JavaMyBatis 的在使用上的留意事项及其辨析

鼠扑发表于 2024-6-13 14:57:01

MyBatis 的在使用上的留意事项及其辨析

1. MyBatis 的在使用上的留意事项及其辨析

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目录

[*]1. MyBatis 的在使用上的留意事项及其辨析
[*]2. 准备工作
[*]3. #{ } 与 ${ } 的区别和使用
[*]{}

[*]3.1 什么情况下必须使用 $

[*]3.1.1 拼接表名
[*]3.1.2 批量删除
[*]3.1.3 模糊查询

[*]3.1.3.1 使用 ${ }的方式
[*]3.1.3.2 使用 #{ } 的方式

[*]4. typeAliases 别名定义的使用

[*]4.1 typeAliases 的第一种方式：typeAlias
[*]4.2 typeAliases 的第二种方式：package

[*]5. mappers 路径设置的使用

[*]5.1 mapper 标签下的 resource 属性的使用
[*]5.2 mapper 标签下的 url 属性的使用
[*]5.3 mapper 标签下的 class 属性的使用
[*]5.4 package 标签的使用

[*]6. 在 IDEA 中自定义配置文件模板
[*]7. 补充：插入数据时获取自动天生的主键的值
[*]8. 总结：
[*]{ } 与 ${ } 的区别和使用
[*]9. 最后：

2. 准备工作

数据表结构的计划，数据表名为：t_car
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642045-783599701.png
t_car 表中的数据信息：
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641986-781128621.png
在pom.xml 文件当中配置相关的依赖的 jar 包如下：
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641947-1701620315.png
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>com.rainbowsea</groupId>
<artifactId>mybatis-005-crud-blog</artifactId>
<version>1.0-SNAPSHOT</version>

<properties>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><maven.compiler.source>17</maven.compiler.source>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><maven.compiler.target>17</maven.compiler.target>
</properties>

<dependencies>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><dependency>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><groupId>org.mybatis</groupId>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><artifactId>mybatis</artifactId>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><version>3.5.10</version>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers></dependency>

<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><dependency>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><groupId>mysql</groupId>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><artifactId>mysql-connector-java</artifactId>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><version>8.0.30</version>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers></dependency>

<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><dependency>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><groupId>junit</groupId>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><artifactId>junit</artifactId>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><version>4.13.2</version>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><scope>test</scope>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers></dependency>

<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><dependency>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><groupId>ch.qos.logback</groupId>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><artifactId>logback-classic</artifactId>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><version>1.2.11</version>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers></dependency>
</dependencies>

</project>配置 logback 的配置文件，用于打印显示，我们的日记信息，方便我们查看我们的运行过程，效果。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642041-1125495524.png
<?xml version="1.0" encoding="UTF-8"?>

<configuration debug="false">

<appender name="STDOUT" >
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><encoder >
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{50} - %msg%n</pattern>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers></encoder>
</appender>

<logger name="com.apache.ibatis" level="TRACE"/>
<logger name="java.sql.Connection" level="DEBUG"/>
<logger name="java.sql.Statement" level="DEBUG"/>
<logger name="java.sql.PreparedStatement" level="DEBUG"/>

<root level="DEBUG">
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><appender-ref ref="STDOUT"/>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><appender-ref ref="FILE"/>
</root>

</configuration>配置 MyBatis 的核心配置文件，
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641967-1846611494.png
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

<typeAliases>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><package name="com.rainbowsea.mybatis.pojo"/>
</typeAliases>
<environments default="mybatis">

<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><environment id="mybatis">
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><transactionManager type="JDBC"/>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><dataSource type="POOLED">
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> <property name="username" value="root"/>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> <property name="password" value="MySQL123"/>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers></dataSource>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers></environment>
</environments>
<mappers>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mapper resource="CarMapper.xml"></mapper>
</mappers>
</configuration>对照 t_car 创建的ORM 映射的 Car 类
留意：在MyBatis 当中对应的ORM ，一般在框架里对应的 Bean实体类，一定要实现该 set 和 get 方法以及无参数构造方法，无法框架无法使用反射机制，进行操纵。
发起用包装类，如许可以防止 Null的问题，因为（简单类型 int num = null ，是不可以赋值为 null）的编译无法通过
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641978-244895684.png
package com.rainbowsea.mybatis.pojo;

public class Car {
// 数据库表当中的字段应该和pojo类的属性一一对应
// 建议使用包装类，这样可以防止null的问题
private Long id;
private String carNum;
private String brand;
private Double guidePrice;
private String produceTime;
private String carType;

public Car() {
}

public Car(Long id, String carNum, String brand, Double guidePrice, String produceTime, String carType) {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.id = id;
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.carNum = carNum;
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.brand = brand;
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.guidePrice = guidePrice;
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.produceTime = produceTime;
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.carType = carType;
}

