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# Mybatis快速开箱

# 引入依赖

<!-- mybatis依赖 -->
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>3.0.3</version>
</dependency>

<!--jdbc的驱动-->
<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
</dependency>

# 配置文件

以yaml文件为例

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://123.60.138.52:3306/user
    username: adaker
    password: 123456

# 实体类

Java类中的属性要和mysql中的字段一样 建议使用lombok

假设数据库是：
|id     |image      |box1
|-------|-----------|--------|
|1      |xxxxx      |xxxxxx

@Data
public class Image {
    int id;
    String image;
    String box1;
}

# Mapper层 {#Mapper层}

# 注解式

  • @Mapper注解代表这个是一个
  • @Select 查询语句
  • @Insert 插入语句
  • @Update 更新语句
  • @Delete 删除语句
/*
create table Image (
    id int primary key default 0 auto_increment,
    image varchar(100),
    box1 varchar(100)
);
*/
@Mapper
public interface ImageMapper {
    @Select("select * from 'Image' where id = ${id}")
    Image getImage(int id);

    @Insert("insert into 'Image' value (null,'1','1')")
    void addImage(String image, String box1);

    @Update("update 'Image' set image = ${newImage} where id = &{id} ")
    void updateImage(int id,String newImage);

    @Delete("delete from 'Image' where id = ${id}")
    int deleteImage(int id);
}

# 配置文件式

# 修改application配置 {#修改application配置}
mybatis:
    # 指定主配置文件路径
    config-location: classpath:/mybatis/mybatis-config.xml
    # 指定映射文件路径
    mapper-locations: classpath:/mybatis/mapper/*.xml
# classpath -> src/main/resources
# 添加MyBatis配置文件 {#添加Mybatis配置文件}
  • mybatis-config.xml
  • mapper文件

全局配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!--全局配置文件-->
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

</configuration>

mapper文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.testpaperrgb.Mapper.ImageMapper">
    <select id="getImage" resultType="com.example.testpaperrgb.Entity.Image">
        SELECT * FROM Image WHERE id = #{id}
    </select>
</mapper>
# 编写接口 {#编写接口}
@Mapper
public interface ImageMapper {
//    @Select("select * from Image")
    Image getImage(int id);
}

# 配置文件知识点

# yaml文件配置

用于配置Mybatis的额外功能

mybatis:
  configuration:
    map-underscore-to-camel-case: true # 开启下划线转驼峰
  config-location: classpath:/mybatis-config.xml # 全局配置路径
  mapper-locations: classpath:/mapper/*.xml # Mapper文件路径

# configuration文件配置

用于配置Mybatis的全局文件 有顺序要求

  • typealiases
    • package 设置实体类的根路径
  • mappers
    • resource 设置xml根路径
    • package 设置Mapper类的根路径
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd"> 
<configuration>
    <typeAliases>
        <package name="com.example.testpaperrgb.Entity"/>
    </typeAliases>
    <mappers>
        <package name="com.example.testpaperrgb.Mapper"/>
    </mappers>
</configuration>

# mapper文件配置

用于配置Mapper文件如何映射

  • select
  • insert
  • update
  • delete
  • resultMap
    • result 适合用于Java属性和MySQL字段一致的情况
<?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="ImageMapper">
    <resultMap id="imageMap" type="Image">
        <result property="id" column="id"/>
        <result property="image" column="image"/>
        <result property="box1" column="box1" />
    </resultMap>
    <select id="getImage" resultType="Image">
        SELECT * FROM Image WHERE id = #{id} 
    </select>
</mapper>