Mybatis中输入输出映射与动态Sql图文详解

package cn.mybatis.po;

public class UserPoJo extends User{
 private User user;

 public void setUser(User user) {
 this.user = user;
 }

 public User getUser() {
 return user;
 }
}

UserPOJO

package cn.mybatis.po;

public class UserVo {
 private UserPoJo userPoJo;

 public UserPoJo getUserPoJo() {
 return userPoJo;
 }

 public void setUserPoJo(UserPoJo userPoJo) {
 this.userPoJo = userPoJo;
 }
}

UserVo

//测试包装类型的查询
 public List<UserPoJo> findUserList(UserVo userVo) throws Exception;

@Test
 public void testFindUserList() throws Exception {
 SqlSession sqlSession = sqlSessionFactory.openSession();
 UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

 UserPoJo userPoJo = new UserPoJo();
 UserVo userVo = new UserVo();
 userPoJo.setSex("男");
 userPoJo.setUsername("u");
 userVo.setUserPoJo(userPoJo);

 List<UserPoJo> userPoJoList = userMapper.findUserList(userVo);

 System.out.println(userPoJoList);
 }

SELECT COUNT(*) FROM t_user

SELECT username FROM t_user WHERE id = 2

<?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="cn.mybatis.mapper.UserMapper">

 <!--定义resultMap
 type:resultMap最终映射的Java对象类型
 id:对resultMap的标识
 -->
 <resultMap id="userResultMap" type="user">
 <!--id:标识查询结果集中的唯一标识-->
 <id column="_id" property="id"></id>
 <!--result:标识查询结果集中其他列的标识-->
 <result column="_username" property="username"></result>
 <result column="_password" property="password"></result>
 <result column="_sex" property="sex"></result>
 <result column="_address" property="address"></result>
 </resultMap>

 <select id="findUserById_resultMap" parameterType="int" resultMap="userResultMap">
 SELECT id _id, username _username, PASSWORD _password, address _address, sex _sex FROM t_user WHERE id = #{id}
 </select>
</mapper>

 //测试resultMap
 public User findUserById_resultMap(int id) throws Exception;

@Test
 public void testFindUserById_resultMap() throws Exception {
 SqlSession sqlSession = sqlSessionFactory.openSession();
 UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

 User user = userMapper.findUserById_resultMap(2);

 System.out.println(user);
 }

<select id="findUserList" parameterType="cn.mybatis.po.UserVo" resultType="cn.mybatis.po.UserPoJo">
 SELECT * FROM t_user
 <where>
  <if test="userPoJo != null">
  <if test="userPoJo.sex != null and userPoJo.sex != ''">
   AND sex = #{userPoJo.sex}
  </if>
  <if test="userPoJo.username != null and userPoJo.username != ''">
   AND username LIKE '%${userPoJo.username}%'
  </if>
  </if>
 </where>
 </select>

<!--定义Sql片段-->
 <sql id="query_user_info">
 <if test="userPoJo != null">
  <if test="userPoJo.sex != null and userPoJo.sex != ''">
  AND sex = #{userPoJo.sex}
  </if>
  <if test="userPoJo.username != null and userPoJo.username != ''">
  AND username LIKE '%${userPoJo.username}%'
  </if>
 </if>
 </sql>

<select id="findUserList" parameterType="cn.mybatis.po.UserVo" resultType="cn.mybatis.po.UserPoJo">
 SELECT * FROM t_user
 <where>
  <include refid="query_user_info"></include>
 </where>
 </select>

<sql id="query_ids">
 <if test="ids != null">
  <!--
  SELECT * FROM t_user WHERE 1=1 AND (id = 1 OR id =2 OR id = 3)
  cilleation: 指定的是输入参数集合的属性名
  item:每次遍历的名称
  open:开始遍历时拼接串
  close:结束遍历时候拼接的串
  separator:遍历的两个对象中间需要拼接的串
  -->
  <foreach collection="ids" item="item_id" open="AND (" close=")" separator=" OR ">
  id=#{item_id}
  </foreach>
 </if>
 </sql>

 <select id="findUserByIds" parameterType="userVo" resultType="userPoJo">
 SELECT * FROM t_user
 <where>
  <include refid="query_ids"></include>
 </where>
 </select>