>
32. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
33.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
34. <mapper namespace="com.example.demo.mapper.UserMapper">
35.    
36. </mapper>}}

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③ 添加 mapper 接口

1. @Mapperpublic interface UserMapper {<?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>Integer insert();}

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④ 添加 xml

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>insert into user values (null, #{username},#{password});<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>

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⑤ 测试代码


3.2 查找操作

   步骤:
  

• 添加 实体类(这里有了就不需要添加了)
  
• 添加 controller
  
• 添加 service
  
• 添加 mapper 接口
  
• 添加 xml
  

  ① 添加 controller

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>@RequestMapping("/getall")<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper>public List getAll() {<?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper><?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>return userService.getAll();<?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper>}

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② 添加 service

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>@RequestMapping("/getall")<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper>public List getAll() {<?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper><?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>return userService.getAll();<?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper>}

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③ 添加 mapper 接口

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>public List getAll() {<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>return userMapper.getAll();<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>}

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④ 添加 xml

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>select * from user;<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>

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⑤ 测试代码

3.3 修改操作

   步骤:
  

• 添加 实体类(这里有了就不需要添加了)
  
• 添加 controller
  
• 添加 service
  
• 添加 mapper 接口
  
• 添加 xml
  

  ① 添加controller

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>@RequestMapping("/update")<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper>public Integer update(Integer userId, String password) {<?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper><?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>return userService.update(userId,password);<?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper>}

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② 添加 service

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>public Integer update(Integer userId, String password) {<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>return userMapper.update(userId,password);<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>}

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③ 添加 mapper 接口

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>Integer update(Integer userId, String password);

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④ 添加 xml

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>update user set password=#{password} where userId=#{userId}<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>

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⑤ 测试代码


3.4 删除操作

   步骤:
  

• 添加 实体类(这里有了就不需要添加了)
  
• 添加 controller
  
• 添加 service
  
• 添加 mapper 接口
  
• 添加 xml
  

  ① 添加 controller

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>@RequestMapping("/delete")<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper>public Integer delete(Integer userId) {<?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper><?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>return userService.delete(userId);<?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper>}

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② 3.4.2 添加 service

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>public Integer delete(Integer userId) {<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>return userMapper.delete(userId);<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>}

复制代码

③ 添加 mapper 接口

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>Integer delete(Integer userId);

复制代码

④ 添加 xml

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper>   delete from user where userId=#{userId}<?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>

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⑤ 测试代码


4. MyBatis 的进阶操作

4.1 返回自增id

这里用增加操作来进行演示
4.1.1 添加 controller 实现代码

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>@RequestMapping("/insert2")<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper>public Integer insert2(User user) {<?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper><?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>if (user == null || user.getUsername() == null<?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper><?xml version="1.0" encoding="UTF-8"?>
27. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
28.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
29. <mapper namespace="com.example.demo.mapper.UserMapper">
30.    
31. </mapper><?xml version="1.0" encoding="UTF-8"?>
32. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
33.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
34. <mapper namespace="com.example.demo.mapper.UserMapper">
35.    
36. </mapper><?xml version="1.0" encoding="UTF-8"?>
37. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
38.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
39. <mapper namespace="com.example.demo.mapper.UserMapper">
40.    
41. </mapper>|| user.getPassword() == null<?xml version="1.0" encoding="UTF-8"?>
42. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
43.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
44. <mapper namespace="com.example.demo.mapper.UserMapper">
45.    
46. </mapper><?xml version="1.0" encoding="UTF-8"?>
47. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
48.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
49. <mapper namespace="com.example.demo.mapper.UserMapper">
50.    
51. </mapper><?xml version="1.0" encoding="UTF-8"?>
52. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
53.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
54. <mapper namespace="com.example.demo.mapper.UserMapper">
55.    
56. </mapper><?xml version="1.0" encoding="UTF-8"?>
57. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
58.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
59. <mapper namespace="com.example.demo.mapper.UserMapper">
60.    
61. </mapper>|| user.getUsername().equals("")<?xml version="1.0" encoding="UTF-8"?>
62. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
63.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
64. <mapper namespace="com.example.demo.mapper.UserMapper">
65.    
66. </mapper><?xml version="1.0" encoding="UTF-8"?>
67. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
68.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
69. <mapper namespace="com.example.demo.mapper.UserMapper">
70.    
71. </mapper><?xml version="1.0" encoding="UTF-8"?>
72. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
73.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
74. <mapper namespace="com.example.demo.mapper.UserMapper">
75.    
76. </mapper><?xml version="1.0" encoding="UTF-8"?>
77. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
78.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
79. <mapper namespace="com.example.demo.mapper.UserMapper">
80.    
81. </mapper>|| user.getPassword().equals("")<?xml version="1.0" encoding="UTF-8"?>
82. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
83.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
84. <mapper namespace="com.example.demo.mapper.UserMapper">
85.    
86. </mapper><?xml version="1.0" encoding="UTF-8"?>
87. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
88.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
89. <mapper namespace="com.example.demo.mapper.UserMapper">
90.    
91. </mapper>) { // 非法参数<?xml version="1.0" encoding="UTF-8"?>
92. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
93.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
94. <mapper namespace="com.example.demo.mapper.UserMapper">
95.    
96. </mapper><?xml version="1.0" encoding="UTF-8"?>
97. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
98.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
99. <mapper namespace="com.example.demo.mapper.UserMapper">
100.    
101. </mapper><?xml version="1.0" encoding="UTF-8"?>
102. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
103.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
104. <mapper namespace="com.example.demo.mapper.UserMapper">
105.    
106. </mapper>return 0;<?xml version="1.0" encoding="UTF-8"?>
107. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
108.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
109. <mapper namespace="com.example.demo.mapper.UserMapper">
110.    
111. </mapper><?xml version="1.0" encoding="UTF-8"?>
112. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
113.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
114. <mapper namespace="com.example.demo.mapper.UserMapper">
115.    
116. </mapper>}<?xml version="1.0" encoding="UTF-8"?>
117. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
118.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
119. <mapper namespace="com.example.demo.mapper.UserMapper">
120.    
121. </mapper><?xml version="1.0" encoding="UTF-8"?>
122. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
123.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
124. <mapper namespace="com.example.demo.mapper.UserMapper">
125.    
126. </mapper>userService.insert2(user);<?xml version="1.0" encoding="UTF-8"?>
127. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
128.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
129. <mapper namespace="com.example.demo.mapper.UserMapper">
130.    
131. </mapper><?xml version="1.0" encoding="UTF-8"?>
132. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
133.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
134. <mapper namespace="com.example.demo.mapper.UserMapper">
135.    
136. </mapper>return user.getUserId();<?xml version="1.0" encoding="UTF-8"?>
137. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
138.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
139. <mapper namespace="com.example.demo.mapper.UserMapper">
140.    
141. </mapper>}