@Override
public String toString() {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>return "Car{" +
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> "id=" + id +
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> ", carNum='" + carNum + '\'' +
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> ", brand='" + brand + '\'' +
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> ", guidePrice=" + guidePrice +
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> ", produceTime='" + produceTime + '\'' +
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> ", catType='" + carType + '\'' +
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> '}';
}

public Long getId() {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>return id;
}

public void setId(Long id) {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.id = id;
}

public String getCarNum() {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>return carNum;
}

public void setCarNum(String carNum) {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.carNum = carNum;
}

public String getBrand() {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>return brand;
}

public void setBrand(String brand) {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.brand = brand;
}

public Double getGuidePrice() {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>return guidePrice;
}

public void setGuidePrice(Double guidePrice) {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.guidePrice = guidePrice;
}

public String getProduceTime() {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>return produceTime;
}

public void setProduceTime(String produceTime) {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.produceTime = produceTime;
}

public String getcarType() {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>return carType;
}

public void setcarType(String catType) {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.carType = catType;
}
}对应操纵实现CRUD（增删改查）的接口(这里是：CarMapper接口)，在MyBtis 当中，关于 CRUD(增删改查)操纵的接口/实现类，都是 mapper 结尾的作为长期层，而在 MVC的三层架构中，则是以 dao 为后缀作为CRUD(增删改查)操纵的接口/实现类。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641901-518706743.png
package com.rainbowsea.mybatis.mapper;

import com.rainbowsea.mybatis.pojo.Car;

import java.util.List;

public interface CarMapper {

/**
* 新增 Car
* @param car
* @return
*/
int insert(Car car);

/**
* 根据id 删除 Car
* @param id
* @return
*/
int deleteById(Long id);

/**
* 修改汽车信息
* @param car
* @return
*/
int update(Car car);

/**
* 根据id查询汽车信息
* @param id
* @return
*/
Car selectById(Long id);

/**
* 获取所有的汽车信息
* @return
*/
List<Car> selectAll();
}获取 Sqlsession 对象的工具类的编写。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642102-1430185829.png
package com.rainbowsea.mybatis.utils;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;

public class SqlSessionUtil {
// 工具类的构造方法一般都是私有话化的
// 工具类中所有的方法都是静态的，直接类名即可调用，不需要 new 对象
// 为了防止new对象，构造方法私有化。

private SqlSessionUtil() {

}

private static SqlSessionFactory sessionFactory = null;

// 静态代码块，类加载时执行
// SqlSessionUtil 工具类在进行第一次加载的时候，解析mybatis-config.xml 文件，创建SqlSessionFactory对象。
static {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>// 获取到SqlSessionFactoryBuilder 对象
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();

<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>// 获取到SqlSessionFactory 对象
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>// SQlsessionFactory对象，一个SqlSessionFactory对应一个 environment, 一个environment通常是一个数据库
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>try {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>sessionFactory = sqlSessionFactoryBuilder.build(Resources.getResourceAsStream("mybatis-config.xml"),
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>"mybatis");
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>} catch (IOException e) {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>throw new RuntimeException(e);
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>}

}

/**
* 获取会话对象
* @return SqlSession
*/
public static SqlSession openSession() {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>// 获取到 SqlSession 对象
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>SqlSession sqlSession = sessionFactory.openSession();
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>return sqlSession;
}
}3. #{ } 与 ${ } 的区别和使用

