MyBatisPlus-基础CRUD操作

官网参考链接：https://baomidou.com/pages/49cc81/#service-crud-%E6%8E%A5%E5%8F%A3

工程项目续用上一篇:MyBatisPlus入门学习：利用MP代码生成器快速开发

结构图：

在application.yml文件加上日志输出可以打印sql语句

mybatis-plus:configuration:log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

Mapper CRUD 接口

说明:

通用 CRUD 封装BaseMapper接口，为 Mybatis-Plus 启动时自动解析实体表关系映射转换为 Mybatis 内部对象注入容器

泛型 T 为任意实体对象

参数 Serializable 为任意类型主键 Mybatis-Plus 不推荐使用复合主键约定每一张表都有自己的唯一 id 主键

对象 Wrapper 为条件构造器

使用：

在MpDemoApplicationTests添加方法

insert

// 插入一条记录
int insert(T entity);

@Test
void mapperInsert(){Singer singer=new Singer();singer.setName("陶喆");singer.setAge(22);singer.setOther("空无一人 这片沙滩~");int i = singerMapper.insert(singer);System.out.println("i = " + i);
}

注意返回值是int类型，返回的也不是id，返回1代表插入成功

select

// 根据 ID 查询
T selectById(Serializable id);
// 根据 entity 条件，查询一条记录
T selectOne(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);// 查询（根据ID 批量查询）
List<T> selectBatchIds(@Param(Constants.COLLECTION) Collection<? extends Serializable> idList);
// 根据 entity 条件，查询全部记录
List<T> selectList(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
// 查询（根据 columnMap 条件）
List<T> selectByMap(@Param(Constants.COLUMN_MAP) Map<String, Object> columnMap);
// 根据 Wrapper 条件，查询全部记录
List<Map<String, Object>> selectMaps(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
// 根据 Wrapper 条件，查询全部记录。注意： 只返回第一个字段的值
List<Object> selectObjs(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);// 根据 entity 条件，查询全部记录（并翻页）
IPage<T> selectPage(IPage<T> page, @Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
// 根据 Wrapper 条件，查询全部记录（并翻页）
IPage<Map<String, Object>> selectMapsPage(IPage<T> page, @Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
// 根据 Wrapper 条件，查询总记录数
Integer selectCount(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);

参数说明：

测试：

SelectByIdAndBatchIds()

@Test
void mapperSelectByIdAndBatchIds() {String id1 = "1556577794717298690";String id2 = "1556592930551185410";String id3 = "1556593922332053506";List<String> ids= new ArrayList<>();ids.add(id1);ids.add(id2);ids.add(id3);Singer singer = singerMapper.selectById(id1);System.out.println("===================根据单个id查询：\n"+singer.toString());List<Singer> singers = singerMapper.selectBatchIds(ids);System.out.println("===================根据多个id查询：");singers.forEach(System.out::println);
}

控制台输出：

selectOne

@Test
void mapperSelectOne() {QueryWrapper<Singer> wrapper = new QueryWrapper<>();wrapper.eq("age",18);Singer singer = singerMapper.selectOne(wrapper);System.out.println("singer = " + singer.toString());
}

控制台输出：

selcetList

@Test
void mapperSelectList() {List<Singer> singers = singerMapper.selectList(null);singers.forEach(System.out::println);
}

控制台输出：

selectByMap

@Test
void mapperSelectByMap() {Map map=new HashMap<>();map.put("age",18);List<Singer> singers = singerMapper.selectByMap(map);singers.forEach(System.out::println);
}

控制台输出：

selectMaps

@Test
void mapperSelectMaps() {List<Map<String, Object>> maps = singerMapper.selectMaps(null);maps.forEach(System.out::println);
}

控制台输出：

selectObjs

注意：此方法只返回第一个字段的值

@Test
void mapperSelectObjs() {List<Object> objects = singerMapper.selectObjs(null);objects.forEach(System.out::println);
}

控制台输出：

selectPage

@Test
void mapperSelectPage() {IPage<Singer> singerIPage = singerMapper.selectPage(new Page<>(1,10), null);singerIPage.getRecords().forEach(System.out::println);
}

控制台输出：

selectMapsPage

@Test
void mapperSelectMapsPage() {Page<Map<String, Object>> mapPage = singerMapper.selectMapsPage(new Page<>(1, 10), null);mapPage.getRecords().forEach(System.out::println);
}

