Mybatis学习5标签：if，where，sql，foreach

包装类：QueryVO.java

package pojo;

import java.util.ArrayList;
import java.util.List;

public class QueryVO {
    
    private User user;
    
    private List<Integer> ids;
    

    public List<Integer> getIds() {
        return ids;
    }

    public void setIds(List<Integer> ids) {
        this.ids = ids;
    }

    public User getUser() {
        return user;
    }

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

mapper.xml

<?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">
<!-- namespace命名空间，隔离sql文件 -->
<!-- #{}占位符相当于jdbc的？ -->
<!-- ${value} 字符串拼接 -->
<!-- 动态代理开发原则
1、namespace必须是接口的全路径
2、接口的方法必须与sql的id一致
3、接口的入参与parameterType类型一致
4、接口的返回值必须与resultType类型一致
 -->
<mapper namespace="mapper.UserMapper">
<!-- sql片段 -->
    <sql id="user_sql">
        id, username,birthday,sex,address
    </sql>

    <select id="getUserBYId" parameterType="int" resultType="pojo.User">
        select 
            <include refid="user_sql"></include>
         from user where id = #{id}
    </select>
    <select id="getUSerByUserName" parameterType="String" resultType="pojo.User">
        select id, username,birthday,sex,address from user where username like '%${value}%'
    </select>
    <select id="getUSerByqueryVo" parameterType="queryVo" resultType="user">
        select id, username,birthday,sex,address from user where username 
        like '%${user.username}%'
    </select>
    <select id="findUserCount" resultType="Integer">
        select count(1) from user
    </select>
    
    <select id="getUSerByPojo" parameterType="user" resultType="pojo.User">
        select id, username,birthday,sex,address from user
        <!--自动补上where关键字 处理多余的and 有where标签就不使用where  -->
        <where>
         <if test="username !=null and username != ''">
             username like '%${value}%'
         </if>
          <if test="sex !=null and sex != ''">
             and sex like #{sex}
         </if>
         </where>
    </select>
    
    <select id="getUSerByIds" parameterType="queryVo" resultType="pojo.User">
        select 
            <include refid="user_sql"></include>
        from user
        <!--自动补上where关键字 处理多余的and 有where标签就不使用where  -->
        <where>
        <!-- foreach 循环标签 -->
        <!--collection 要遍历的集合  -->
             <foreach collection="ids" open="id IN(" item="uid" separator="," close=")">
                 #{uid}
             </foreach>
         </where>
    </select>
</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">
<!-- namespace命名空间，隔离sql文件 -->
<!-- #{}占位符相当于jdbc的？ -->
<!-- ${value} 字符串拼接 -->
<!-- 动态代理开发原则
1、namespace必须是接口的全路径
2、接口的方法必须与sql的id一致
3、接口的入参与parameterType类型一致
4、接口的返回值必须与resultType类型一致
 -->
<mapper namespace="mapper.UserMapper">
<!-- sql片段 -->
    <sql id="user_sql">
        id, username,birthday,sex,address
    </sql>

    <select id="getUserBYId" parameterType="int" resultType="pojo.User">
        select 
            <include refid="user_sql"></include>
         from user where id = #{id}
    </select>
    <select id="getUSerByUserName" parameterType="String" resultType="pojo.User">
        select id, username,birthday,sex,address from user where username like '%${value}%'
    </select>
    <select id="getUSerByqueryVo" parameterType="queryVo" resultType="user">
        select id, username,birthday,sex,address from user where username 
        like '%${user.username}%'
    </select>
    <select id="findUserCount" resultType="Integer">
        select count(1) from user
    </select>
    
    <select id="getUSerByPojo" parameterType="user" resultType="pojo.User">
        select id, username,birthday,sex,address from user
        <!--自动补上where关键字 处理多余的and 有where标签就不使用where  -->
        <where>
         <if test="username !=null and username != ''">
             username like '%${value}%'
         </if>
          <if test="sex !=null and sex != ''">
             and sex like #{sex}
         </if>
         </where>
    </select>
    
    <select id="getUSerByIds" parameterType="queryVo" resultType="pojo.User">
        select 
            <include refid="user_sql"></include>
        from user
        <!--自动补上where关键字 处理多余的and 有where标签就不使用where  -->
        <where>
        <!-- foreach 循环标签 -->
        <!--collection 要遍历的集合  -->
             <foreach collection="ids" open="id IN(" item="uid" separator="," close=")">
                 #{uid}
             </foreach>
         </where>
    </select>    
</mapper>

 测试

    @Test
    public void getUSerByIds() {
        SqlSession openSession = SqlSessionFactoryUtil.getSqlSessionFactory().openSession();
        //获得接口实现类
          UserMapper mapper = openSession.getMapper(UserMapper.class);
         QueryVO vo = new QueryVO();
        vo.setIds(Arrays.asList(1,2,3,4,5,6));
        List<User> uSerByIds = mapper.getUSerByIds(vo);
        for (User user : uSerByIds) {
            System.out.println(user);
        }
        openSession.close();
    }