[*]#{ } ：先编译 SQL 语句，再对占位符传值，底层是 PrepareedStatement 实现，可以防止 SQL 注入，比力常用
[*]${ }：先进行SQL语句的拼接，然后再对SQL语句进行编译，底层是 Statement 实现，这种方式存在 SQL注入现象，SQL注入的风险，简单的说就是，直接将传入的值拼接为了SQL语句，然后再实行的）。只有在需要进行SQL语句关键字拼接的情况下才会用到。
[*]简单的说一个区别就是：#{} 传的值是带有 '' 单引号的，而 ${} 传的值是（直接就是值，没有单引号，或者是双引号，两个都没有）
查验一下。
这里我们根据汽车的 car_type 查询，为新能源汽车的。多条记录
首先这里我们先使用 #{} ，传的是带有 '' 单引号的值 ——> '新能源'
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641863-641490551.png
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641986-242316792.png
package com.rainbowsea.mybatis.mapper;

import com.rainbowsea.mybatis.pojo.Car;

import java.util.List;

/**
* 封装汽车相关信息的pojo类，普通的Java类
*/
public interface CarMapper {

/**
* 根据汽车类型获取汽车信息
* @param carType
* @return
*/
List<Car> selectByCarType(String carType);

}<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.rainbowsea.mybatis.mapper.CarMapper">

<select id="selectByCarType" resultType="com.rainbowsea.mybatis.pojo.Car">
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>select id,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> car_num<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>as carNum,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> brand,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> guide_priceas guidePrice,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> produce_time as produceTime,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> car_type as carType
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>from t_car
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>where car_type = #{carType}
</select>

</mapper>运行Java步伐：
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642047-290766257.png
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641987-2003620165.png
查询乐成。
下面我们再实行用${} ，直接就是新能源的值，没有单引号，也没有双引号，就是直接就是——》新能源的值。运行结果如下：
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642057-580340346.png
比力上述#{}和 ?{} 的运行结果：
{}

https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642056-1844897779.png
${}
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641884-222111481.png
通过实行可以清楚的看到，sql 语句中是带有 ? 的，这个 ? 就是各人在JDBC中所学的占位符，专门用来接收值的。
把“新能源”以 String 类型的值，传递给 ? ，加上 '' 单引号，作为字符串传入进行，实行SQL语句
这就是 #{}，它会先进行sql语句的预编译，然后再给占位符传值。
而 ${} 是直接将我们的新能源作为值，传入给SQL语句的，留意 ${} 的方式是不会加单引号/双引号的，而是作为值，直接拼接到 SQL语句当中去了，但是，在我们这个查询的SQL当中，新能源就是必须要为字符串才行的，不然是无法实行SQL语句，是无法识别出来的。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642052-681366853.png
3.1 什么情况下必须使用 $

当需要进行 sql 语句关键字拼接的时候，简单的说就是当我们要使用 SQL语句当中的关键字的时候，以及要传的值，不要单引号/双引号的值的时候，就必须使用${ }
需求：通过向sql语句中注入asc或desc关键字，来完成数据的升序或降序排列。
根据数据表中的 produce_time日期时间进行排序。
因为这里我们使用到了 ASC / DESC 这两者都是 SQL语句当中的关键字，以是我们需要使用 ${} 的方式。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642083-28220460.png
package com.rainbowsea.mybatis.mapper;

import com.rainbowsea.mybatis.pojo.Car;

import java.util.List;

/**
* 封装汽车相关信息的pojo类，普通的Java类
*/
public interface CarMapper {

/**
* 查询所有的汽车信息，然后通过 asc 升序，desc 降序
* @param ascOrDesc
* @return
*/
List<Car> selectAllByAscOrDesc(String ascOrDesc);

}<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.rainbowsea.mybatis.mapper.CarMapper">

<select id="selectAllByAscOrDesc" resultType="com.rainbowsea.mybatis.pojo.Car">
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>select id,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> car_num<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>as carNum,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> brand,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> guide_priceas guidePrice,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> produce_time as produceTime,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> car_type as carType
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>from t_car
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>order by produce_time ${ascOrDesc}
</select>

</mapper>Java步伐运行测试：
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642035-148892562.png
public class TestCarMapper {

@Test
public void testSelectAllByAscOrDesc() {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>SqlSession sqlSession = SqlSessionUtil.openSession();
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>CarMapper mapper = sqlSession.getMapper(CarMapper.class);
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>List<Car> cars = mapper.selectAllByAscOrDesc("asc");
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>cars.forEach(car -> {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>System.out.println(car);
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>});

<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>sqlSession.close();
}

}如果换成 #{} ，将SQL 语句的关键字 asc 作为字符串的形式拼接到 SQL语句当中是会编译失败的了。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642040-286854377.png
3.1.1 拼接表名

