mybatis使用foreach遍历list集合或者array数组

骑猪看日落 2024-04-17 19:37 72阅读 0赞

# 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>
    
    	<properties resource="db.properties"></properties>
    	
    	<typeAliases>
    		
    		
    	 	
    	 	<package name="com.mybatis_demo.domain"/>
    	 </typeAliases>
    
      <environments default="development">
      
        <environment id="development">
        
          <transactionManager type="JDBC"/>
          
          <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>
      
      <mappers>
      
       
        
        
        
        
        
       
        <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">
    
    <select id="selectByList" resultType="User">
    	select * from t_user where uid in
    	<foreach collection="list" item="item" open="(" separator="," close=")">
    		#{item}
    	</foreach>
    </select>
    
    <select id="selectByArray" resultType="User">
    	select * from t_user where uid in
    	<foreach collection="array" item="item" open="(" separator="," close=")">
    		#{item}
    	</foreach>
    </select>
    
    <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>
    
    <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 ##