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4.1.2 添加 service 实现代码

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>public void insert2(User user) {<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>userMapper.insert2(user);<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>}

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4.1.3 添加 mapper 接口

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>void insert2(User user);

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4.1.4 添加 xml

注意: 如果要返回自增id, 就不能像普通增加那样写xml


正确写法:

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper>  insert into user values (null,#{username}, #{password});<?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>

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• useGeneratedKeys: 这个会取出数据库内部生成的主键, 默认值是false
  
• keyColumn: 设置生成键值在表中的列名, 在某些数据库中, 当主键列不是表中第一列的时候, 是必须设置的.如果生成列不止一个, 可以用逗号分隔多个属性名称
  
• keyProperty: 指定能够唯一标识对象的属性, 默认值: 未设置(unset), .如果生成列不止一个, 可以用逗号分隔多个属性名称
  

  4.1.5 测试代码



4.2 一对一的表映射

4.2.1 xml中具体的实现

一对一的表映射要使用  标签, 具体实现

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper><?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper><?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper><?xml version="1.0" encoding="UTF-8"?>
27. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
28.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
29. <mapper namespace="com.example.demo.mapper.UserMapper">
30.    
31. </mapper><?xml version="1.0" encoding="UTF-8"?>
32. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
33.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
34. <mapper namespace="com.example.demo.mapper.UserMapper">
35.    
36. </mapper><?xml version="1.0" encoding="UTF-8"?>
37. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
38.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
39. <mapper namespace="com.example.demo.mapper.UserMapper">
40.    
41. </mapper><?xml version="1.0" encoding="UTF-8"?>
42. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
43.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
44. <mapper namespace="com.example.demo.mapper.UserMapper">
45.    
46. </mapper><?xml version="1.0" encoding="UTF-8"?>
47. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
48.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
49. <mapper namespace="com.example.demo.mapper.UserMapper">
50.    
51. </mapper><?xml version="1.0" encoding="UTF-8"?>
52. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
53.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
54. <mapper namespace="com.example.demo.mapper.UserMapper">
55.    
56. </mapper><?xml version="1.0" encoding="UTF-8"?>
57. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
58.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
59. <mapper namespace="com.example.demo.mapper.UserMapper">
60.    
61. </mapper><?xml version="1.0" encoding="UTF-8"?>
62. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
63.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
64. <mapper namespace="com.example.demo.mapper.UserMapper">
65.    
66. </mapper><?xml version="1.0" encoding="UTF-8"?>
67. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
68.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
69. <mapper namespace="com.example.demo.mapper.UserMapper">
70.    
71. </mapper><?xml version="1.0" encoding="UTF-8"?>
72. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
73.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
74. <mapper namespace="com.example.demo.mapper.UserMapper">
75.    
76. </mapper><?xml version="1.0" encoding="UTF-8"?>
77. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
78.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
79. <mapper namespace="com.example.demo.mapper.UserMapper">
80.    
81. </mapper><?xml version="1.0" encoding="UTF-8"?>
82. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
83.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
84. <mapper namespace="com.example.demo.mapper.UserMapper">
85.    
86. </mapper><?xml version="1.0" encoding="UTF-8"?>
87. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
88.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
89. <mapper namespace="com.example.demo.mapper.UserMapper">
90.    
91. </mapper><?xml version="1.0" encoding="UTF-8"?>
92. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
93.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
94. <mapper namespace="com.example.demo.mapper.UserMapper">
95.    
96. </mapper><?xml version="1.0" encoding="UTF-8"?>
97. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
98.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
99. <mapper namespace="com.example.demo.mapper.UserMapper">
100.    
101. </mapper><?xml version="1.0" encoding="UTF-8"?>
102. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
103.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
104. <mapper namespace="com.example.demo.mapper.UserMapper">
105.    
106. </mapper><?xml version="1.0" encoding="UTF-8"?>
107. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
108.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
109. <mapper namespace="com.example.demo.mapper.UserMapper">
110.    
111. </mapper><?xml version="1.0" encoding="UTF-8"?>
112. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
113.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
114. <mapper namespace="com.example.demo.mapper.UserMapper">
115.    
116. </mapper><?xml version="1.0" encoding="UTF-8"?>
117. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
118.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
119. <mapper namespace="com.example.demo.mapper.UserMapper">
120.    
121. </mapper><?xml version="1.0" encoding="UTF-8"?>
122. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
123.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
124. <mapper namespace="com.example.demo.mapper.UserMapper">
125.    
126. </mapper><?xml version="1.0" encoding="UTF-8"?>
127. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
128.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
129. <mapper namespace="com.example.demo.mapper.UserMapper">
130.    
131. </mapper><?xml version="1.0" encoding="UTF-8"?>
132. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
133.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
134. <mapper namespace="com.example.demo.mapper.UserMapper">
135.    
136. </mapper><?xml version="1.0" encoding="UTF-8"?>
137. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
138.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
139. <mapper namespace="com.example.demo.mapper.UserMapper">
140.    
141. </mapper><?xml version="1.0" encoding="UTF-8"?>
142. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
143.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
144. <mapper namespace="com.example.demo.mapper.UserMapper">
145.    
146. </mapper><?xml version="1.0" encoding="UTF-8"?>
147. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
148.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
149. <mapper namespace="com.example.demo.mapper.UserMapper">
150.    
151. </mapper><?xml version="1.0" encoding="UTF-8"?>
152. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
153.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
154. <mapper namespace="com.example.demo.mapper.UserMapper">
155.    
156. </mapper>select b.*,u.userId u_userId,u.username u_username,u.password u_password from blog b left join user u on u.userId=b.userId<?xml version="1.0" encoding="UTF-8"?>
157. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
158.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
159. <mapper namespace="com.example.demo.mapper.UserMapper">
160.    
161. </mapper>

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  注意事项:
  