业务背景：实际开发中，有的表数据量非常庞大，大概会接纳分表方式进行存储，比如每天天生一张表，表的名字与日期挂钩，例如：2022年8月1日天生的表：t_user20220108。2000年1月1日天生的表：t_user20000101。此时前端在进行查询的时候会提交一个具体的日期，比如前端提交的日期为：2000年1月1日，那么后端就会根据这个日期动态拼接表名为：t_user20000101。有了这个表名之后，将表名拼接到sql语句当中，返回查询结果。那么各人思考一下，拼接表名到sql语句当中应该使用#{} 还是 ${} 呢？
使用#{}会是如许：select * from 't_car'
使用${}会是如许：select * from t_car
向SQL语句当中拼接表名，就需要使用${}
实际业务当中，大概存在分表存储的数据的情况，因为一张表存的话，数据量太大了，查询效率比力低。
可以将这些数据有规律的分表存储，如许在查询的时候效率就比力高，因为扫描的数据量变小了
日记表，专门存储日记信息，如果t_long 只有一张表，这张表中每一天都会产生许多的log,逐步的，这个表中数据会许多，
怎么办理呢
可以每天天生一个新表，每张表以当天日期作为名称，例如：
t_log_202209801
t_log_20220902
你想知道某一天的日记信息怎么办呢？
假设本日20220901，那么直接查：t_log-20220901的表即可。
下面是我们的t_log_20220902 的数据表信息
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642087-208269535.png
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641987-1773439661.png
对应数据表的 POJO 类计划：
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642037-972423692.png
package com.rainbowsea.mybatis.pojo;

public class Log {
private Integer id;
private String log;
private String time;

public Log() {
}

public Log(Integer id, String log, String time) {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.id = id;
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.log = log;
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.time = time;
}

@Override
public String toString() {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>return "Log{" +
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> "id=" + id +
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> ", log='" + log + '\'' +
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> ", time='" + time + '\'' +
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> '}';
}

public Integer getId() {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>return id;
}

public void setId(Integer id) {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.id = id;
}

public String getLog() {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>return log;
}

public void setLog(String log) {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.log = log;
}

public String getTime() {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>return time;
}

public void setTime(String time) {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>this.time = time;
}
}对应的LogMapper 的接口信息编写。
首先我们使用 ${} 的方式测试运行。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641981-1761718441.png
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642103-1225339126.png
package com.rainbowsea.mybatis.mapper;

import com.rainbowsea.mybatis.pojo.Log;

import java.util.List;

public interface LogMapper {

/**
* 根据日期查询不同的表，获取表中所有的日志
*
* @param date
* @return
*/
List<Log> selectAllByTable(String date);
}<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.rainbowsea.mybatis.mapper.LogMapper">

<select id="selectAllByTable" resultType="com.rainbowsea.mybatis.pojo.Log">
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>select * from t_log_${date};
</select>

</mapper>https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641968-664381997.png
package com.rainbowsea.test;

import com.rainbowsea.mybatis.mapper.LogMapper;
import com.rainbowsea.mybatis.pojo.Log;
import com.rainbowsea.mybatis.utils.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class LogMapperTest {

@Test
public void testSelectAllByTable() {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>SqlSession sqlSession = SqlSessionUtil.openSession();
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>LogMapper mapper = sqlSession.getMapper(LogMapper.class);
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>List<Log> logs = mapper.selectAllByTable("20220902");
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>logs.forEach(log -> {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>System.out.println(log);
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>});
}
}使用 ${} 拼接上的结果为：select * from t_log_20220902; 直接就是 20220902 的值，没有加单引号/双引号。
使用 #{ } 的方式是会带上 ‘’ 单引号的。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642069-1811538983.png
使用 #{} 拼接上的结果为：select * from t_log_‘20220902’; 加上的单引号后拼接上去，t_log_20220902是一个数据表名的，加了单引号后，MySQL 就找不到该数据表了，编译无法通过了。
3.1.2 批量删除

