mybatis使用foreach遍历list集合或者array数组方式

一、准备工作

1.db.properties文件（记得修改自己的数据库和用户名、密码）

dataSource.driver=com.mysql.jdbc.Driver
dataSource.url=jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=utf8
dataSource.username=blog
dataSource.password=blog

2.主配置文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
  PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<!--  引入外部配置文件-->
	<properties resource="db.properties"></properties>
	<!-- 别名设置，不设置时引用要使用全包名，设置后可以使用自定义别名，更加简洁 -->
	<typeAliases>
		<!-- 别名设置有两种，一种是一个一个设置，另外一种是设置某个包，默认别名为类名（大小写都可以，建议小写） -->
		<!-- 第一种设置
	 	<typeAlias type="com.mybatis_demo.domain.User" alias="user"/>-->
	 	<!-- 第二种设置，整个包下面的类都进行别名设置，推荐第二种 -->
	 	<package name="com.mybatis_demo.domain"/>
	 </typeAliases>
<!-- 环境模式：development开发模式 work工作模式 -->
  <environments default="development">
  <!-- 环境变量 -->
    <environment id="development">
    <!-- 使用jdbc的事务管理 -->
      <transactionManager type="JDBC"/>
      <!-- 使用连接池 -->
      <dataSource type="POOLED">
        <property name="driver" value="${dataSource.driver}"/>
        <property name="url" value="${dataSource.url}"/>
        <property name="username" value="${dataSource.username}"/>
        <property name="password" value="${dataSource.password}"/>
      </dataSource>
    </environment>
  </environments>
  <!-- 引入mapper映射文件 -->
  <mappers>
  <!--  1.相对路径引入-->
   <!--  <mapper resource="mapper/UserMapper.xml"/> -->
    <!-- 2.绝对路径引入 -->
    <!-- <mapper url="file:\\\D:\sts-bundle\workplace\mybatis_demo\src\main\resources\mapper\UserMapper.xml"/> -->
    <!-- 3.对应mapper接口全包名引入，需要对应的mapper.xml与接口mapper处于同一包下才可以，且xml文件名与接口名要相同，xml文件中的namespace必须是对应接口的全包名 -->
    <!-- <mapper class="com.mybatis_demo.mapper.UserMapper"/> -->
    <!-- 4.包引入，要求跟接口引入一样 -->
   <!--  <mapper resource="mapper/UserMapper2.xml"/> -->
    <package name="com.mybatis_demo.mapper"/>
  </mappers>
</configuration>

3.创建User类和包装类UserVo

User.java

package com.mybatis_demo.domain;
public class User {
	private Integer uid;
	private String uname;
	private Integer age;
	private String address;
	public Integer getUid() {
		return uid;
	}
	public void setUid(Integer uid) {
		this.uid = uid;
	}
	public String getUname() {
		return uname;
	}
	public void setUname(String uname) {
		this.uname = uname;
	}
	public Integer getAge() {
		return age;
	}
	public void setAge(Integer age) {
		this.age = age;
	}
	public String getAddress() {
		return address;
	}
	public void setAddress(String address) {
		this.address = address;
	}
	@Override
	public String toString() {
		return "User [uid=" + uid + ", uname=" + uname + ", age=" + age + ", address=" + address + "]";
	}
}

UserVo.java

package com.mybatis_demo.domain;
import java.util.List;
public class UserVo extends User {
	private Integer[] ids;
	private List<Integer> idList;
	public Integer[] getIds() {
		return ids;
	}
	public void setIds(Integer[] ids) {
		this.ids = ids;
	}
	public List<Integer> getIdList() {
		return idList;
	}
	public void setIdList(List<Integer> idList) {
		this.idList = idList;
	}

}

二、遍历数组和集合的映射文件和对应的接口

1.mapper映射文件

<?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.mybatis_demo.mapper.UserMapper">
<!-- 遍历list集合，collection="list"，如果你传参的时候是直接传递list集合，那么这里只能填list,不能填参数名 -->
<select id="selectByList" resultType="User">
	select * from t_user where uid in
	<foreach collection="list" item="item" open="(" separator="," close=")">
		#{item}
	</foreach>
</select>
<!-- 遍历数组 ，collection="array"，如果你传参的时候是直接传递数组，那么这里只能填array,不能填参数名-->
<select id="selectByArray" resultType="User">
	select * from t_user where uid in
	<foreach collection="array" item="item" open="(" separator="," close=")">
		#{item}
	</foreach>
</select>
<!-- 遍历包装类中的数组，collection="ids"，这里不再是array,而是包装类中对应的变量名，因为你传递的参数是一个包装类，mybatis是通过get方法获取包装类中的数组 -->
<select id="selectUserVoByArray" parameterType="UserVo" resultType="User">
	select * from t_user where uid in
	<foreach collection="ids" item="item" open="(" separator="," close=")">
		#{item}
	</foreach>
</select>
<!-- 遍历包装类中的list集合，collection="idList"，这里不再是list,而是包装类中对应的变量名，因为你传递的参数是一个包装类，mybatis是通过get方法获取包装类中的list集合 -->
<select id="selectUserVoByList" parameterType="UserVo" resultType="User">
	select * from t_user where uid in
	<foreach collection="idList" item="item" open="(" separator="," close=")">
		#{item}
	</foreach>
</select>
</mapper>

