foreach标签

最新推荐文章于 2025-05-04 09:07:29 发布

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最新推荐文章于 2025-05-04 09:07:29 发布

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分类专栏： mybatis

本文链接：https://blog.youkuaiyun.com/weixin_43076448/article/details/98648305

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本文详细介绍如何在MyBatis中使用foreach标签实现基于数组或List的批量查询操作，通过具体示例展示如何在userMapper.xml中配置SQL语句，以及在userMapper.java中定义相应的方法，最后提供了一个测试用例的实现。

向sql传递数组或List，mybatis使用foreach解析，如下：

根据多个id查询用户信息

查询sql：SELECT * FROM user WHERE id IN (10,22,24)

1.userMapper.xml

<mapper namespace="cn.itcast.mybatis.mapper.UserMapper">

<sql id="userFild">
select * from user
</sql>
   <select id="selectUserByIds" parameterType="QueryVo" resultType="User">
   
   <include refid="userFild"/>
   <where>
   id in

//方式一
<foreach collection="idsList" item="id" separator="," open="(" close=")">

//方式二

// <foreach collection="array" item="id" separator="," open="(" close=")">

//方式三

// <foreach collection="list" item="id" separator="," open="(" close=")">

   #{id}
   </foreach>
   </where>
   </select>

</mapper>

2.userMapper.java

package cn.itcast.mybatis.mapper;

import java.util.List;

import cn.itcast.mybatis.pojo.QueryVo;
import cn.itcast.mybatis.pojo.User;
public interface UserMapper {
       //根据多个id查询用户信息
       //方式二：List<User> selectUserByIds(Integer[] ids);
       //方式三：List<User> selectUserByIds(List<Integer> idsList);

//方式一
List<User> selectUserByIds(QueryVo vo);
}

3.QueryVo.java

package cn.itcast.mybatis.pojo;

import java.util.List;

public class QueryVo {
   // 包含其他的pojo
       private User user;
       List<Integer> idsList;
       Integer[] ids;
       public User getUser() {
           return user;
       }
       public void setUser(User user) {
           this.user = user;
       }
       public List<Integer> getIdsList() {
           return idsList;
       }
       public void setIdsList(List<Integer> idsList) {
           this.idsList = idsList;
       }
       public Integer[] getIds() {
           return ids;
       }
       public void setIds(Integer[] ids) {
           this.ids = ids;
       }
  }

4.测试：MybatisMapperTest.java

private SqlSessionFactory sqlSessionFactory;

   @Before
   public void init() throws Exception {
       // 创建SqlSessionFactoryBuilder
       SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
       // 加载SqlMapConfig.xml配置文件
       InputStream inputStream = Resources.getResourceAsStream("sqlMapConfig.xml");
       // 创建SqlsessionFactory
       this.sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream);
   }

//根据多个id查询用户信息
   @Test
   public void testselectUserByIds() {
       // mybatis和spring整合，整合之后，交给spring管理
       SqlSession sqlSession = this.sqlSessionFactory.openSession();
       // 创建Mapper接口的动态代理对象，整合之后，交给spring管理
       UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

/*方式二

Integer[] ids = new Integer[3];
       ids[0] = 25;
       ids[2] = 22;
       ids[1] = 24;
       List<User> users = userMapper.selectUserByIds(ids);
*/

//方式一、三
       List<Integer> ids=new ArrayList<>();
       ids.add(10);
       ids.add(22);
       ids.add(24);
       QueryVo vo=new QueryVo();
       vo.setIdsList(ids);
       List<User> users = userMapper.selectUserByIds(vo);
for(User user2:users) {
   System.out.println(user2);
}
   }
}