业务背景：一次删除多条记录。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642067-1252099767.png
批量删除：一次删除多条记录
批量删除的SQL语句有两种写法：
第一种：or: delete form t_car where id =1 or id = 2 or id = 3
第二种：delete from t_car where id in(1,2,3)假设如今使用in的方式处置惩罚，前端传过来的字符串：1, 2, 3
如果使用mybatis处置惩罚，应该使用#{} 还是 ${}
使用#{} ：delete from t_user where id in('1,2,3')会加上单引号，实行错误：1292 - Truncated incorrect DOUBLE value: '1,2,3'
使用${} ：delete from t_user where id in(1, 2, 3)，实行乐成
以是我们要接纳 ${} ，不加单引号的形式。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642081-1903515652.png
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642076-752297923.png
package com.rainbowsea.mybatis.mapper;

import com.rainbowsea.mybatis.pojo.Car;

import java.util.List;

/**
* 封装汽车相关信息的pojo类，普通的Java类
*/
public interface CarMapper {

/**
* 批量删除，根据id
* @param ids
* @return
*/
int deleteBath(String ids);
}<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.rainbowsea.mybatis.mapper.CarMapper">

<delete id="deleteBath">
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>delete from t_car where id in(${ids})
</delete>

</mapper>Java步伐测试，
留意因为我们这里是对数据表进行的修改操纵的，以是需要提交一下数据给数据库。
这里我们删除 id为(121，122，123) 三条记录。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642048-63367701.png
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642067-1455974900.png
package com.rainbowsea.test;

import com.rainbowsea.mybatis.mapper.CarMapper;
import com.rainbowsea.mybatis.pojo.Car;
import com.rainbowsea.mybatis.utils.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class TestCarMapper {

@Test
public void testDeleteBath() {
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>SqlSession sqlSession = SqlSessionUtil.openSession();
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>CarMapper mapper = sqlSession.getMapper(CarMapper.class);
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>int count = mapper.deleteBath("121,122,123");
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>sqlSession.commit();
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>sqlSession.close();

}

}如果使用 #{} 是将使用#{} ：delete from t_user where id in('121,122,123')会加上单引号，实行错误：1292 - Truncated incorrect DOUBLE value: '121,122,123'
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642097-205170826.png
3.1.3 模糊查询

需求：查询小米系列的汽车。【只要品牌brand中含有小米两个字的都查询出来。】
关于模糊查询有四种方案：

[*]方案一：'%${brand}%'
[*]方案二: concat('%','${brand}','%')
[*]方案三: count函数，这个是mysql数据库当中的一个函数，专门进行字符串拼接的concat('%',#{brand},'%')
[*]方案四: "%"#{brand}"%", 这种方式比力常用，也避免了SQL注入的问题。
方案一：'%${brand}%'
方案二: concat('%','${brand}','%')
方案三: count函数，这个是mysql数据库当中的一个函数，专门进行字符串拼接的
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>concat('%',#{brand},'%')
方案四: "%"#{brand}"%"四种方式：总的来说，都是为了拼接成字符串，把不是字符串的想办法拼接成字符串。
3.1.3.1 使用 ${ }的方式

方案一：'%${brand}%'
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641998-1359773240.png
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642077-1911086579.png
package com.rainbowsea.mybatis.mapper;

import com.rainbowsea.mybatis.pojo.Car;

import java.util.List;

/**
* 封装汽车相关信息的pojo类，普通的Java类
*/
public interface CarMapper {

/**
* 根据汽车品牌进行模糊查询
* @param brand
* @return
*/
List<Car> selectByBrandLike(String brand);

}<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.rainbowsea.mybatis.mapper.CarMapper">

<select id="selectByBrandLike" resultType="com.rainbowsea.mybatis.pojo.Car">
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>select
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>id,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>car_num as carNum,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>brand,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>guide_price as guidePrice,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>produce_time as produceTime,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>car_type as carType
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>from t_car
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>where brand like '%${brand}%'
</select>

</mapper>Java步伐运行结果：
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641905-408773776.png
方案二: concat('%','${brand}','%')
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641998-128228425.png
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.rainbowsea.mybatis.mapper.CarMapper">

<select id="selectByBrandLike" resultType="com.rainbowsea.mybatis.pojo.Car">
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>select
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>id,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>car_num as carNum,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>brand,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>guide_price as guidePrice,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>produce_time as produceTime,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>car_type as carType
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>from t_car
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>where brand like concat('%','${brand}','%')
</select>
</mapper>https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641996-276812475.png
3.1.3.2 使用 #{ } 的方式

