【Mybatis-Plus】 Mapper 接口使用总结

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已于 2023-07-11 20:54:35 修改

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分类专栏： Mybatis-Plus 文章标签： mybatis

于 2023-07-11 15:46:24 首次发布

本文链接：https://blog.youkuaiyun.com/Java_Wxlin/article/details/131661951

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本文展示了如何使用MyBatisPlus的Mapper接口进行数据库的基本CRUD操作，包括插入、删除（按条件、按ID和批量）、更新（按条件、按ID）和查询（按ID、按条件、批量和分页）。每个操作都附带了对应的SQL执行情况和返回结果。

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本文主要内容是 Mapper接口的使用示例。

注意：我们需要方法执行的SQL 是什么样的，以及返回值。

Mapper CRUD 接口

新增

insert方法

==>  Preparing: INSERT INTO user ( user_id, user_name, create_time ) VALUES ( ?, ?, ? ) 
==> Parameters: halo(String), 哈喽啊(String), 2023-07-11 14:01:59.864(Timestamp)
<==    Updates: 1

删除

delete

根据 entity 条件，删除记录

注意：queryWrapper后面可以跟条件构造器

@Test
public void delete() {
    QueryWrapper queryWrapper = new QueryWrapper<>();
    System.out.println(userDao.delete(queryWrapper));
}

==>  Preparing: DELETE FROM user 
==> Parameters: 
<==    Updates: 1

deleteBatchIds

删除（根据ID 批量删除）

@Test
public void deleteBatchIds() {
    List<Integer>  deleteIds = new ArrayList<>();
    deleteIds.add(1);
    deleteIds.add(2);
    deleteIds.add(3);
    System.out.println(userDao.deleteBatchIds(deleteIds));
}

==>  Preparing: DELETE FROM user WHERE id IN ( ? , ? , ? ) 
==> Parameters: 1(Integer), 2(Integer), 3(Integer)
<==    Updates: 1

deleteById

根据 ID 删除

 @Test
public void deleteById(){
        Integer id=1;
        System.out.println(userDao.deleteById(id));
}

执行的SQL语句

==>  Preparing: DELETE FROM user WHERE id=? 
==> Parameters: 1(Integer)
<==    Updates: 0

deleteByMap

根据 columnMap 条件，删除记录

  @Test
    public void deleteByMap() {
        Map<String,Object> params = new HashMap<>();
        params.put("user_id","halo");
        System.out.println(userDao.deleteByMap(params));
    }

==>  Preparing: DELETE FROM user WHERE user_id = ? 
==> Parameters: halo(String)
<==    Updates: 0

修改

update

根据 whereWrapper 条件，更新记录

@Test
public void update() {
    User user = new User();
    user.setUserId("tony");
    QueryWrapper queryWrapper = new QueryWrapper();
    System.out.println(userDao.update(user,queryWrapper));
}

==>  Preparing: UPDATE user SET user_id=? 
==> Parameters: tony(String)
<==    Updates: 1

updateById

根据 ID 修改

@Test
    public void updateById() {
        User user = new User();
        user.setUserId("halo");
        user.setUserName("哈喽啊");
        user.setCreateTime(new Date());
        user.setId(1);
        System.out.println(userDao.updateById(user));
    }

==>  Preparing: UPDATE user SET user_id=?, user_name=?, create_time=? WHERE id=? 
==> Parameters: halo(String), 哈喽啊(String), 2023-07-11 14:17:01.184(Timestamp), 1(Integer)
<==    Updates: 0

查询

selectById
根据 ID 查询

  @Test
    public void selectById() {
        Integer i = 1;
        System.out.println(userDao.selectById(i));
    }

==>  Preparing: SELECT id,user_id,user_name,create_time,dept_id FROM user WHERE id=? 
==> Parameters: 1(Integer)
<==      Total: 0

selectOne

根据 entity 条件，查询一条记录

注意：如果查询出来的记录是多条的话，会报错的哦

 @Test
public void selectOne() {
        System.out.println(userDao.selectOne(new QueryWrapper<User>().eq("user_id","halo")));
}

==>  Preparing: SELECT id,user_id,user_name,create_time,dept_id FROM user WHERE (user_id = ?) 
==> Parameters: halo(String)
<==      Total: 0

selectBatchIds

查询（根据ID 批量查询）

@Test
public void selectBatchIds() {
    List<Integer> list = new ArrayList<>();
    list.add(1);
    list.add(2);
     userDao.selectBatchIds(list);   
}

==>  Preparing: SELECT id,user_id,user_name,create_time,dept_id FROM user WHERE id IN ( ? , ? ) 
==> Parameters: 1(Integer), 2(Integer)
<==      Total: 0

selectList

根据 entity 条件，查询全部记录

 @Test
public void selectList() {
    System.out.println(userDao.selectList(new QueryWrapper<>()));
}

==>  Preparing: SELECT id,user_id,user_name,create_time,dept_id FROM user 
==> Parameters: 
<==    Columns: id, user_id, user_name, create_time, dept_id
<==        Row: 5, tony, 哈喽啊, 2023-07-11 14:11:20.0, null
<==        Row: 6, halo1, 哈喽啊2, 2023-07-11 14:35:42.0, null
<==        Row: 7, halo3, 哈喽啊24, 2023-07-11 14:35:51.0, null
<==      Total: 3

selectByMap

查询（根据 columnMap 条件）

注意：这里的返回值与selectMaps 返回值的区别哦

@Test
public void selectByMap() {
    Map<String,Object> params = new HashMap();
    params.put("user_id","halo");
    System.out.println(userDao.selectByMap(params));
}

