Mybatisplus-IService

IService 是 MyBatis-Plus 提供的一个通用 Service 层接口，它封装了常见的 CRUD 操作，包括插入、删除、查询和分页等。通过继承 IService 接口，可以快速实现对数据库的基本操作，同时保持代码的简洁性和可维护性。

IService 接口中的方法命名遵循了一定的规范，如 get 用于查询单行，remove 用于删除，list 用于查询集合。

本文详细介绍了 MyBatis-Plus 进行持久化操作的各种方法，包括插入、更新、删除、查询和分页等。

package org.example.IServiceTest;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.conditions.update.UpdateWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import org.example.springbootMybatisplus.Starter;
import org.example.springbootMybatisplus.entity.User;
import org.example.springbootMybatisplus.service.UserService;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;import java.util.*;@RunWith(SpringRunner.class)
@SpringBootTest(classes = {Starter.class})
public class IServiceTest1 {@Autowiredprivate UserService userService;//插入一条记录--save@Testpublic void save(){User user=new User("小x");
//        user.setUsername();boolean save = userService.save(user);System.out.println(save);}/*插入（批量）--saveBatchentityList – 实体对象集合*/@Testpublic void saveBatch(){List<User> users= Arrays.asList(new User("小张"),new User("小李"),new User("小王"));boolean saveBatch = userService.saveBatch(users);System.out.println(saveBatch);}/*插入（批量）--saveBatchentityList – 实体对象集合batchSize – 插入批次数量*/@Testpublic void saveBatch2(){List<User> users=Arrays.asList(new User("小1"),new User("小2"),new User("小3"),new User("小4"),new User("小5"));boolean saveBatch = userService.saveBatch(users, 2);System.out.println(saveBatch);}/*批量修改插入--saveOrUpdateBatchentityList – 实体对象集合*/@Testpublic void saveOrUpdateBatch(){List<User> users=Arrays.asList(new User(6L,"小张张"),new User(7L,"小张张张"),new User(8L,"小张张张张"));boolean saveOrUpdateBatch = userService.saveOrUpdateBatch(users);System.out.println(saveOrUpdateBatch);}/*批量修改插入--saveOrUpdateBatchentityList – 实体对象集合batchSize – 每次的数量*/@Testpublic void saveOrUpdateBatch2(){List<User> users=Arrays.asList(new User(16L,"小11"),new User(17L,"小22"),new User(18L,"小33"));boolean saveOrUpdateBatch = userService.saveOrUpdateBatch(users, 2);System.out.println(saveOrUpdateBatch);}//根据 ID 删除--removeById@Testpublic void removeById(){boolean removeById = userService.removeById(20L);System.out.println(removeById);}//根据 columnMap 条件，删除记录--removeByMap@Testpublic void removeByMap(){Map<String,Object> map=new HashMap<>();map.put("username","小4");boolean removeByMap = userService.removeByMap(map);System.out.println(removeByMap);}//根据 entity 条件，删除记录--remove@Testpublic void remove(){QueryWrapper<User> queryWrapper=new QueryWrapper<>();queryWrapper.eq("username","小张3");boolean remove = userService.remove(queryWrapper);System.out.println(remove);}//删除（根据ID 批量删除）--removeByIds@Testpublic void removeByIds(){List<Long> ids=Arrays.asList(16L,17L);boolean removeByIds = userService.removeByIds(ids);System.out.println(removeByIds);}//根据 ID 选择修改--updateById@Testpublic void updateById(){User users=new User();users.setId(15L);users.setUsername("小xx");boolean updateById = userService.updateById(users);System.out.println(updateById);}//根据 UpdateWrapper 条件，更新记录 需要设置sqlset--update//update UpdateWrapper 形式@Testpublic void update(){UpdateWrapper<User> updateWrapper=new UpdateWrapper<>();updateWrapper.eq("username","小明").set("username","小敏");boolean update = userService.update(updateWrapper);System.out.println(update);}//根据 whereEntity 条件，更新记录--update//update WhereWrapper 形式@Testpublic void update2(){User users=new User();users.setUsername("小张44");QueryWrapper<User> whereWrapper =new QueryWrapper<>();whereWrapper .eq("id",10L);boolean update = userService.update(users, whereWrapper );System.out.println(update);}//根据ID 批量更新--updateBatchById//entityList – 实体对象集合@Testpublic void updateBatchById(){List<User> users=Arrays.asList(new User(4L,"小明"),new User(6L,"张无忌"));boolean updateBatchById = userService.updateBatchById(users);System.out.println(updateBatchById);}/*根据ID 批量更新--updateBatchByIentityList – 实体对象集合batchSize – 更新批次数量*/@Testpublic void updateBatchById2(){List<User> users=Arrays.asList(new User(7L,"张三"),new User(8L,"张朗格"));boolean updateBatchById = userService.updateBatchById(users, 1);System.out.println(updateBatchById);}//根据实体对象的主键来判断是执行插入操作还是更新操作--saveOrUpdate//如果实体对象的主键为空：则认为这是一个新记录，MyBatis-Plus 会执行插入操作。//如果实体对象的主键不为空：则认为这是一个已存在的记录，MyBatis-Plus 会根据主键查找对应的记录并执行更新操作。