MybatisPlus QueryWrapper常用方法实例

@Test

public void testQuery() {

QueryWrapper<User> queryWrapper = new QueryWrapper<>();

     queryWrapper

             .isNull( "name" )

             .ge( "age" , 12 )

             .isNotNull( "email" );

         int result = userMapper.delete(queryWrapper);

     System.out.println( "delete return count = " + result);

}

@Test

public void testSelectOne() {

     QueryWrapper<User> queryWrapper = new QueryWrapper<>();

     queryWrapper.eq( "name" , "Tom" );

     Useruser = userMapper.selectOne(queryWrapper); //只能返回一条记录，多余一条则抛出异常

     System.out.println(user);

}

@Test

public void testSelectCount() {

     QueryWrapper<User> queryWrapper = new QueryWrapper<>();

     queryWrapper.between( "age" , 20 , 30 );

         Integer count = userMapper.selectCount(queryWrapper); //返回数据数量

     System.out.println(count);

}

@Test

public void testSelectMaps() {

     QueryWrapper<User> queryWrapper = new QueryWrapper<>();

     queryWrapper

             .select( "name" , "age" )

             .like( "name" , "e" )

             .likeRight( "email" , "5" );

     List<Map<String, Object>> maps = userMapper.selectMaps(queryWrapper); //返回值是Map列表

     maps.forEach(System.out::println);

}

@Test

public void testSelectListOrderBy() {

     QueryWrapper<User> queryWrapper = new QueryWrapper<>();

     queryWrapper.orderByDesc( "age" , "id" );

     List<User>users = userMapper.selectList(queryWrapper);

     users.forEach(System.out::println);

}

@Test

public void save() {

     User user = new User();

     user.setAge( 23 );

     user.setEmail( "344" );

     user.setName( "test" );

     // 1.使用service新增

     userService.save(user);

     // 2.使用mapper 新增

     userMapper.insert(user);

}

@Test

public void delete() {

     // 根据条件删除

     userService.remove(Wrappers.<User>query().lambda().eq(User::getAge, 3 ));

}

@Test

public void update() {

    User user = new User();

    user.setAge( 23 );

    user.setEmail( "344" );

    user.setName( "test333" );

    UpdateWrapper<User> updateWrapper = new UpdateWrapper<>();

    updateWrapper.eq( "id" , "1" );

    // 1.user 中封装修改的属性值， updateWrapper 中封装修改的条件参数值

    userService.update(user,updateWrapper);

    // 2.根据条件修改对应的参数属性值

    userService.update(Wrappers.<User>update().lambda().set(User::getName, "2" ).eq(User::getAge, 23 ));　　　　

    // 3.判断参数是否为空,并进行修改　　　　 String name = "name";　　　　 userService.update(Wrappers.<User>update().lambda().set(StringUtils.isNotBlank(name),User::getName, name).eq(User::getAge, 23));

}