学习笔记——Mybatis核心配置文件概述及根标签

2023-01-09
一、Mybatis核心配置文件概述及根标签
1、核心配置文件的概述（即“mybatis-config.xml”）
MyBatis的配置文件包含了会深深影响MyBatis行为的设置和属性信息。
2、标签
（1）configuration（配置）
（2）properties（属性）
作用：定义或引入外部属性文件
在“day02_mybatis.src.main.resources”文件夹下创建“数据库的连接文件”，命名为“db.properties”
①db.properties里面的内容

1. #里面存放的数据格式为key=value
2. db.driver=com.mysql.cj.jdbc.Driver
3. db.url=jdbc:mysql://localhost:3306/db220106?serverTimezone=UTC
4. db.username=设置自己的数据库的用户名称
5. db.password=数据库的密码

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②“day02_mybatis.src.main.resources”下的“mybatis-config.xml”中的内容

1. <?xml version="1.0" encoding="UTF-8" ?>
2. <!DOCTYPE configuration
3. <settings>
4. <typeAliases>
5.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
6. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
7. </settings>PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
8. <settings>
9. <typeAliases>
10.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
11. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
12. </settings>"https://mybatis.org/dtd/mybatis-3-config.dtd">
13. <configuration>
15.     <properties resource="db.properties"></properties>
17.     <environments default="development">
18. <settings>
19. <typeAliases>
20.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
21. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
22. </settings><environment id="development">
23. <settings>
24. <typeAliases>
25.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
26. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
27. </settings>    <transactionManager type="JDBC"/>
28. <settings>
29. <typeAliases>
30.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
31. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
32. </settings>    <dataSource type="POOLED">
33. <settings>
34. <typeAliases>
35.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
36. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
37. </settings><settings>
38. <typeAliases>
39.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
40. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
41. </settings><property name="driver" value="${db.driver}"/>
42. <settings>
43. <typeAliases>
44.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
45. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
46. </settings><settings>
47. <typeAliases>
48.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
49. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
50. </settings><property name="url" value="${db.url}"/>
51. <settings>
52. <typeAliases>
53.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
54. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
55. </settings><settings>
56. <typeAliases>
57.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
58. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
59. </settings><property name="username" value="${db.username}"/>
60. <settings>
61. <typeAliases>
62.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
63. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
64. </settings><settings>
65. <typeAliases>
66.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
67. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
68. </settings><property name="password" value="${db.password}"/>
69. <settings>
70. <typeAliases>
71.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
72. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
73. </settings>    </dataSource>
74. <settings>
75. <typeAliases>
76.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
77. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
78. </settings></environment>
79.     </environments>
80.    
81.     <mappers>
82. <settings>
83. <typeAliases>
84.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
85. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
86. </settings><mapper resource="mapper/EmployeeMapper.xml"/>
87.     </mappers>
88. </configuration>

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③“day02_mybatis.src.test.java.TestMybatis”中的代码

1. import com.hh.mybatis.mapper.EmployeeMapper;
2. import com.hh.mybatis.pojo.Employee;
3. import org.apache.ibatis.io.Resources;
4. import org.apache.ibatis.session.SqlSession;
5. import org.apache.ibatis.session.SqlSessionFactory;
6. import org.apache.ibatis.session.SqlSessionFactoryBuilder;
7. import org.junit.Test;
9. import java.io.IOException;
10. import java.io.InputStream;
12. public class TestMybatis {
13.     @Test
14.     public void TestMybatis(){
15. <settings>
16. <typeAliases>
17.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
18. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
19. </settings>try {
20. <settings>
21. <typeAliases>
22.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
23. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
24. </settings>    String resource = "mybatis-config.xml";
25. <settings>
26. <typeAliases>
27.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
28. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
29. </settings>    InputStream inputStream = Resources.getResourceAsStream(resource);
30. <settings>
31. <typeAliases>
32.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
33. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
34. </settings>    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
35. <settings>
36. <typeAliases>
37.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
38. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
39. </settings>    //通过sqlSessionFactory获取sqlSession对象
40. <settings>
41. <typeAliases>
42.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
43. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
44. </settings>    SqlSession sqlSession = sqlSessionFactory.openSession();
45. <settings>
46. <typeAliases>
47.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
48. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
49. </settings>    //获取EmployeeMapper的代理对象
50. <settings>
51. <typeAliases>
52.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
53. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
54. </settings>    EmployeeMapper employeeMapper = sqlSession.getMapper(EmployeeMapper.class);
55. <settings>
56. <typeAliases>
57.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
58. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
59. </settings>    System.out.println("employeeMapper.getClass().getName() = " + employeeMapper.getClass().getName());
61. <settings>
62. <typeAliases>
63.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
64. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
65. </settings>    Employee employee = employeeMapper.selectEmployee(1);
66. <settings>
67. <typeAliases>
68.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
69. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
70. </settings>    System.out.println("employee = " + employee);
71. <settings>
72. <typeAliases>
73.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
74. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
75. </settings>} catch (IOException e) {
76. <settings>
77. <typeAliases>
78.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
79. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
80. </settings>    e.printStackTrace();
81. <settings>
82. <typeAliases>
83.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
84. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
85. </settings>}
86.     }
88. }

