MyBatis学习存档——mapper.xml映射文件

Posted 2020-10-17 x≒y

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MyBatis 真正的强大在于映射语句，专注于SQL，功能强大，SQL映射的配置却是相当简单

所以我们来看看映射文件的具体结构

一、xml节点结构

mapper为根节点 - namespace命名空间

cache - 配置给定命名空间的缓存

cache-ref – 从其他命名空间引用缓存配置

resultMap –用来描述数据库结果集和对象的对应关系

sql – 可以重用的SQL块，也可以被其他语句引用

insert – 映射插入语句

update – 映射更新语句

delete – 映射删除语句

select – 映射查询语句

二、各节点作用

此处以MyBatis学习存档（1）——入门中反向生成的UsersMapper.xml和UsersMapper.java为例

<?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.mapper.UsersMapper" >
  <resultMap id="BaseResultMap" type="com.pojo.Users" >
    <id column="id" property="id" jdbcType="INTEGER" />
    <result column="name" property="name" jdbcType="VARCHAR" />
    <result column="password" property="password" jdbcType="VARCHAR" />
  </resultMap>
  <sql id="Base_Column_List" >
    id, name, password
  </sql>
  <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Integer" >
    select 
    <include refid="Base_Column_List" />
    from users
    where id = #{id,jdbcType=INTEGER}
  </select>
  <delete id="deleteByPrimaryKey" parameterType="java.lang.Integer" >
    delete from users
    where id = #{id,jdbcType=INTEGER}
  </delete>
  <insert id="insert" parameterType="com.pojo.Users" >
    insert into users (id, name, password
      )
    values (#{id,jdbcType=INTEGER}, #{name,jdbcType=VARCHAR}, #{password,jdbcType=VARCHAR}
      )
  </insert>
  <insert id="insertSelective" parameterType="com.pojo.Users" >
    insert into users
    <trim prefix="(" suffix=")" suffixOverrides="," >
      <if test="id != null" >
        id,
      </if>
      <if test="name != null" >
        name,
      </if>
      <if test="password != null" >
        password,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides="," >
      <if test="id != null" >
        #{id,jdbcType=INTEGER},
      </if>
      <if test="name != null" >
        #{name,jdbcType=VARCHAR},
      </if>
      <if test="password != null" >
        #{password,jdbcType=VARCHAR},
      </if>
    </trim>
  </insert>
  <update id="updateByPrimaryKeySelective" parameterType="com.pojo.Users" >
    update users
    <set >
      <if test="name != null" >
        name = #{name,jdbcType=VARCHAR},
      </if>
      <if test="password != null" >
        password = #{password,jdbcType=VARCHAR},
      </if>
    </set>
    where id = #{id,jdbcType=INTEGER}
  </update>
  <update id="updateByPrimaryKey" parameterType="com.pojo.Users" >
    update users
    set name = #{name,jdbcType=VARCHAR},
      password = #{password,jdbcType=VARCHAR}
    where id = #{id,jdbcType=INTEGER}
  </update>
</mapper>

UsersMapper.xml

package com.mapper;

import com.pojo.Users;

public interface UsersMapper {
    int deleteByPrimaryKey(Integer id);

    int insert(Users record);

    int insertSelective(Users record);

    Users selectByPrimaryKey(Integer id);

    int updateByPrimaryKeySelective(Users record);

    int updateByPrimaryKey(Users record);
}