控制台输出：

selectCount

@Test
void mapperSelectCount() {Long count = singerMapper.selectCount(null);System.out.println("count = " + count);
}

update

// 根据 whereWrapper 条件，更新记录
int update(@Param(Constants.ENTITY) T updateEntity, @Param(Constants.WRAPPER) Wrapper<T> whereWrapper);
// 根据 ID 修改
int updateById(@Param(Constants.ENTITY) T entity);

@Test
void mapperUpdate() {QueryWrapper<Singer> wrapper = new QueryWrapper<>();wrapper.eq("age",17);Singer singer = singerMapper.selectOne(wrapper);System.out.println("singer.toString() = " + singer.toString());singer.setOther("改一下");singerMapper.update(singer,wrapper);System.out.println("=============================update======================================");List<Singer> singers = singerMapper.selectList(null);singers.forEach(System.out::println);
}@Testvoid mapperUpdateById() {QueryWrapper<Singer> wrapper = new QueryWrapper<>();wrapper.eq("age",17);Singer singer = singerMapper.selectOne(wrapper);System.out.println("singer.toString() = " + singer.toString());singer.setOther("改回来");singerMapper.updateById(singer);System.out.println("=============================update======================================");List<Singer> singers = singerMapper.selectList(null);singers.forEach(System.out::println);}

delete

@Test
void mapperDelete(){QueryWrapper<Singer> wrapper = new QueryWrapper<>();wrapper.eq("age",22);singerMapper.delete(wrapper);System.out.println("=============================delete======================================");List<Singer> singers = singerMapper.selectList(null);singers.forEach(System.out::println);
}@Testvoid mapperDeleteBatchsIds(){ArrayList<String> ids = new ArrayList<>();ids.add("1556830638657703938");singerMapper.deleteBatchIds(ids);System.out.println("=============================delete======================================");List<Singer> singers = singerMapper.selectList(null);singers.forEach(System.out::println);}@Testvoid mapperDeleteByMap(){Map<String,Object> map=new HashMap<>();map.put("age",22);singerMapper.deleteByMap(map);System.out.println("=============================delete======================================");List<Singer> singers = singerMapper.selectList(null);singers.forEach(System.out::println);}

Service CRUD接口

说明:

通用 Service CRUD 封装IService 接口，进一步封装 CRUD 采用 get 查询单行 remove 删除 list 查询集合 page 分页 前缀命名方式区分 Mapper 层避免混淆，

泛型 T 为任意实体对象

建议如果存在自定义通用 Service 方法的可能，请创建自己的 IBaseService 继承 Mybatis-Plus 提供的基类

对象 Wrapper 为条件构造器

使用

Save

// 插入一条记录（选择字段，策略插入）
boolean save(T entity);
// 插入（批量）
boolean saveBatch(Collection<T> entityList);
// 插入（批量）
boolean saveBatch(Collection<T> entityList, int batchSize);

注意：service的插入返回的是布尔类型

批次插入

SaveOrUpdate

// TableId 注解存在更新记录，否插入一条记录
boolean saveOrUpdate(T entity);
// 根据updateWrapper尝试更新，否继续执行saveOrUpdate(T)方法
boolean saveOrUpdate(T entity, Wrapper<T> updateWrapper);
// 批量修改插入
boolean saveOrUpdateBatch(Collection<T> entityList);
// 批量修改插入
boolean saveOrUpdateBatch(Collection<T> entityList, int batchSize);

//TableId 注解存在更新记录，否则插入一条记录
singerService.saveOrUpdate(singer);
singer.setAge(16);
//这里wrapper为null会更新所有数据，慎用。。。我
singerService.saveOrUpdate(singer,null);

saveOrUpdate()这里要注意：

entity如果没有id会直插入

如果有id会先查询数据有就更新没有则执行插入

如果还传了wrapper要注意null值会导致对所有数据更新

Remove

// 根据 entity 条件，删除记录
boolean remove(Wrapper<T> queryWrapper);
// 根据 ID 删除
boolean removeById(Serializable id);
// 根据 columnMap 条件，删除记录
boolean removeByMap(Map<String, Object> columnMap);
// 删除（根据ID 批量删除）
boolean removeByIds(Collection<? extends Serializable> idList);