方案三： count函数，这个是mysql数据库当中的一个函数，专门进行字符串拼接的 concat('%',#{brand},'%')
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642067-993251837.png
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.rainbowsea.mybatis.mapper.CarMapper">

<select id="selectByBrandLike" resultType="com.rainbowsea.mybatis.pojo.Car">
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>select
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>id,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>car_num as carNum,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>brand,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>guide_price as guidePrice,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>produce_time as produceTime,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>car_type as carType
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>from t_car
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>where brand like concat('%',#{brand},'%')
</select>
</mapper>https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642075-278622383.png
方案四:"%"#{brand}"%", 这种方式比力常用，也避免了SQL注入的问题。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641999-740996721.png
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.rainbowsea.mybatis.mapper.CarMapper">

<select id="selectByBrandLike" resultType="com.rainbowsea.mybatis.pojo.Car">
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>select
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>id,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>car_num as carNum,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>brand,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>guide_price as guidePrice,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>produce_time as produceTime,
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>car_type as carType
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>from t_car
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>where brand like "%"#{brand}"%"
</select>
</mapper>测试运行：
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642113-1579853876.png
4. typeAliases 别名定义的使用

我们来观察一下CarMapper.xml中的配置信息：
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641910-1356528258.png
resultType 属性用来指定查询结果集的封装类型，这个名字太长，可以起别名吗？可以。
在 mybatis-config.xml文件中使用 typeAliases 标签来起别名，包罗两种方式：
4.1 typeAliases 的第一种方式：typeAlias

https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641978-1161774326.png

<typeAliases>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><typeAlias type="com.rainbowsea.mybatis.pojo.Car" alias="Car"></typeAlias>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><typeAlias type="com.rainbowsea.mybatis.pojo.Log" alias="Log"></typeAlias>
</typeAliases><?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

<typeAliases>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><package name="com.rainbowsea.mybatis.pojo"/>
</typeAliases>
<environments default="mybatis">

<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><environment id="mybatis">
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><transactionManager type="JDBC"/>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><dataSource type="POOLED">
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> <property name="username" value="root"/>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> <property name="password" value="MySQL123"/>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers></dataSource>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers></environment>
</environments>
<mappers>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mapper resource="CarMapper.xml"></mapper>
</mappers>
</configuration><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>

[*]首先要留意typeAliases标签的放置位置，如果不清楚的话，可以看看错误提示信息。
[*]typeAliases标签中的typeAlias可以写多个。
[*]typeAlias：
[*]

[*]type属性：指定给哪个类起别名
[*]alias属性：别名。

[*]

[*]

[*]alias属性不是必须的，如果缺省的话，type属性指定的类型名的简类名作为别名。
[*]alias是大小写不敏感的。也就是说假设alias="Car"，再用的时候，可以CAR，也可以car，也可以Car，都行、

[*]
[*]

留意：接口，一定要为全限定类名(带有包名)，不可以用别名机制
测试：
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642079-1888529705.png
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642079-836049475.png
特殊的：省略 alias 属性之后，别名就是类的简名了，比如 :com.rainbowsea.mybatis.pojo.Car 的别名就是 Car/CAR/cAR，不区分大小写的。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642030-1320613416.png

<typeAliases>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><typeAlias type="com.rainbowsea.mybatis.pojo.Car" alias="Car"></typeAlias>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><typeAlias type="com.rainbowsea.mybatis.pojo.Log" alias="Log"></typeAlias>
</typeAliases> 4.2 typeAliases 的第二种方式：package

如果一个包下的类太多，每个类都要起别名，会导致 typeAlias 标签配置较多，以是mybatis用提供package的配置方式，只需要指定包名，该包下的所有类都自动起别名，别名就是简类名。而且别名不区分大小写。
留意：接口，一定要为全限定类名(带有包名)，不可以用别名机制
这种方式是最常用的。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641889-1675323597.png
<typeAliases>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><package name="com.rainbowsea.mybatis.pojo"/>
</typeAliases>测试：
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642074-1706561320.png
留意：
使用 <?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="">

</mapper>还可以将这个包下的所有的类的全部自动起别名，别名就是简名，不区分大小写
,所有的别名不区分大小写。但是：namespace 不能使用别名机制
同时需要按照一定的顺序放置，放到指定的顺序当中去
5. mappers 路径设置的使用