• property 属性: 指定 Blog 表中对应的属性名, 与实体类一致, 这里是user
  
• resultMap 属性: 指定关联的结果集映射, 将基于该映射配置来组织用户数据
  
• columnPrefix 属性: 绑定一对一对象时, 多表前缀, 作用防止多张表出现相同字段查询的问题
  

  4.2.2 Blog 实体类

1. @Datapublic class Blog {<?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>public int blogId;<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper>public String title;<?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>public String content;<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>public Timestamp postTime;<?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper>public int userId;<?xml version="1.0" encoding="UTF-8"?>
27. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
28.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
29. <mapper namespace="com.example.demo.mapper.UserMapper">
30.    
31. </mapper>public User user;}

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4.2.3 添加 controll

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>@RequestMapping("/getall")<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper>public List getAll() {<?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper><?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>return userService.getAll();<?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper>}

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4.2.4 添加 service

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>public List getAll() {<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>return userMapper.getAll();<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>}

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4.2.5 添加 mapper

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>List getAll();

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4.2.6 测试运行


4.3 一对多的表映射

4.3.1 xml中具体的实现

一对多使用  标签, 用法和 相同

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper><?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper><?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper><?xml version="1.0" encoding="UTF-8"?>
27. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
28.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
29. <mapper namespace="com.example.demo.mapper.UserMapper">
30.    
31. </mapper><?xml version="1.0" encoding="UTF-8"?>
32. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
33.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
34. <mapper namespace="com.example.demo.mapper.UserMapper">
35.    
36. </mapper><?xml version="1.0" encoding="UTF-8"?>
37. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
38.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
39. <mapper namespace="com.example.demo.mapper.UserMapper">
40.    
41. </mapper><?xml version="1.0" encoding="UTF-8"?>
42. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
43.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
44. <mapper namespace="com.example.demo.mapper.UserMapper">
45.    
46. </mapper><?xml version="1.0" encoding="UTF-8"?>
47. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
48.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
49. <mapper namespace="com.example.demo.mapper.UserMapper">
50.    
51. </mapper><?xml version="1.0" encoding="UTF-8"?>
52. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
53.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
54. <mapper namespace="com.example.demo.mapper.UserMapper">
55.    
56. </mapper><?xml version="1.0" encoding="UTF-8"?>
57. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
58.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
59. <mapper namespace="com.example.demo.mapper.UserMapper">
60.    
61. </mapper><?xml version="1.0" encoding="UTF-8"?>
62. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
63.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
64. <mapper namespace="com.example.demo.mapper.UserMapper">
65.    
66. </mapper><?xml version="1.0" encoding="UTF-8"?>
67. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
68.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
69. <mapper namespace="com.example.demo.mapper.UserMapper">
70.    
71. </mapper><?xml version="1.0" encoding="UTF-8"?>
72. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
73.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
74. <mapper namespace="com.example.demo.mapper.UserMapper">
75.    
76. </mapper><?xml version="1.0" encoding="UTF-8"?>
77. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
78.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
79. <mapper namespace="com.example.demo.mapper.UserMapper">
80.    
81. </mapper><?xml version="1.0" encoding="UTF-8"?>
82. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
83.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
84. <mapper namespace="com.example.demo.mapper.UserMapper">
85.    
86. </mapper><?xml version="1.0" encoding="UTF-8"?>
87. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
88.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
89. <mapper namespace="com.example.demo.mapper.UserMapper">
90.    
91. </mapper><?xml version="1.0" encoding="UTF-8"?>
92. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
93.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
94. <mapper namespace="com.example.demo.mapper.UserMapper">
95.    
96. </mapper>select b.*,u.username u_username,u.userId u_userId,u.password u_password from blog b left join user u on b.userId=u.userId where u.userId=#{userId}<?xml version="1.0" encoding="UTF-8"?>
97. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
98.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
99. <mapper namespace="com.example.demo.mapper.UserMapper">
100.    
101. </mapper>

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4.3.2 添加 controller

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>@RequestMapping("/getUserById")<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper>public List getUserById(Integer userId) {<?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper><?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>return userService.getUserById(userId);<?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper>}

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4.3.3 添加 service

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>public List getUserById(Integer userId) {<?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>return userMapper.getUserById(userId);<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>}

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4.3.4 添加 mapper接口

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper>List getUserById(Integer userId);

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4.3.5 测试运行


5. MyBatis 的一些注意事项

5.1 参数占位符 #{} 和 ${}

   

• #{} : 预编译处理
  
• ${} : 字符直接替换
  

  编译预处理: MyBatis 在处理 #{} 时, 会将SQL 中的 #{} 替换为 ? 号, 使用 PreparedStatement 的 set 方法来赋值.

字符直接替换: MyBatis 在处理 ${} 时, 就是把 ${} 替换成变量的值.(缺点SQL注入)

注意: 当使用 #{} 的时候, 传递值为 String 则会加单引号. 使用${}的时候, 就不会加单引号
5.1.1 ${} 的优点

在对一些商品进行排序的时候, 使用${}就可以, 而使用#{}就不行

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>select * from user order by userId ${sort};<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>

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5.2 SQL 注入问题

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper>  select * from user where username= '${username}' and password='${password}'<?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>

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当注入 'or 1='1 时, 所有的信息就暴露了

需要用户传递的就尽量使用 #{}, 程序员自己传递的就可以使用 ${}
5.3 like 查询

like 使用 #{} 会报错
例如一段sql代码
select * from user where username like '%#{username}%';
当username=admin 相当于
select * from user where username like '%'admin'%'
这里也不能直接使用 ${}.
可以使用mysql内置函数 concat() 来处理

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>select * from user where username like concat('%',#{username},'%')<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper>