Update

// 根据 UpdateWrapper 条件，更新记录 需要设置sqlset
boolean update(Wrapper<T> updateWrapper);
// 根据 whereWrapper 条件，更新记录
boolean update(T updateEntity, Wrapper<T> whereWrapper);
// 根据 ID 选择修改
boolean updateById(T entity);
// 根据ID 批量更新
boolean updateBatchById(Collection<T> entityList);
// 根据ID 批量更新
boolean updateBatchById(Collection<T> entityList, int batchSize);

这两和mapper没多大区别，略！

Get

// 根据 ID 查询
T getById(Serializable id);
// 根据 Wrapper，查询一条记录。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")
T getOne(Wrapper<T> queryWrapper);
// 根据 Wrapper，查询一条记录
T getOne(Wrapper<T> queryWrapper, boolean throwEx);
// 根据 Wrapper，查询一条记录
Map<String, Object> getMap(Wrapper<T> queryWrapper);
// 根据 Wrapper，查询一条记录
<V> V getObj(Wrapper<T> queryWrapper, Function<? super Object, V> mapper);

@Test
void serviceGet(){QueryWrapper<Singer> wrapper=new QueryWrapper();Singer byId = singerService.getById("1556883204896604161");System.out.println("byId = " + byId);wrapper.eq("age",18);wrapper.last("LIMIT 1");singerService.getOne(wrapper,true);Singer one = singerService.getOne(wrapper);System.out.println("one = " + one);
}

getOne：结果集有多条会报异常

singerService.getOne(wrapper, false);

false则不报异常选择一条数据输出

或者加上wrapper.last(“LIMIT 1”);

Map<String, Object> getMap(Wrapper queryWrapper);

map多条返回一条数据不报错

@Test
void serviceGetMap(){QueryWrapper<Singer> wrapper=new QueryWrapper();wrapper.eq("age",18);Map<String, Object> map = singerService.getMap(wrapper);System.out.println("map = " + map);
}

// 根据 Wrapper，查询一条记录
<V> V getObj(Wrapper<T> queryWrapper, Function<? super Object, V> mapper);

这个没弄懂传的什么参数，后面再填坑吧。

List

// 查询所有
List<T> list();
// 查询列表
List<T> list(Wrapper<T> queryWrapper);
// 查询（根据ID 批量查询）
Collection<T> listByIds(Collection<? extends Serializable> idList);
// 查询（根据 columnMap 条件）
Collection<T> listByMap(Map<String, Object> columnMap);
// 查询所有列表
List<Map<String, Object>> listMaps();
// 查询列表
List<Map<String, Object>> listMaps(Wrapper<T> queryWrapper);
// 查询全部记录
List<Object> listObjs();
// 查询全部记录
<V> List<V> listObjs(Function<? super Object, V> mapper);
// 根据 Wrapper 条件，查询全部记录
List<Object> listObjs(Wrapper<T> queryWrapper);
// 根据 Wrapper 条件，查询全部记录
<V> List<V> listObjs(Wrapper<T> queryWrapper, Function<? super Object, V> mapper);

@Test
void list(){List<Singer> list = singerService.list();QueryWrapper<Singer> wrapper=new QueryWrapper();wrapper.eq("age",18);List<Singer> list2 = singerService.list(wrapper);List<Map<String, Object>> maps = singerService.listMaps();maps.forEach(System.out::println);List<Map<String, Object>> maps2 = singerService.listMaps(wrapper);maps2.forEach(System.out::println);
}

Page

// 无条件分页查询
IPage<T> page(IPage<T> page);
// 条件分页查询
IPage<T> page(IPage<T> page, Wrapper<T> queryWrapper);
// 无条件分页查询
IPage<Map<String, Object>> pageMaps(IPage<T> page);
// 条件分页查询
IPage<Map<String, Object>> pageMaps(IPage<T> page, Wrapper<T> queryWrapper);

@Test
void page(){Page<Singer> page = singerService.page(new Page<>(1, 5));page.getRecords().forEach(System.out::println);Page<Map<String, Object>> mapPage = singerService.pageMaps(new Page<>(1, 5));mapPage.getRecords().forEach(System.out::println);
}

Count

// 查询总记录数
int count();
// 根据 Wrapper 条件，查询总记录数
int count(Wrapper<T> queryWrapper);

Chain

query

// 链式查询 普通
QueryChainWrapper<T> query();
// 链式查询 lambda 式。注意：不支持 Kotlin
LambdaQueryChainWrapper<T> lambdaQuery();// 示例：
query().eq("column", value).one();
lambdaQuery().eq(Entity::getId, value).list();