SQL映射文件的配置方式包罗四种：

[*]resource：从类路径中加载
[*]url：从指定的全限定资源路径中加载
[*]class：使用映射器接口实现类的完全限定类名
[*]package：将包内的映射器接口实现全部注册为映射器
5.1 mapper 标签下的 resource 属性的使用

这种方式是从类路径中加载配置文件，以是这种方式要求SQL映射文件必须放在resources目录下或其子目录下。
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642032-562650847.png
5.2 mapper 标签下的 url 属性的使用

这种方式是一种绝对路径的方式，这种方式不要求配置文件必须放到类的路径当中，哪里都行，只要提供了一个绝对路径就行，这种方式使用少少，因为移植性太差了（并不是以是的系统都有盘符的说法的）。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642032-230387376.png
**需要留意的是：要三个\\\ ，才表现两个 \\ **
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>5.3 mapper 标签下的 class 属性的使用

Class: 这位置提供的是 mapper 接口的全限定接口名，必须带有包名（就是要一定要和对应接口的路径是一致的，一致的，一致的）
如果使用这种方式必须满足以下条件：

[*]SQL映射文件和mapper接口放在同一个目录下。
[*]SQL映射文件的名字也必须和mapper接口名一致。
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> 如果你class指定是:com.rainbowsea.mybatis.mapper.CarMapper<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>那么mybatis框架会自动去com/rainbowsea/mybatis/mapper/CarMapper/的目录下找，留意是 / 留意：也就是说，如果你接纳这种方式，那么你必须包管:CarMapper.xml文件和CarMapper接口必须在同一个目录下，而且名字也是一致的CarMapper接口——》CarMapper.xmlLogMapper接口——> LogMapper.xml提示：
在IDEA的resources 目录下新建多重目录的话，必须是如许创建:
com/rianbowsea/mybatis/mapper/
不然是
com.rianbowsea.mybatis.mapper 这是建包了
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641957-1731570018.png
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642040-2016462680.png
保持一致的同时，名称也要是一致的
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641879-1713224918.png

<typeAliases>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><typeAlias type="com.rainbowsea.mybatis.pojo.Car" alias="Car"></typeAlias>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><typeAlias type="com.rainbowsea.mybatis.pojo.Log" alias="Log"></typeAlias>
</typeAliases>测试运行：
运行步伐：正常！！！
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642037-320505966.png
5.4 package 标签的使用

如果class较多，可以使用这种package的方式，但前提条件和上一种（mapper 标签下的class 属性的使用）方式一样。
如果使用这种方式必须满足以下条件：

[*]SQL映射文件和mapper接口放在同一个目录下。
[*]SQL映射文件的名字也必须和mapper接口名一致。
这种方式是最常用的。
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642048-1528096408.png
运行测试：
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642027-1377574108.png
6. 在 IDEA 中自定义配置文件模板

mybatis-config.xml 和 SqlMapper.xml ，logback 文件可以在IDEA中提前创建好模板，以后通过模板创建配置文件。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642078-1394917695.png
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642028-46493808.png
mybatis 核心配置文件的模板内容：
<?xml version="1.0" encoding="UTF-8"?>

<configuration debug="false">

<appender name="STDOUT" >
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><encoder >
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{50} - %msg%n</pattern>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers></encoder>
</appender>

<logger name="com.apache.ibatis" level="TRACE"/>
<logger name="java.sql.Connection" level="DEBUG"/>
<logger name="java.sql.Statement" level="DEBUG"/>
<logger name="java.sql.PreparedStatement" level="DEBUG"/>

<root level="DEBUG">
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><appender-ref ref="STDOUT"/>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><appender-ref ref="FILE"/>
</root>

</configuration>logback 的日记配置模板内容：
<?xml version="1.0" encoding="UTF-8"?>

<configuration debug="false">

<appender name="STDOUT" >
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><encoder >
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{50} - %msg%n</pattern>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers></encoder>
</appender>

<logger name="com.apache.ibatis" level="TRACE"/>
<logger name="java.sql.Connection" level="DEBUG"/>
<logger name="java.sql.Statement" level="DEBUG"/>
<logger name="java.sql.PreparedStatement" level="DEBUG"/>

<root level="DEBUG">
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><appender-ref ref="STDOUT"/>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><appender-ref ref="FILE"/>
</root>