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5.4 实体类中的字段和mysql中的字段不匹配


例如:
这里就查询不到 name了

除了把名字改过来, 还可以使用 resultMap

1.         <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper><?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper><?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper><?xml version="1.0" encoding="UTF-8"?>
27. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
28.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
29. <mapper namespace="com.example.demo.mapper.UserMapper">
30.    
31. </mapper><?xml version="1.0" encoding="UTF-8"?>
32. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
33.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
34. <mapper namespace="com.example.demo.mapper.UserMapper">
35.    
36. </mapper><?xml version="1.0" encoding="UTF-8"?>
37. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
38.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
39. <mapper namespace="com.example.demo.mapper.UserMapper">
40.    
41. </mapper><?xml version="1.0" encoding="UTF-8"?>
42. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
43.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
44. <mapper namespace="com.example.demo.mapper.UserMapper">
45.    
46. </mapper><?xml version="1.0" encoding="UTF-8"?>
47. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
48.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
49. <mapper namespace="com.example.demo.mapper.UserMapper">
50.    
51. </mapper><?xml version="1.0" encoding="UTF-8"?>
52. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
53.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
54. <mapper namespace="com.example.demo.mapper.UserMapper">
55.    
56. </mapper><?xml version="1.0" encoding="UTF-8"?>
57. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
58.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
59. <mapper namespace="com.example.demo.mapper.UserMapper">
60.    
61. </mapper><?xml version="1.0" encoding="UTF-8"?>
62. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
63.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
64. <mapper namespace="com.example.demo.mapper.UserMapper">
65.    
66. </mapper><?xml version="1.0" encoding="UTF-8"?>
67. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
68.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
69. <mapper namespace="com.example.demo.mapper.UserMapper">
70.    
71. </mapper>select * from user<?xml version="1.0" encoding="UTF-8"?>
72. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
73.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
74. <mapper namespace="com.example.demo.mapper.UserMapper">
75.    
76. </mapper>

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注意这里的resultMap的写法

5.5 想要在控制台查看 mybatis 的日志

在配置文件中添加代码

1. logging.level.com.example.demo=debug
2. mybaits.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

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通过这样配置就能查看日志了

5.6 编写 MyBatis 更方便的插件

搜索 MyBatisX

下载之后 重启Idea
有这种鸟就是安装好了

6. 动态 SQL

6.1 if 标签

在填写表单的时候 经常会有一些字段必须要填写, 一些字段不必要填写, 那么这种情况就需要用的动态SQL的if标签
xml的演示

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>insert into blog(<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper><?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper>title,<?xml version="1.0" encoding="UTF-8"?>
27. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
28.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
29. <mapper namespace="com.example.demo.mapper.UserMapper">
30.    
31. </mapper><?xml version="1.0" encoding="UTF-8"?>
32. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
33.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
34. <mapper namespace="com.example.demo.mapper.UserMapper">
35.    
36. </mapper><?xml version="1.0" encoding="UTF-8"?>
37. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
38.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
39. <mapper namespace="com.example.demo.mapper.UserMapper">
40.    
41. </mapper><?xml version="1.0" encoding="UTF-8"?>
42. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
43.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
44. <mapper namespace="com.example.demo.mapper.UserMapper">
45.    
46. </mapper>content,<?xml version="1.0" encoding="UTF-8"?>
47. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
48.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
49. <mapper namespace="com.example.demo.mapper.UserMapper">
50.    
51. </mapper><?xml version="1.0" encoding="UTF-8"?>
52. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
53.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
54. <mapper namespace="com.example.demo.mapper.UserMapper">
55.    
56. </mapper><?xml version="1.0" encoding="UTF-8"?>
57. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
58.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
59. <mapper namespace="com.example.demo.mapper.UserMapper">
60.    
61. </mapper><?xml version="1.0" encoding="UTF-8"?>
62. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
63.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
64. <mapper namespace="com.example.demo.mapper.UserMapper">
65.    
66. </mapper>postTime,userId) values (#{title},<?xml version="1.0" encoding="UTF-8"?>
67. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
68.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
69. <mapper namespace="com.example.demo.mapper.UserMapper">
70.    
71. </mapper><?xml version="1.0" encoding="UTF-8"?>
72. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
73.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
74. <mapper namespace="com.example.demo.mapper.UserMapper">
75.    
76. </mapper><?xml version="1.0" encoding="UTF-8"?>
77. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
78.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
79. <mapper namespace="com.example.demo.mapper.UserMapper">
80.    
81. </mapper><?xml version="1.0" encoding="UTF-8"?>
82. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
83.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
84. <mapper namespace="com.example.demo.mapper.UserMapper">
85.    
86. </mapper>#{content},<?xml version="1.0" encoding="UTF-8"?>
87. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
88.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
89. <mapper namespace="com.example.demo.mapper.UserMapper">
90.    
91. </mapper><?xml version="1.0" encoding="UTF-8"?>
92. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
93.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
94. <mapper namespace="com.example.demo.mapper.UserMapper">
95.    
96. </mapper><?xml version="1.0" encoding="UTF-8"?>
97. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
98.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
99. <mapper namespace="com.example.demo.mapper.UserMapper">
100.    
101. </mapper><?xml version="1.0" encoding="UTF-8"?>
102. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
103.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
104. <mapper namespace="com.example.demo.mapper.UserMapper">
105.    
106. </mapper>#{postTime},#{userId})<?xml version="1.0" encoding="UTF-8"?>
107. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
108.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
109. <mapper namespace="com.example.demo.mapper.UserMapper">
110.    
111. </mapper>

复制代码

注意这里的 if标签后面的test中的content是传入的属性,不是数据库中的字段.
6.2 trim 标签

当所有字段都是非必填项, 此时使用 if 标签就满足不了了
如 title是必填项, 后面都是非必填项, 此时sql拼装出来 就会变成
insert into blog(title,) values (title,) 这里的逗号就会导致sql报错.
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.demo.mapper.UserMapper">
   
</mapper>标签中有如下属性:
  