==>  Preparing: SELECT id,user_id,user_name,create_time,dept_id FROM user 
==> Parameters: 
<==    Columns: id, user_id, user_name, create_time, dept_id
<==        Row: 5, tony, 哈喽啊, 2023-07-11 14:11:20.0, null
<==        Row: 6, halo1, 哈喽啊2, 2023-07-11 14:35:42.0, null
<==        Row: 7, halo3, 哈喽啊24, 2023-07-11 14:35:51.0, null
<==      Total: 3
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@a451491]
[User(id=5, userId=tony, userName=哈喽啊, createTime=Tue Jul 11 14:11:20 CST 2023, deptId=null), 
User(id=6, userId=halo1, userName=哈喽啊2, createTime=Tue Jul 11 14:35:42 CST 2023, deptId=null), 
User(id=7, userId=halo3, userName=哈喽啊24, createTime=Tue Jul 11 14:35:51 CST 2023, deptId=null)]

selectMaps

查询（根据 columnMap 条件）

注意返回值哦

  @Test
public void selectMaps() {
  List<Map<String, Object>>  list = userDao.selectMaps(new QueryWrapper<>());
  System.out.println(list);
}

==>  Preparing: SELECT id,user_id,user_name,create_time,dept_id FROM user 
==> Parameters: 
<==    Columns: id, user_id, user_name, create_time, dept_id
<==        Row: 5, tony, 哈喽啊, 2023-07-11 14:11:20.0, null
<==        Row: 6, halo1, 哈喽啊2, 2023-07-11 14:35:42.0, null
<==        Row: 7, halo3, 哈喽啊24, 2023-07-11 14:35:51.0, null
<==      Total: 3
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@a451491]
[{create_time=2023-07-11 14:11:20.0, user_id=tony, user_name=哈喽啊, id=5},
 {create_time=2023-07-11 14:35:42.0, user_id=halo1, user_name=哈喽啊2, id=6}, 
 {create_time=2023-07-11 14:35:51.0, user_id=halo3, user_name=哈喽啊24, id=7}]

selectObjs

根据 Wrapper 条件，查询全部记录。注意：只返回第一个字段的值

@Test
public void selectObjs() {
    List<Object> list =  userDao.selectObjs(new QueryWrapper<>());
    System.out.println(list);
}

==>  Preparing: SELECT id,user_id,user_name,create_time,dept_id FROM user 
==> Parameters: 
<==    Columns: id, user_id, user_name, create_time, dept_id
<==        Row: 5, tony, 哈喽啊, 2023-07-11 14:11:20.0, null
<==        Row: 6, halo1, 哈喽啊2, 2023-07-11 14:35:42.0, null
<==        Row: 7, halo3, 哈喽啊24, 2023-07-11 14:35:51.0, null
<==      Total: 3
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7ceb4478]
[5, 6, 7]

selectPage

根据 entity 条件，查询全部记录（并翻页）

注意；这里我们需要配置一下分页哦

@Configuration
public class MyBatisPlusConfig {
    /**
     * 分页插件
     */
    @Bean
    public PaginationInterceptor paginationInterceptor() {
        return new PaginationInterceptor();
    }
}

 @Test
public void selectPage() {
        Page page = new Page();
        page.setCurrent(1);
        page.setPages(10);
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.eq("user_id","tony");
        IPage<Map<String, Object>> iPage = userDao.selectPage(page,queryWrapper);
        System.out.println(iPage.toString());
        }

JsqlParserCountOptimize sql=SELECT  id,user_id,user_name,create_time,dept_id  FROM user 
 
 WHERE (user_id = ?)
==>  Preparing: SELECT COUNT(1) FROM user WHERE (user_id = ?) 
==> Parameters: tony(String)
<==    Columns: COUNT(1)
<==        Row: 1
==>  Preparing: SELECT id,user_id,user_name,create_time,dept_id FROM user WHERE (user_id = ?) LIMIT ?,? 
==> Parameters: tony(String), 0(Long), 10(Long)
<==    Columns: id, user_id, user_name, create_time, dept_id
<==        Row: 5, tony, 哈喽啊, 2023-07-11 14:11:20.0, null
<==      Total: 1

selectMapsPage

根据 Wrapper 条件，查询全部记录（并翻页）

   @Test
    public void selectMapsPage() {
        Page page = new Page();
        page.setCurrent(1);
        page.setPages(10);
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.eq("user_id","tony");
        IPage<Map<String, Object>> iPage = userDao.selectMapsPage(page,queryWrapper);
        System.out.println(iPage);
    }

JsqlParserCountOptimize sql=SELECT  id,user_id,user_name,create_time,dept_id  FROM user 
 
 WHERE (user_id = ?)
==>  Preparing: SELECT COUNT(1) FROM user WHERE (user_id = ?) 
==> Parameters: tony(String)
<==    Columns: COUNT(1)
<==        Row: 1
==>  Preparing: SELECT id,user_id,user_name,create_time,dept_id FROM user WHERE (user_id = ?) LIMIT ?,? 
==> Parameters: tony(String), 0(Long), 10(Long)
<==    Columns: id, user_id, user_name, create_time, dept_id
<==        Row: 5, tony, 哈喽啊, 2023-07-11 14:11:20.0, null
<==      Total: 1

selectCount

根据 Wrapper 条件，查询总记录数

@Test
public void selectCount() {
    System.out.println(userDao.selectCount(new QueryWrapper<>()));
}

==>  Preparing: SELECT COUNT( 1 ) FROM user 
==> Parameters: 
<==    Columns: COUNT( 1 )
<==        Row: 3
<==      Total: 1