</configuration>SqLMapper的配置模板内容：
<?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="">

</mapper>7. 补充：插入数据时获取自动天生的主键的值

**前提是：主键是自动天生的。 **
业务背景：一个用户有多个角色。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642056-1692025469.png
插入一条新的记录之后，自动天生了主键，而这个主键需要在其他表中使用时。
插入一个用户数据的同时需要给该用户分副角色：需要将天生的用户的id插入到角色表的user_id字段上。
第一种方式：可以先插入用户数据，再写一条查询语句获取id，然后再插入user_id字段。【比力麻烦】
第二种方式：mybatis提供了一种方式更加便捷。
<?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="">

</mapper><?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="">

</mapper><?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="">

</mapper>insert into t_car values(null,#{carNum},#{brand},#{guidePrice},#{produceTime},#{carType})<?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="">

</mapper>userGeneratedKeys = "true"使用自动天生的主键值，false 则是不使用自动天生的主键值了
keyProperty="id" 指定主键值赋值给POJO类(ORM映射)对象的哪个属性，这个就表现将主键值给Car对象的 id属性。
留意：这个 keyProperty 指定的值，一定要和对应上的 pojo 对象类上的属性一致，不然，不可的。
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642016-1161590039.png
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642141-1222062606.png
package com.rainbowsea.mybatis.mapper;

import com.rainbowsea.mybatis.pojo.Car;

import java.util.List;

/**
* 封装汽车相关信息的pojo类，普通的Java类
*/
public interface CarMapper {

/**
* 插入 Car 信息，并且使用生成的主键值
* @param car
* @return
*/
int insertCarUserGeneratedKey(Car car);

}<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers> insert into t_car<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>values (null, #{carNum}, #{brand}, #{guidePrice}, #{produceTime}, #{carType}) 运行测试：
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642103-1815517555.png
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150642075-1813123113.png
8. 总结：

[*]{ } 与 ${ } 的区别和使用
- #{ } ：先编译 SQL 语句，再对占位符传值，底层是 PrepareedStatement 实现，可以防止 SQL 注入，比较常用
- ${ }：先进行SQL语句的拼接，然后再对SQL语句进行编译，底层是 Statement 实现，这种方式存在 SQL注入现象，SQL注入的风险，简单的说就是，直接将传入的值拼接为了SQL语句，然后再执行的）。只有在需要进行SQL语句关键字拼接的情况下才会用到。
- 简单的说一个区别就是：#{} 传的值是带有 '' 单引号的，而 ${} 传的值是（直接就是值，没有单引号，或者是双引号，两个都没有）
[*]什么情况下必须使用 $
拼接表名
批量删除
模糊查询
[*]typeAliases 别名定义的使用，留意：接口，一定要为全限定类名(带有包名)，不可以用别名机制，发起接纳第二种 package 方式，，同时留意：typeAliases 的正确顺序和位置，可以参考报错信息，进行修正。
<typeAliases>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>
<mappers>
<mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
<mapper resource="org/mybatis/builder/BlogMapper.xml"/>
<mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers><package name="com.rainbowsea.mybatis.pojo"/>
</typeAliases>
[*]mappers 路径设置的使用，发起接纳 package 标签的方式，留意条件，两个条件的一致性。
- SQL映射文件和mapper接口放在同一个目录下。
- SQL映射文件的名字也必须和mapper接口名一致。
[*]在 IDEA 中自定义配置文件模板
[*]插入数据时获取自动天生的主键的值，**前提是：在对应数据表中的主键是自动天生的(自增的方式才行)。 **
<?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="">

</mapper><?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="">

</mapper><?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="">

</mapper>insert into t_car values(null,#{carNum},#{brand},#{guidePrice},#{produceTime},#{carType})<?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="">

</mapper>9. 最后：

“在这个最后的篇章中，我要表达我对每一位读者的感激之情。你们的关注和回复是我创作的动力源泉，我从你们身上吸取了无尽的灵感与勇气。我会将你们的鼓励留在心底，继续在其他的领域奋斗。感谢你们，我们总会在某个时候再次相遇。”
https://img2024.cnblogs.com/blog/3084824/202406/3084824-20240602150641968-1664847922.gif

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MyBatis 的在使用上的留意事项及其辨析