• prefix: 表示整个语句块, 以prefix的值作为前缀
  
• suffix: 表示整个语句块, 以suffix的值作为后缀
  
• prefixOverrides: prefixOverrides的值表示整个语句块要去掉的前缀
  
• suffixOverrides: suffixOverrides的值表示整个语句块要去掉的后缀
  

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper>insert into blog<?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper><?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper><?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper><?xml version="1.0" encoding="UTF-8"?>
27. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
28.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
29. <mapper namespace="com.example.demo.mapper.UserMapper">
30.    
31. </mapper><?xml version="1.0" encoding="UTF-8"?>
32. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
33.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
34. <mapper namespace="com.example.demo.mapper.UserMapper">
35.    
36. </mapper><?xml version="1.0" encoding="UTF-8"?>
37. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
38.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
39. <mapper namespace="com.example.demo.mapper.UserMapper">
40.    
41. </mapper><?xml version="1.0" encoding="UTF-8"?>
42. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
43.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
44. <mapper namespace="com.example.demo.mapper.UserMapper">
45.    
46. </mapper><?xml version="1.0" encoding="UTF-8"?>
47. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
48.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
49. <mapper namespace="com.example.demo.mapper.UserMapper">
50.    
51. </mapper><?xml version="1.0" encoding="UTF-8"?>
52. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
53.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
54. <mapper namespace="com.example.demo.mapper.UserMapper">
55.    
56. </mapper>title,<?xml version="1.0" encoding="UTF-8"?>
57. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
58.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
59. <mapper namespace="com.example.demo.mapper.UserMapper">
60.    
61. </mapper><?xml version="1.0" encoding="UTF-8"?>
62. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
63.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
64. <mapper namespace="com.example.demo.mapper.UserMapper">
65.    
66. </mapper><?xml version="1.0" encoding="UTF-8"?>
67. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
68.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
69. <mapper namespace="com.example.demo.mapper.UserMapper">
70.    
71. </mapper><?xml version="1.0" encoding="UTF-8"?>
72. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
73.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
74. <mapper namespace="com.example.demo.mapper.UserMapper">
75.    
76. </mapper><?xml version="1.0" encoding="UTF-8"?>
77. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
78.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
79. <mapper namespace="com.example.demo.mapper.UserMapper">
80.    
81. </mapper><?xml version="1.0" encoding="UTF-8"?>
82. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
83.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
84. <mapper namespace="com.example.demo.mapper.UserMapper">
85.    
86. </mapper><?xml version="1.0" encoding="UTF-8"?>
87. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
88.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
89. <mapper namespace="com.example.demo.mapper.UserMapper">
90.    
91. </mapper><?xml version="1.0" encoding="UTF-8"?>
92. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
93.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
94. <mapper namespace="com.example.demo.mapper.UserMapper">
95.    
96. </mapper><?xml version="1.0" encoding="UTF-8"?>
97. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
98.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
99. <mapper namespace="com.example.demo.mapper.UserMapper">
100.    
101. </mapper><?xml version="1.0" encoding="UTF-8"?>
102. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
103.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
104. <mapper namespace="com.example.demo.mapper.UserMapper">
105.    
106. </mapper>content,<?xml version="1.0" encoding="UTF-8"?>
107. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
108.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
109. <mapper namespace="com.example.demo.mapper.UserMapper">
110.    
111. </mapper><?xml version="1.0" encoding="UTF-8"?>
112. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
113.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
114. <mapper namespace="com.example.demo.mapper.UserMapper">
115.    
116. </mapper><?xml version="1.0" encoding="UTF-8"?>
117. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
118.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
119. <mapper namespace="com.example.demo.mapper.UserMapper">
120.    
121. </mapper><?xml version="1.0" encoding="UTF-8"?>
122. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
123.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
124. <mapper namespace="com.example.demo.mapper.UserMapper">
125.    
126. </mapper><?xml version="1.0" encoding="UTF-8"?>
127. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
128.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
129. <mapper namespace="com.example.demo.mapper.UserMapper">
130.    
131. </mapper><?xml version="1.0" encoding="UTF-8"?>
132. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
133.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
134. <mapper namespace="com.example.demo.mapper.UserMapper">
135.    
136. </mapper><?xml version="1.0" encoding="UTF-8"?>
137. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
138.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
139. <mapper namespace="com.example.demo.mapper.UserMapper">
140.    
141. </mapper><?xml version="1.0" encoding="UTF-8"?>
142. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
143.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
144. <mapper namespace="com.example.demo.mapper.UserMapper">
145.    
146. </mapper><?xml version="1.0" encoding="UTF-8"?>
147. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
148.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
149. <mapper namespace="com.example.demo.mapper.UserMapper">
150.    
151. </mapper><?xml version="1.0" encoding="UTF-8"?>
152. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
153.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
154. <mapper namespace="com.example.demo.mapper.UserMapper">
155.    
156. </mapper>postTime,<?xml version="1.0" encoding="UTF-8"?>
157. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
158.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
159. <mapper namespace="com.example.demo.mapper.UserMapper">
160.    
161. </mapper><?xml version="1.0" encoding="UTF-8"?>
162. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
163.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
164. <mapper namespace="com.example.demo.mapper.UserMapper">
165.    
166. </mapper><?xml version="1.0" encoding="UTF-8"?>
167. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
168.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
169. <mapper namespace="com.example.demo.mapper.UserMapper">
170.    
171. </mapper><?xml version="1.0" encoding="UTF-8"?>
172. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
173.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
174. <mapper namespace="com.example.demo.mapper.UserMapper">
175.    
176. </mapper><?xml version="1.0" encoding="UTF-8"?>
177. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
178.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
179. <mapper namespace="com.example.demo.mapper.UserMapper">
180.    
181. </mapper><?xml version="1.0" encoding="UTF-8"?>
182. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
183.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
184. <mapper namespace="com.example.demo.mapper.UserMapper">
185.    
186. </mapper><?xml version="1.0" encoding="UTF-8"?>
187. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
188.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
189. <mapper namespace="com.example.demo.mapper.UserMapper">
190.    
191. </mapper><?xml version="1.0" encoding="UTF-8"?>
192. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
193.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
194. <mapper namespace="com.example.demo.mapper.UserMapper">
195.    
196. </mapper><?xml version="1.0" encoding="UTF-8"?>
197. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
198.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
199. <mapper namespace="com.example.demo.mapper.UserMapper">
200.    
201. </mapper><?xml version="1.0" encoding="UTF-8"?>
202. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
203.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
204. <mapper namespace="com.example.demo.mapper.UserMapper">
205.    
206. </mapper>userId,<?xml version="1.0" encoding="UTF-8"?>
207. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
208.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
209. <mapper namespace="com.example.demo.mapper.UserMapper">
210.    
211. </mapper><?xml version="1.0" encoding="UTF-8"?>
212. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
213.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
214. <mapper namespace="com.example.demo.mapper.UserMapper">
215.    
216. </mapper><?xml version="1.0" encoding="UTF-8"?>
217. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
218.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
219. <mapper namespace="com.example.demo.mapper.UserMapper">
220.    
221. </mapper><?xml version="1.0" encoding="UTF-8"?>
222. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
223.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
224. <mapper namespace="com.example.demo.mapper.UserMapper">
225.    
226. </mapper><?xml version="1.0" encoding="UTF-8"?>
227. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
228.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
229. <mapper namespace="com.example.demo.mapper.UserMapper">
230.    
231. </mapper><?xml version="1.0" encoding="UTF-8"?>
232. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
233.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
234. <mapper namespace="com.example.demo.mapper.UserMapper">
235.    
236. </mapper><?xml version="1.0" encoding="UTF-8"?>
237. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
238.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
239. <mapper namespace="com.example.demo.mapper.UserMapper">
240.    
241. </mapper>values<?xml version="1.0" encoding="UTF-8"?>
242. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
243.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
244. <mapper namespace="com.example.demo.mapper.UserMapper">
245.    
246. </mapper><?xml version="1.0" encoding="UTF-8"?>
247. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
248.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
249. <mapper namespace="com.example.demo.mapper.UserMapper">
250.    
251. </mapper><?xml version="1.0" encoding="UTF-8"?>
252. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
253.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
254. <mapper namespace="com.example.demo.mapper.UserMapper">
255.    
256. </mapper><?xml version="1.0" encoding="UTF-8"?>
257. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
258.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
259. <mapper namespace="com.example.demo.mapper.UserMapper">
260.    
261. </mapper><?xml version="1.0" encoding="UTF-8"?>
262. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
263.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
264. <mapper namespace="com.example.demo.mapper.UserMapper">
265.    
266. </mapper><?xml version="1.0" encoding="UTF-8"?>
267. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
268.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
269. <mapper namespace="com.example.demo.mapper.UserMapper">
270.    
271. </mapper><?xml version="1.0" encoding="UTF-8"?>
272. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
273.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
274. <mapper namespace="com.example.demo.mapper.UserMapper">
275.    
276. </mapper><?xml version="1.0" encoding="UTF-8"?>
277. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
278.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
279. <mapper namespace="com.example.demo.mapper.UserMapper">
280.    
281. </mapper><?xml version="1.0" encoding="UTF-8"?>
282. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
283.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
284. <mapper namespace="com.example.demo.mapper.UserMapper">
285.    
286. </mapper>#{title},<?xml version="1.0" encoding="UTF-8"?>
287. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
288.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
289. <mapper namespace="com.example.demo.mapper.UserMapper">
290.    
291. </mapper><?xml version="1.0" encoding="UTF-8"?>
292. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
293.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
294. <mapper namespace="com.example.demo.mapper.UserMapper">
295.    
296. </mapper><?xml version="1.0" encoding="UTF-8"?>
297. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
298.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
299. <mapper namespace="com.example.demo.mapper.UserMapper">
300.    
301. </mapper><?xml version="1.0" encoding="UTF-8"?>
302. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
303.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
304. <mapper namespace="com.example.demo.mapper.UserMapper">
305.    
306. </mapper><?xml version="1.0" encoding="UTF-8"?>
307. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
308.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
309. <mapper namespace="com.example.demo.mapper.UserMapper">
310.    
311. </mapper><?xml version="1.0" encoding="UTF-8"?>
312. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
313.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
314. <mapper namespace="com.example.demo.mapper.UserMapper">
315.    
316. </mapper><?xml version="1.0" encoding="UTF-8"?>
317. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
318.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
319. <mapper namespace="com.example.demo.mapper.UserMapper">
320.    
321. </mapper><?xml version="1.0" encoding="UTF-8"?>
322. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
323.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
324. <mapper namespace="com.example.demo.mapper.UserMapper">
325.    
326. </mapper><?xml version="1.0" encoding="UTF-8"?>
327. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
328.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
329. <mapper namespace="com.example.demo.mapper.UserMapper">
330.    
331. </mapper><?xml version="1.0" encoding="UTF-8"?>
332. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
333.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
334. <mapper namespace="com.example.demo.mapper.UserMapper">
335.    
336. </mapper>#{content},<?xml version="1.0" encoding="UTF-8"?>
337. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
338.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
339. <mapper namespace="com.example.demo.mapper.UserMapper">
340.    
341. </mapper><?xml version="1.0" encoding="UTF-8"?>
342. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
343.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
344. <mapper namespace="com.example.demo.mapper.UserMapper">
345.    
346. </mapper><?xml version="1.0" encoding="UTF-8"?>
347. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
348.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
349. <mapper namespace="com.example.demo.mapper.UserMapper">
350.    
351. </mapper><?xml version="1.0" encoding="UTF-8"?>
352. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
353.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
354. <mapper namespace="com.example.demo.mapper.UserMapper">
355.    
356. </mapper><?xml version="1.0" encoding="UTF-8"?>
357. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
358.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
359. <mapper namespace="com.example.demo.mapper.UserMapper">
360.    
361. </mapper><?xml version="1.0" encoding="UTF-8"?>
362. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
363.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
364. <mapper namespace="com.example.demo.mapper.UserMapper">
365.    
366. </mapper><?xml version="1.0" encoding="UTF-8"?>
367. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
368.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
369. <mapper namespace="com.example.demo.mapper.UserMapper">
370.    
371. </mapper><?xml version="1.0" encoding="UTF-8"?>
372. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
373.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
374. <mapper namespace="com.example.demo.mapper.UserMapper">
375.    
376. </mapper><?xml version="1.0" encoding="UTF-8"?>
377. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
378.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
379. <mapper namespace="com.example.demo.mapper.UserMapper">
380.    
381. </mapper><?xml version="1.0" encoding="UTF-8"?>
382. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
383.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
384. <mapper namespace="com.example.demo.mapper.UserMapper">
385.    
386. </mapper>#{postTime},<?xml version="1.0" encoding="UTF-8"?>
387. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
388.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
389. <mapper namespace="com.example.demo.mapper.UserMapper">
390.    
391. </mapper><?xml version="1.0" encoding="UTF-8"?>
392. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
393.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
394. <mapper namespace="com.example.demo.mapper.UserMapper">
395.    
396. </mapper><?xml version="1.0" encoding="UTF-8"?>
397. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
398.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
399. <mapper namespace="com.example.demo.mapper.UserMapper">
400.    
401. </mapper><?xml version="1.0" encoding="UTF-8"?>
402. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
403.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
404. <mapper namespace="com.example.demo.mapper.UserMapper">
405.    
406. </mapper><?xml version="1.0" encoding="UTF-8"?>
407. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
408.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
409. <mapper namespace="com.example.demo.mapper.UserMapper">
410.    
411. </mapper><?xml version="1.0" encoding="UTF-8"?>
412. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
413.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
414. <mapper namespace="com.example.demo.mapper.UserMapper">
415.    
416. </mapper><?xml version="1.0" encoding="UTF-8"?>
417. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
418.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
419. <mapper namespace="com.example.demo.mapper.UserMapper">
420.    
421. </mapper><?xml version="1.0" encoding="UTF-8"?>
422. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
423.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
424. <mapper namespace="com.example.demo.mapper.UserMapper">
425.    
426. </mapper><?xml version="1.0" encoding="UTF-8"?>
427. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
428.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
429. <mapper namespace="com.example.demo.mapper.UserMapper">
430.    
431. </mapper><?xml version="1.0" encoding="UTF-8"?>
432. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
433.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
434. <mapper namespace="com.example.demo.mapper.UserMapper">
435.    
436. </mapper>#{userId},<?xml version="1.0" encoding="UTF-8"?>
437. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
438.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
439. <mapper namespace="com.example.demo.mapper.UserMapper">
440.    
441. </mapper><?xml version="1.0" encoding="UTF-8"?>
442. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
443.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
444. <mapper namespace="com.example.demo.mapper.UserMapper">
445.    
446. </mapper><?xml version="1.0" encoding="UTF-8"?>
447. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
448.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
449. <mapper namespace="com.example.demo.mapper.UserMapper">
450.    
451. </mapper><?xml version="1.0" encoding="UTF-8"?>
452. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
453.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
454. <mapper namespace="com.example.demo.mapper.UserMapper">
455.    
456. </mapper><?xml version="1.0" encoding="UTF-8"?>
457. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
458.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
459. <mapper namespace="com.example.demo.mapper.UserMapper">
460.    
461. </mapper><?xml version="1.0" encoding="UTF-8"?>
462. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
463.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
464. <mapper namespace="com.example.demo.mapper.UserMapper">
465.    
466. </mapper>

