MyBatisX插件

在真正开发过程中对于一些复杂的SQL和多表联查就需要我们自己去编写代码和SQL语句,这个时候可以使用MyBatisX插件帮助我们简化开发

• 安装MyBatisX插件: File -> Settings -> Plugins -> 搜索MyBatisx插件搜索安装然后重启IDEA

跳转文件功能

由于一个项目中的mapper接口和映射文件有很多找起来很麻烦, 而MyBatisX插件可以快速找到mapper接口对应的映射文件以及映射文件对应的mapper接口

在application.xml文件中指定SQL映射文件的位置,mybatis-plus的mapper-locations属性可以指定配置文件的位置(默认从类路径下的mapper目录下加载)

mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  #设置MyBatis-Plus的全局配置
  mapper-locations: SQL映射文件的路径

代码生成功能

第一部: 创建一个Spring Boot工程并引入相关依赖, 在application.yml文件中配置数据源的连接信息

spring:
  # 配置数据源信息
 datasource:
    # 配置数据源类型(Spring boot默认使用的数据源)
    type: com.zaxxer.hikari.HikariDataSource
    # 配置连接数据库的各个信息
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/mybatis_plus?characterEncoding=utf-8&userSSL=false
    username: root
    password: 123456

<dependencies>
    <dependency>
        <!--spring boot的启动器-->
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
        <!--spring boot的测试启动器-->
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <!--mybatis-plus的启动器-->
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.5.1</version>
    </dependency>
    <dependency>
        <!--简化实体类开发的依赖(还需要下载lombok插件)-->
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
    <dependency>
        <!--mysql的驱动,Spring boot默认的是8以上的版本-->
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>
</dependencies>

第二步: 在IDEA的Database中设置参数连接本地的MySQL数据库

第三步: 使用MyBatisX插件设置生成表相关的mapper,service,映射文件的存放位置

查看mapper接口,mapper接口的映射文件,service接口及其实现类的最终生成位置

自定义方法和SQL

根据mapper接口中的自定义的模板方法名在SQL映射文件中生成对应的增删改查的SQL语句,自动将mapper接口中的方法与映射文件的SQL语句相关联

• 自定义增删改查的方法时一般以insert,select,update,delete为前缀

public interface UserMapper extends BaseMapper<User> {
    //添加数据时,如果实体类属性为null则不为该属性对应的字段赋值
    int insertSelective(User user);
    //根据uid和username删除用户
    int deleteByUidAndUserName(@Param("uid") Long uid, @Param("userName") String userName);
    //根据uid更新用户的年龄和性别
    int updateAgeAndSexByUid(@Param("age") Integer age, @Param("sex") Integer sex, @Param("uid") Long uid);
    //查询年龄和性别根据年龄的区间范围
    List<User> selectAgeAndSexByAgeBetween(@Param("beginAge") Integer beginAge, @Param("endAge") Integer endAge);
    //查询所有字段根据年龄降序
    List<User> selectAllOrderByAgeDesc();
}

<?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.atguigu.mybatisx.mapper.UserMapper">
    <resultMap id="BaseResultMap" type="com.atguigu.mybatisx.pojo.User">
        <id property="uid" column="uid" jdbcType="BIGINT"/>
        <result property="userName" column="user_name" jdbcType="VARCHAR"/>
        <result property="age" column="age" jdbcType="INTEGER"/>
        <result property="email" column="email" jdbcType="VARCHAR"/>
        <result property="sex" column="sex" jdbcType="INTEGER"/>
        <result property="isDeleted" column="is_deleted" jdbcType="INTEGER"/>
    </resultMap>
	<!--SQL片段,记录表中的所有字段-->
    <sql id="Base_Column_List">
        uid,user_name,age,email,sex,is_deleted
    </sql>
    <!--int insertSelective(User user);-->
    <insert id="insertSelective">
        insert into t_user
        <trim prefix="(" suffix=")" suffixOverrides=",">
            <if test="uid != null">uid,</if>
            <if test="userName != null">user_name,</if>
            <if test="age != null">age,</if>
            <if test="email != null">email,</if>
            <if test="sex != null">sex,</if>
            <if test="isDeleted != null">is_deleted,</if>
        </trim>
        values
        <trim prefix="(" suffix=")" suffixOverrides=",">
            <if test="uid != null">#{uid,jdbcType=BIGINT},</if>
            <if test="userName != null">#{userName,jdbcType=VARCHAR},</if>
            <if test="age != null">#{age,jdbcType=INTEGER},</if>
            <if test="email != null">#{email,jdbcType=VARCHAR},</if>
            <if test="sex != null">#{sex,jdbcType=INTEGER},</if>
            <if test="isDeleted != null">#{isDeleted,jdbcType=INTEGER},</if>
        </trim>
    </insert>
    <!--int deleteByUidAndUserName(@Param("uid") Long uid, @Param("userName") String userName);-->
    <delete id="deleteByUidAndUserName">
        delete from t_user where uid = #{uid,jdbcType=NUMERIC} AND user_name = #{userName,jdbcType=VARCHAR}
    </delete>
    <!--int updateAgeAndSexByUid(@Param("age") Integer age, @Param("sex") Integer sex, @Param("uid") Long uid);-->
    <update id="updateAgeAndSexByUid">
        update t_user set age = #{age,jdbcType=NUMERIC},sex = #{sex,jdbcType=NUMERIC} where uid = #{uid,jdbcType=NUMERIC}
    </update>
    <!--List<User> selectAgeAndSexByAgeBetween(@Param("beginAge") Integer beginAge, @Param("endAge") Integer endAge);-->
    <select id="selectAgeAndSexByAgeBetween" resultMap="BaseResultMap">
        select age, sex from t_user where age between #{beginAge,jdbcType=INTEGER} and #{endAge,jdbcType=INTEGER}
    </select>
    <!--List<User> selectAllOrderByAgeDesc();-->
    <select id="selectAllOrderByAgeDesc" resultMap="BaseResultMap">
        select <include refid="Base_Column_List"/> from  t_user order by age desc
    </select>
</mapper>