2.mapper接口

UserMapper.interface

package com.mybatis_demo.mapper;
import java.util.List;
import java.util.Map;
import com.mybatis_demo.domain.User;
import com.mybatis_demo.domain.UserVo;
public interface UserMapper {
	//mybatis使用mapper动态代理

	//4大原则，一个注意
	//1.接口中的方法名需要与对应mapper.xml的id一致
	//2.接口中的返回值需要与对应mapper.xml的返回值类型保持一致
	//3.接口中的参数需要与对应mapper.xml的参数类型、个数、参数名保持一致
	//4.对应mapper.xml的名字空间需要修改成对应接口的全包名
	//注意：mapper动态代理根据返回值类型,mybatis会自动选择调用selectone还是selectlist....
	//用list封装条件
	public List<User> selectByList(List<Integer> testlist);
	//用数组封装条件
	public List<User> selectByArray(Integer[] ids);
	//用包装类中的数组封装条件
	public List<User> selectUserVoByArray(UserVo userVo);
	//用包装类中的list封装条件
	public List<User> selectUserVoByList(UserVo userVo);
}

三、测试代码

package com.mybatis_demo.test;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import com.mybatis_demo.domain.User;
import com.mybatis_demo.domain.UserVo;
import com.mybatis_demo.mapper.UserMapper;
public class TestMapper {

	//用包装类中的list封装条件，传递参数是一个包装类
	@Test
	public void test_selectUserVoByList() {
		try {
			 //读取配置文件
			InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
			//创建SqlSessionFactoryBuilder对象，用来获取SqlSessionFactory对象
			SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
			//利用SqlSessionFactoryBuilder对象build一个SqlSessionFactory对象
			SqlSessionFactory build = builder.build(in);
			//利用sqlSessionFactory获取session对象
			SqlSession session = build.openSession();
			//通过session对象获取对应mapper接口
			UserMapper mapper = session.getMapper(UserMapper.class);
			List<Integer> idList = new ArrayList<Integer>();
			idList.add(5);
			idList.add(3);
			idList.add(123);
			idList.add(19);
			UserVo userVo = new UserVo();
			userVo.setIdList(idList);
			List<User> users = mapper.selectUserVoByList(userVo);
			for (User user : users) {
				System.out.println(user);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	//用包装类中的array封装条件，传递参数是一个包装类
	@Test
	public void test_selectUserVoByArray() {
		try {
			 //读取配置文件
			InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
			//创建SqlSessionFactoryBuilder对象，用来获取SqlSessionFactory对象
			SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
			//利用SqlSessionFactoryBuilder对象build一个SqlSessionFactory对象
			SqlSessionFactory build = builder.build(in);
			//利用sqlSessionFactory获取session对象
			SqlSession session = build.openSession();
			//通过session对象获取对应mapper接口
			UserMapper mapper = session.getMapper(UserMapper.class);
			Integer[] ids = new Integer[]{5,9,30};
			UserVo userVo = new UserVo();
			userVo.setIds(ids);
			List<User> users = mapper.selectUserVoByArray(userVo);
			for (User user : users) {
				System.out.println(user);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	//用数组封装条件，传递参数是一个数组
	@Test
	public void test_selectByArray() {
		try {
			 //读取配置文件
			InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
			//创建SqlSessionFactoryBuilder对象，用来获取SqlSessionFactory对象
			SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
			//利用SqlSessionFactoryBuilder对象build一个SqlSessionFactory对象
			SqlSessionFactory build = builder.build(in);
			//利用sqlSessionFactory获取session对象
			SqlSession session = build.openSession();
			//通过session对象获取对应mapper接口
			UserMapper mapper = session.getMapper(UserMapper.class);
			Integer[] ids = new Integer[]{5,9,30};
			List<User> users = mapper.selectByArray(ids);
			for (User user : users) {
				System.out.println(user);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	//用list封装条件，传递参数是一个list集合
	@Test
	public void test_selectByList() {
		try {
			 //读取配置文件
			InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
			//创建SqlSessionFactoryBuilder对象，用来获取SqlSessionFactory对象
			SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
			//利用SqlSessionFactoryBuilder对象build一个SqlSessionFactory对象
			SqlSessionFactory build = builder.build(in);
			//利用sqlSessionFactory获取session对象
			SqlSession session = build.openSession();
			//通过session对象获取对应mapper接口
			UserMapper mapper = session.getMapper(UserMapper.class);
			List<Integer> list = new ArrayList<Integer>();
			list.add(5);
			list.add(3);
			list.add(123);
			list.add(19);
			List<User> users = mapper.selectByList(list);
			for (User user : users) {
				System.out.println(user);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

四、总结

1.如果你传参的时候直接传一个数组，那么使用foreach遍历时collection=“array”,这里是固定写法，即这里的array与你的实参名无关

2.如果你传参的时候直接传一list集合，那么使用foreach遍历时collection=“list”,这里是固定写法，即这里的list与你的实参名无关

3.如果你传参的时候直接传一个含有数组成员变量的类，那么使用foreach遍历时collection=“你的变量名”,这里不再是固定写法，即这里的命名取决于成员变量的变量名，例如：成员变量名是test,那么就是collection=“test”

4.如果你传参的时候直接传一个含有list集合成员变量的类，跟3的情况一样

以上为个人经验，希望能给大家一个参考，也希望大家多多支持我们。