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6.3 where 标签

如代码 select * from blog where userId=#{userId}
如果这里的 userId 是非必填项, 为空, 那么sql也会报错
下面的 标签也可以使用 替换。

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>select * from blog<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper><?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper><?xml version="1.0" encoding="UTF-8"?>
27. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
28.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
29. <mapper namespace="com.example.demo.mapper.UserMapper">
30.    
31. </mapper><?xml version="1.0" encoding="UTF-8"?>
32. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
33.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
34. <mapper namespace="com.example.demo.mapper.UserMapper">
35.    
36. </mapper><?xml version="1.0" encoding="UTF-8"?>
37. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
38.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
39. <mapper namespace="com.example.demo.mapper.UserMapper">
40.    
41. </mapper><?xml version="1.0" encoding="UTF-8"?>
42. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
43.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
44. <mapper namespace="com.example.demo.mapper.UserMapper">
45.    
46. </mapper><?xml version="1.0" encoding="UTF-8"?>
47. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
48.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
49. <mapper namespace="com.example.demo.mapper.UserMapper">
50.    
51. </mapper><?xml version="1.0" encoding="UTF-8"?>
52. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
53.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
54. <mapper namespace="com.example.demo.mapper.UserMapper">
55.    
56. </mapper><?xml version="1.0" encoding="UTF-8"?>
57. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
58.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
59. <mapper namespace="com.example.demo.mapper.UserMapper">
60.    
61. </mapper>blogId = #{blogId}<?xml version="1.0" encoding="UTF-8"?>
62. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
63.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
64. <mapper namespace="com.example.demo.mapper.UserMapper">
65.    
66. </mapper><?xml version="1.0" encoding="UTF-8"?>
67. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
68.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
69. <mapper namespace="com.example.demo.mapper.UserMapper">
70.    
71. </mapper><?xml version="1.0" encoding="UTF-8"?>
72. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
73.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
74. <mapper namespace="com.example.demo.mapper.UserMapper">
75.    
76. </mapper><?xml version="1.0" encoding="UTF-8"?>
77. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
78.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
79. <mapper namespace="com.example.demo.mapper.UserMapper">
80.    
81. </mapper><?xml version="1.0" encoding="UTF-8"?>
82. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
83.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
84. <mapper namespace="com.example.demo.mapper.UserMapper">
85.    
86. </mapper><?xml version="1.0" encoding="UTF-8"?>
87. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
88.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
89. <mapper namespace="com.example.demo.mapper.UserMapper">
90.    
91. </mapper><?xml version="1.0" encoding="UTF-8"?>
92. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
93.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
94. <mapper namespace="com.example.demo.mapper.UserMapper">
95.    
96. </mapper><?xml version="1.0" encoding="UTF-8"?>
97. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
98.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
99. <mapper namespace="com.example.demo.mapper.UserMapper">
100.    
101. </mapper><?xml version="1.0" encoding="UTF-8"?>
102. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
103.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
104. <mapper namespace="com.example.demo.mapper.UserMapper">
105.    
106. </mapper><?xml version="1.0" encoding="UTF-8"?>
107. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
108.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
109. <mapper namespace="com.example.demo.mapper.UserMapper">
110.    
111. </mapper>and userId = #{userId}<?xml version="1.0" encoding="UTF-8"?>
112. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
113.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
114. <mapper namespace="com.example.demo.mapper.UserMapper">
115.    
116. </mapper><?xml version="1.0" encoding="UTF-8"?>
117. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
118.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
119. <mapper namespace="com.example.demo.mapper.UserMapper">
120.    
121. </mapper><?xml version="1.0" encoding="UTF-8"?>
122. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
123.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
124. <mapper namespace="com.example.demo.mapper.UserMapper">
125.    
126. </mapper><?xml version="1.0" encoding="UTF-8"?>
127. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
128.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
129. <mapper namespace="com.example.demo.mapper.UserMapper">
130.    
131. </mapper><?xml version="1.0" encoding="UTF-8"?>
132. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
133.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
134. <mapper namespace="com.example.demo.mapper.UserMapper">
135.    
136. </mapper><?xml version="1.0" encoding="UTF-8"?>
137. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
138.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
139. <mapper namespace="com.example.demo.mapper.UserMapper">
140.    
141. </mapper>

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• 标签, 如果有查询条件就会生成where, 如果没有查询条件就不会生成where
  
• where会判断第一个条件前面有没有and, 如果有就会去掉.
  