@Testpublic void saveOrUpdate(){User users1=new User();users1.setId(18L);users1.setUsername("小画");//数据库里面有18，这里就是修改User user2=new User();user2.setId(21L);user2.setUsername("张维");//数据库里面没有21，这里就是插入boolean b1 = userService.saveOrUpdate(users1);boolean b2 = userService.saveOrUpdate(user2);System.out.println(b1);System.out.println(b2);}//根据id查询--getById@Testpublic void getById(){User byId = userService.getById(1L);System.out.println(byId);}//查询（根据ID 批量查询）--listByIds@Testpublic void listByIds(){List<Long> ids=Arrays.asList(1L,2L,3L,4L);List<User> userList = userService.listByIds(ids);userList.forEach(System.out::println);}//查询（根据 columnMap 条件）--listByMap@Testpublic void listByMap(){Map<String,Object> columnMap=new HashMap<>();columnMap.put("username","小敏");List<User> listByMap = userService.listByMap(columnMap);listByMap.forEach(System.out::println);}//根据 Wrapper，查询一条记录--getOne//结果集，如果是多个会抛出异常，随机取一条加上限制条件 wrapper.last("LIMIT 1")@Testpublic void getOne(){QueryWrapper<User> queryWrapper=new QueryWrapper<>();queryWrapper.eq("username","zhangsan");User one = userService.getOne(queryWrapper);System.out.println(one);}//根据 Wrapper，查询一条记录--getOne//有多个 result 是否抛出异常@Testpublic void getOne2(){QueryWrapper<User> queryWrapper=new QueryWrapper<>();queryWrapper.eq("username","小敏");User one = userService.getOne(queryWrapper, false);//不抛出异常System.out.println(one);}//根据 Wrapper，查询一条记录--getMap@Testpublic void getMap(){QueryWrapper<User> queryWrapper=new QueryWrapper<>();queryWrapper.eq("username","小敏");Map<String, Object> map = userService.getMap(queryWrapper);System.out.println(map);}//根据 Wrapper，查询一条记录--getObj@Testpublic void getObj(){QueryWrapper<User> queryWrapper=new QueryWrapper<>();queryWrapper.eq("username","小王");Object name = userService.getObj(queryWrapper, obj ->obj);System.out.println(name);}//查询总记录数--count@Testpublic void count() {int count = userService.count();System.out.println(count);}//查询总记录数--count@Testpublic void count2(){QueryWrapper<User> queryWrapper=new QueryWrapper<>();queryWrapper.gt("age",23);int count = userService.count(queryWrapper);System.out.println(count);}//查询列表@Testpublic void list(){QueryWrapper<User> queryWrapper=new QueryWrapper<>();queryWrapper.gt("age",15);List<User> users = userService.list(queryWrapper);users.forEach(System.out::println);}//查询所有@Testpublic void list2(){List<User> users = userService.list();users.forEach(System.out::println);}//翻页查询--page@Testpublic void page1(){IPage<User> page=new Page<>(1,10);QueryWrapper<User> queryWrapper=new QueryWrapper<>();queryWrapper.gt("age",20);IPage<User> userIPage=userService.page(page,queryWrapper);List<User> userList=userIPage.getRecords();long total = userIPage.getTotal();System.out.println("年龄大于20的有："+total);userList.forEach(System.out::println);}//无条件翻页查询--page@Testpublic void page2(){IPage<User> page=new Page<>(1,10);IPage<User> userIPage=userService.page(page);List<User> userList=userIPage.getRecords();long total = userIPage.getTotal();System.out.println("总用户："+total);userList.forEach(System.out::println);}//查询列表--listMaps//listMaps QueryWrapper 形式--设置查询条件为 age > 17，并将结果映射为 Map@Testpublic void listMaps(){QueryWrapper<User> queryWrapper=new QueryWrapper<>();queryWrapper.gt("age",17);List<Map<String, Object>> maps = userService.listMaps(queryWrapper);maps.forEach(System.out::println);}//查询所有列表--listMaps@Testpublic void listMaps2(){List<Map<String, Object>> maps = userService.listMaps();maps.forEach(System.out::println);}//查询全部记录@Testpublic void listObjs(){List<Object> userNames=userService.listObjs(obj-> obj);for (Object userName : userNames) {System.out.println(userName);}}@Testpublic void listObjs2(){QueryWrapper<User> queryWrapper=new QueryWrapper<>();queryWrapper.gt("age",26);List<Object> userNames = userService.listObjs(queryWrapper, obj -> obj);for (Object userName : userNames) {System.out.println(userName);}}//翻页查询--pageMaps@Testpublic void pageMaps(){IPage<Map<String,Object>> page=new Page<>(1,10);QueryWrapper<User> queryWrapper=new QueryWrapper<>();queryWrapper.gt("age",20);IPage<Map<String,Object>> userPageMaps=userService.pageMaps(page,queryWrapper);List<Map<String,Object>> userMapList=userPageMaps.getRecords();long total = userPageMaps.getTotal();System.out.println(total);for (Map<String, Object> userMap : userMapList) {System.out.println(userMap);}}//无条件翻页查询--pageMaps@Testpublic void pageMaps2(){IPage<Map<String,Object>> page=new Page<>(1,10);IPage<Map<String,Object>> userPageMaps=userService.pageMaps(page);List<Map<String,Object>> userMapList=userPageMaps.getRecords();long total = userPageMaps.getTotal();System.out.println(total);for (Map<String, Object> userMap : userMapList) {System.out.println(userMap);}}}