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④测试代码，代码OK
（3）settings（设置）
①作用：这是MyBatis中极为重要的调整设置，它们会改变MyBatis的运行行为
②例如：mapUnderscoreToCamelCase属性：表示是否开启驼峰命名自动映射，默认值是false，如设置true会自动将字段last_name与lastName属性自动映射。
③在“day02_mybatis.src.main.resources”下的“mybatis-config.xml”中的“”设置

1. <settings>
2. <typeAliases>
3.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
4. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
5. </settings>

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（4）typeAliases（类型别名）
①作用：类型别名可为java类型设置一个缩写名字。
②xml代码：

1. <settings>
2. <typeAliases>
3.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
4. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
5. </settings>

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其中的xml代码也可以简写为

1. <settings>
2. <typeAliases>
3.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
4. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
5. </settings>

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③之后，可以将“day02_mybatis.src.mian.resources.mapper”下的“EmployeeMapper.xml”中的“resultType”设置为“employee”,如下：

1. <settings>
2. <typeAliases>
3.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
4. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
5. </settings>    SELECT<settings>
6. <typeAliases>
7.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
8. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
9. </settings>    id,<settings>
10. <typeAliases>
11.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
12. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
13. </settings>    last_name,<settings>
14. <typeAliases>
15.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
16. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
17. </settings>    email,<settings>
18. <typeAliases>
19.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
20. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
21. </settings>    salary<settings>
22. <typeAliases>
23.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
24. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
25. </settings>FROM<settings>
26. <typeAliases>
27.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
28. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
29. </settings>    tbl_employee<settings>
30. <typeAliases>
31.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
32. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
33. </settings>WHERE<settings>
34. <typeAliases>
35.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
36. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
37. </settings>    id=#{empId}   

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（5）typeHandlers（类型处理器）
（6）objectFactory（对象工厂）
（7）plugins（插件）
（8）environments（环境配置）
①作用：设置数据库的连接环境
②实例xml代码

1. <settings>
2. <typeAliases>
3.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
4. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
5. </settings><settings>
6. <typeAliases>
7.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
8. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
9. </settings><settings>
10. <typeAliases>
11.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
12. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
13. </settings><settings>
14. <typeAliases>
15.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
16. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
17. </settings><settings>
18. <typeAliases>
19.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
20. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
21. </settings><settings>
22. <typeAliases>
23.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
24. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
25. </settings><settings>
26. <typeAliases>
27.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
28. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
29. </settings><settings>
30. <typeAliases>
31.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
32. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
33. </settings><settings>
34. <typeAliases>
35.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
36. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
37. </settings><settings>
38. <typeAliases>
39.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
40. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
41. </settings><settings>
42. <typeAliases>
43.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
44. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
45. </settings><settings>
46. <typeAliases>
47.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
48. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
49. </settings><settings>
50. <typeAliases>
51.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
52. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
53. </settings><settings>
54. <typeAliases>
55.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
56. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
57. </settings><settings>
58. <typeAliases>
59.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
60. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
61. </settings>  

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（9）databaseldProvider（数据库厂商标识）
（10）mappers（映射器）
 ①作用：设置映射文件路径
②xml代码：
例如：

1. <settings>
2. <typeAliases>
3.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
4. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
5. </settings><settings>
6. <typeAliases>
7.         <typeAlias type="com.hh.mybatis.pojo.Employee" alias="employee"></typeAlias>
8. </typeAliases><setting name="mapUnderscoreToCamelCase" value="true"/>
9. </settings>

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3、注意事项
核心配置中的子标签，是有顺序要求的。顺序如下：

 

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