  6.4 set 标签

更新的时候也会出现问题, 使用  标签来解决
set标签和where标签差不多

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>update user<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper><?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper><?xml version="1.0" encoding="UTF-8"?>
27. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
28.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
29. <mapper namespace="com.example.demo.mapper.UserMapper">
30.    
31. </mapper><?xml version="1.0" encoding="UTF-8"?>
32. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
33.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
34. <mapper namespace="com.example.demo.mapper.UserMapper">
35.    
36. </mapper><?xml version="1.0" encoding="UTF-8"?>
37. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
38.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
39. <mapper namespace="com.example.demo.mapper.UserMapper">
40.    
41. </mapper><?xml version="1.0" encoding="UTF-8"?>
42. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
43.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
44. <mapper namespace="com.example.demo.mapper.UserMapper">
45.    
46. </mapper><?xml version="1.0" encoding="UTF-8"?>
47. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
48.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
49. <mapper namespace="com.example.demo.mapper.UserMapper">
50.    
51. </mapper><?xml version="1.0" encoding="UTF-8"?>
52. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
53.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
54. <mapper namespace="com.example.demo.mapper.UserMapper">
55.    
56. </mapper><?xml version="1.0" encoding="UTF-8"?>
57. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
58.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
59. <mapper namespace="com.example.demo.mapper.UserMapper">
60.    
61. </mapper>username=#{username},<?xml version="1.0" encoding="UTF-8"?>
62. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
63.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
64. <mapper namespace="com.example.demo.mapper.UserMapper">
65.    
66. </mapper><?xml version="1.0" encoding="UTF-8"?>
67. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
68.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
69. <mapper namespace="com.example.demo.mapper.UserMapper">
70.    
71. </mapper><?xml version="1.0" encoding="UTF-8"?>
72. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
73.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
74. <mapper namespace="com.example.demo.mapper.UserMapper">
75.    
76. </mapper><?xml version="1.0" encoding="UTF-8"?>
77. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
78.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
79. <mapper namespace="com.example.demo.mapper.UserMapper">
80.    
81. </mapper><?xml version="1.0" encoding="UTF-8"?>
82. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
83.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
84. <mapper namespace="com.example.demo.mapper.UserMapper">
85.    
86. </mapper><?xml version="1.0" encoding="UTF-8"?>
87. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
88.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
89. <mapper namespace="com.example.demo.mapper.UserMapper">
90.    
91. </mapper><?xml version="1.0" encoding="UTF-8"?>
92. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
93.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
94. <mapper namespace="com.example.demo.mapper.UserMapper">
95.    
96. </mapper><?xml version="1.0" encoding="UTF-8"?>
97. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
98.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
99. <mapper namespace="com.example.demo.mapper.UserMapper">
100.    
101. </mapper><?xml version="1.0" encoding="UTF-8"?>
102. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
103.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
104. <mapper namespace="com.example.demo.mapper.UserMapper">
105.    
106. </mapper><?xml version="1.0" encoding="UTF-8"?>
107. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
108.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
109. <mapper namespace="com.example.demo.mapper.UserMapper">
110.    
111. </mapper>password=#{password},<?xml version="1.0" encoding="UTF-8"?>
112. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
113.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
114. <mapper namespace="com.example.demo.mapper.UserMapper">
115.    
116. </mapper><?xml version="1.0" encoding="UTF-8"?>
117. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
118.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
119. <mapper namespace="com.example.demo.mapper.UserMapper">
120.    
121. </mapper><?xml version="1.0" encoding="UTF-8"?>
122. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
123.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
124. <mapper namespace="com.example.demo.mapper.UserMapper">
125.    
126. </mapper><?xml version="1.0" encoding="UTF-8"?>
127. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
128.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
129. <mapper namespace="com.example.demo.mapper.UserMapper">
130.    
131. </mapper><?xml version="1.0" encoding="UTF-8"?>
132. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
133.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
134. <mapper namespace="com.example.demo.mapper.UserMapper">
135.    
136. </mapper><?xml version="1.0" encoding="UTF-8"?>
137. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
138.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
139. <mapper namespace="com.example.demo.mapper.UserMapper">
140.    
141. </mapper><?xml version="1.0" encoding="UTF-8"?>
142. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
143.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
144. <mapper namespace="com.example.demo.mapper.UserMapper">
145.    
146. </mapper>where userId=#{userId}<?xml version="1.0" encoding="UTF-8"?>
147. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
148.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
149. <mapper namespace="com.example.demo.mapper.UserMapper">
150.    
151. </mapper>

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6.5 foreach 标签

   标签有如下属性：
  

• collection：绑定⽅法参数中的集合，如 List，Set，Map或数组对象
  
• item：遍历时的每⼀个对象
  
• open：语句块开头的字符串
  
• close：语句块结束的字符串
  
• separator：每次遍历之间间隔的字符串
  

1. <?xml version="1.0" encoding="UTF-8"?>
2. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4. <mapper namespace="com.example.demo.mapper.UserMapper">
5.    
6. </mapper><?xml version="1.0" encoding="UTF-8"?>
7. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
8.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
9. <mapper namespace="com.example.demo.mapper.UserMapper">
10.    
11. </mapper><?xml version="1.0" encoding="UTF-8"?>
12. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
13.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
14. <mapper namespace="com.example.demo.mapper.UserMapper">
15.    
16. </mapper>delete from user where userId in<?xml version="1.0" encoding="UTF-8"?>
17. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
18.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
19. <mapper namespace="com.example.demo.mapper.UserMapper">
20.    
21. </mapper><?xml version="1.0" encoding="UTF-8"?>
22. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
23.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
24. <mapper namespace="com.example.demo.mapper.UserMapper">
25.    
26. </mapper><?xml version="1.0" encoding="UTF-8"?>
27. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
28.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
29. <mapper namespace="com.example.demo.mapper.UserMapper">
30.    
31. </mapper><?xml version="1.0" encoding="UTF-8"?>
32. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
33.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
34. <mapper namespace="com.example.demo.mapper.UserMapper">
35.    
36. </mapper><?xml version="1.0" encoding="UTF-8"?>
37. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
38.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
39. <mapper namespace="com.example.demo.mapper.UserMapper">
40.    
41. </mapper>#{item}<?xml version="1.0" encoding="UTF-8"?>
42. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
43.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
44. <mapper namespace="com.example.demo.mapper.UserMapper">
45.    
46. </mapper><?xml version="1.0" encoding="UTF-8"?>
47. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
48.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
49. <mapper namespace="com.example.demo.mapper.UserMapper">
50.    
51. </mapper><?xml version="1.0" encoding="UTF-8"?>
52. <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
53.         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
54. <mapper namespace="com.example.demo.mapper.UserMapper">
55.    
56. </mapper>

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