@Test
void query(){Long count = singerService.query().eq("age", 18).count();List<Singer> list = singerService.lambdaQuery().eq(Singer::getName, "周杰伦").list();list.forEach(System.out::println);
}

update

// 链式更改 普通
UpdateChainWrapper<T> update();
// 链式更改 lambda 式。注意：不支持 Kotlin
LambdaUpdateChainWrapper<T> lambdaUpdate();// 示例：
update().eq("column", value).remove();
lambdaUpdate().eq(Entity::getId, value).update(entity);

@Test
void update(){Singer singer = new Singer();singer.setName("周杰伦2");singer.setAge(18);singer.setOther("爱你穿越时间，两行来自秋末的眼泪");singerService.update().eq("age", 18).remove();singerService.lambdaUpdate().eq(Singer::getName,"周杰伦2").update(singer);
}

完整代码

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.example.mp_demo.entity.Singer;
import com.example.mp_demo.mapper.SingerMapper;
import com.example.mp_demo.service.SingerService;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;@SpringBootTest
class MpDemoApplicationTests {@Autowiredprivate SingerMapper singerMapper;@Autowiredprivate SingerService singerService;@Testvoid mapperInsert() {Singer singer = new Singer();singer.setName("陶喆");singer.setAge(22);singer.setOther("空无一人 这片沙滩~");int i = singerMapper.insert(singer);System.out.println("i = " + i);}@Testvoid mapperSelectById() {String id1 = "1556577794717298690";String id2 = "1556592930551185410";String id3 = "1556593922332053506";List<String> ids = new ArrayList<>();ids.add(id1);ids.add(id2);ids.add(id3);Singer singer = singerMapper.selectById(id1);System.out.println("===================根据单个id查询：\n" + singer.toString());List<Singer> singers = singerMapper.selectBatchIds(ids);System.out.println("===================根据多个id查询：");singers.forEach(System.out::println);}@Testvoid mapperSelectOne() {QueryWrapper<Singer> wrapper = new QueryWrapper<>();wrapper.eq("age",18);Singer singer = singerMapper.selectOne(wrapper);System.out.println("singer = " + singer.toString());}@Testvoid mapperSelectList() {List<Singer> singers = singerMapper.selectList(null);singers.forEach(System.out::println);}@Testvoid mapperSelectByMap() {Map map=new HashMap<>();map.put("age",18);List<Singer> singers = singerMapper.selectByMap(map);singers.forEach(System.out::println);}@Testvoid mapperSelectMaps() {List<Map<String, Object>> maps = singerMapper.selectMaps(null);maps.forEach(System.out::println);}@Testvoid mapperSelectObjs() {List<Object> objects = singerMapper.selectObjs(null);objects.forEach(System.out::println);}@Testvoid mapperSelectPage() {IPage<Singer> singerIPage = singerMapper.selectPage(new Page<>(1,10), null);singerIPage.getRecords().forEach(System.out::println);}@Testvoid mapperSelectMapsPage() {Page<Map<String, Object>> mapPage = singerMapper.selectMapsPage(new Page<>(1, 10), null);mapPage.getRecords().forEach(System.out::println);}@Testvoid mapperSelectCount() {Long count = singerMapper.selectCount(null);System.out.println("count = " + count);}@Testvoid mapperUpdate() {QueryWrapper<Singer> wrapper = new QueryWrapper<>();wrapper.eq("age",17);Singer singer = singerMapper.selectOne(wrapper);System.out.println("singer.toString() = " + singer.toString());singer.setOther("改一下");singerMapper.update(singer,wrapper);System.out.println("=============================update======================================");List<Singer> singers = singerMapper.selectList(null);singers.forEach(System.out::println);}@Testvoid mapperUpdateById() {QueryWrapper<Singer> wrapper = new QueryWrapper<>();wrapper.eq("age",17);Singer singer = singerMapper.selectOne(wrapper);System.out.println("singer.toString() = " + singer.toString());singer.setOther("改回来");singerMapper.updateById(singer);System.out.println("=============================update======================================");List<Singer> singers = singerMapper.selectList(null);singers.forEach(System.out::println);}@Testvoid mapperDelete(){QueryWrapper<Singer> wrapper = new