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mybatis使用foreach遍歷list集合或者array數組方式

瀏覽：11日期：2023-10-18 13:18:47

一、準備工作1.db.properties文件（記得修改自己的數據庫和用戶名、密碼）

dataSource.driver=com.mysql.jdbc.DriverdataSource.url=jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=utf8dataSource.username=blogdataSource.password=blog2.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.創建User類和包裝類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;}@Overridepublic 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、遍歷數組和集合的映射文件和對應的接口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 resultType='User'>select * from t_user where uid in<foreach collection='list' item='item' open='(' separator=',' close=')'>#{item}</foreach></select><select resultType='User'>select * from t_user where uid in<foreach collection='array' item='item' open='(' separator=',' close=')'>#{item}</foreach></select><select parameterType='UserVo' resultType='User'>select * from t_user where uid in<foreach collection='ids' item='item' open='(' separator=',' close=')'>#{item}</foreach></select><select 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動態代理//4大原則，一個注意//1.接口中的方法名需要與對應mapper.xml的id一致//2.接口中的返回值需要與對應mapper.xml的返回值類型保持一致//3.接口中的參數需要與對應mapper.xml的參數類型、個數、參數名保持一致//4.對應mapper.xml的名字空間需要修改成對應接口的全包名//注意：mapper動態代理根據返回值類型,mybatis會自動選擇調用selectone還是selectlist....//用list封裝條件public List<User> selectByList(List<Integer> testlist);//用數組封裝條件public List<User> selectByArray(Integer[] ids);//用包裝類中的數組封裝條件public List<User> selectUserVoByArray(UserVo userVo);//用包裝類中的list封裝條件public List<User> selectUserVoByList(UserVo userVo);}三、測試代碼

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 {//用包裝類中的list封裝條件，傳遞參數是一個包裝類@Testpublic void test_selectUserVoByList() {try { //讀取配置文件InputStream in = Resources.getResourceAsStream('sqlMapConfig.xml');//創建SqlSessionFactoryBuilder對象，用來獲取SqlSessionFactory對象SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();//利用SqlSessionFactoryBuilder對象build一個SqlSessionFactory對象SqlSessionFactory build = builder.build(in);//利用sqlSessionFactory獲取session對象SqlSession session = build.openSession();//通過session對象獲取對應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();}}//用包裝類中的array封裝條件，傳遞參數是一個包裝類@Testpublic void test_selectUserVoByArray() {try { //讀取配置文件InputStream in = Resources.getResourceAsStream('sqlMapConfig.xml');//創建SqlSessionFactoryBuilder對象，用來獲取SqlSessionFactory對象SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();//利用SqlSessionFactoryBuilder對象build一個SqlSessionFactory對象SqlSessionFactory build = builder.build(in);//利用sqlSessionFactory獲取session對象SqlSession session = build.openSession();//通過session對象獲取對應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();}}//用數組封裝條件，傳遞參數是一個數組@Testpublic void test_selectByArray() {try { //讀取配置文件InputStream in = Resources.getResourceAsStream('sqlMapConfig.xml');//創建SqlSessionFactoryBuilder對象，用來獲取SqlSessionFactory對象SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();//利用SqlSessionFactoryBuilder對象build一個SqlSessionFactory對象SqlSessionFactory build = builder.build(in);//利用sqlSessionFactory獲取session對象SqlSession session = build.openSession();//通過session對象獲取對應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封裝條件，傳遞參數是一個list集合@Testpublic void test_selectByList() {try { //讀取配置文件InputStream in = Resources.getResourceAsStream('sqlMapConfig.xml');//創建SqlSessionFactoryBuilder對象，用來獲取SqlSessionFactory對象SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();//利用SqlSessionFactoryBuilder對象build一個SqlSessionFactory對象SqlSessionFactory build = builder.build(in);//利用sqlSessionFactory獲取session對象SqlSession session = build.openSession();//通過session對象獲取對應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、總結

1.如果你傳參的時候直接傳一個數組，那么使用foreach遍歷時collection=“array”,這里是固定寫法，即這里的array與你的實參名無關

2.如果你傳參的時候直接傳一list集合，那么使用foreach遍歷時collection=“list”,這里是固定寫法，即這里的list與你的實參名無關

3.如果你傳參的時候直接傳一個含有數組成員變量的類，那么使用foreach遍歷時collection=“你的變量名”,這里不再是固定寫法，即這里的命名取決于成員變量的變量名，例如：成員變量名是test,那么就是collection=“test”

4.如果你傳參的時候直接傳一個含有list集合成員變量的類，跟3的情況一樣

以上為個人經驗，希望能給大家一個參考，也希望大家多多支持好吧啦網。

Mybatis 數據庫

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