QueryWrapper<>();wrapper.eq("age",22);singerMapper.delete(wrapper);System.out.println("=============================delete======================================");List<Singer> singers = singerMapper.selectList(null);singers.forEach(System.out::println);}@Testvoid mapperDeleteBatchsIds(){ArrayList<String> ids = new ArrayList<>();ids.add("1556830638657703938");singerMapper.deleteBatchIds(ids);System.out.println("=============================delete======================================");List<Singer> singers = singerMapper.selectList(null);singers.forEach(System.out::println);}@Testvoid mapperDeleteByMap(){Map<String,Object> map=new HashMap<>();map.put("age",22);singerMapper.deleteByMap(map);System.out.println("=============================delete======================================");List<Singer> singers = singerMapper.selectList(null);singers.forEach(System.out::println);}@Testvoid serviceSave() {Singer singer = new Singer();singer.setName("周杰伦2");singer.setAge(18);singer.setOther("爱你穿越时间，两行来自秋末的眼泪");boolean save = singerService.save(singer);System.out.println("save = " + save);}@Testvoid serviceSaveBatch() {Singer singer1 = new Singer();singer1.setName("周杰伦7");singer1.setAge(18);singer1.setOther("不懂你的黑色幽默");Singer singer2 = new Singer();singer2.setName("周杰伦8");singer2.setAge(18);singer2.setOther("周杰伦周杰伦周杰伦周杰伦周杰伦，你的完美主义太彻底");List<Singer> singers=new ArrayList<>();singers.add(singer1);singers.add(singer2);boolean save = singerService.saveBatch(singers,1);System.out.println("save = " + save);List<Singer> list = singerService.list();list.forEach(System.out::println);}@Testvoid serviceSaveOrUpdate(){Singer singer = new Singer();singer.setId("214124123");singer.setName("周杰伦001");singer.setAge(15);singer.setOther("爱像一阵风");singerService.saveOrUpdate(singer);singer.setAge(16);// singerService.saveOrUpdate(singer,null);}@Testvoid serviceSaveOrUpdateBatch(){Singer singer = new Singer();singer.setName("周杰伦2");singer.setAge(18);singer.setOther("爱你穿越时间，两行来自秋末的眼泪");Singer singer3 = new Singer();singer3.setName("周杰伦7");singer3.setAge(18);singer3.setOther("不懂你的黑色幽默");Singer singer2 = new Singer();singer2.setName("周杰伦8");singer2.setAge(18);singer2.setOther("周杰伦周杰伦周杰伦周杰伦周杰伦，你的完美主义太彻底");Singer singer4 = new Singer();singer4.setName("周杰伦9");singer4.setAge(16);singer4.setOther("我的城堡说欢迎光临");List list=new ArrayList();list.add(singer);list.add(singer2);list.add(singer3);list.add(singer4);singerService.saveOrUpdateBatch(list);}@Testvoid serviceGet(){QueryWrapper<Singer> wrapper=new QueryWrapper();Singer byId = singerService.getById("1556883204896604161");System.out.println("byId = " + byId);wrapper.eq("age",18);wrapper.last("LIMIT 1");singerService.getOne(wrapper,true);Singer one = singerService.getOne(wrapper);System.out.println("one = " + one);}@Testvoid serviceGetMap(){QueryWrapper<Singer> wrapper=new QueryWrapper();wrapper.eq("age",18);Map<String, Object> map = singerService.getMap(wrapper);System.out.println("map = " + map);}@Testvoid list(){List<Singer> list = singerService.list();QueryWrapper<Singer> wrapper=new QueryWrapper();wrapper.eq("age",18);List<Singer> list2 = singerService.list(wrapper);List<Map<String, Object>> maps = singerService.listMaps();maps.forEach(System.out::println);List<Map<String, Object>> maps2 = singerService.listMaps(wrapper);maps2.forEach(System.out::println);}@Testvoid page(){Page<Singer> page = singerService.page(new Page<>(1, 5));page.getRecords().forEach(System.out::println);Page<Map<String, Object>> mapPage = singerService.pageMaps(new Page<>(1, 5));mapPage.getRecords().forEach(System.out::println);}@Testvoid query(){Long count = singerService.query().eq("age", 18).count();List<Singer> list = singerService.lambdaQuery().eq(Singer::getName, "周杰伦").list();list.forEach(System.out::println);}@Testvoid update(){Singer singer = new Singer();singer.setName("周杰伦2");singer.setAge(18);singer.setOther("爱你穿越时间，两行来自秋末的眼泪");singerService.update().eq("age", 18).remove();singerService.lambdaUpdate().eq(Singer::getName,"周杰伦2").update(singer);}
}