Mybatis的优雅写法

川长思鸟来 2024-03-26 08:02 27阅读 0赞

//1、查询
    //1.1、根据id查询
    User user = userMapper.selectById(1L);
    System.out.println("userMapper.selectById=" + user);
    
    //1.2、自定义条件查询
    LambdaQueryWrapper<User> lambdaQueryWrapper = Wrappers.lambdaQuery(User.class).eq(User::getId, 1L);
    User user1 = userMapper.selectOne(lambdaQueryWrapper);
    System.out.println("userMapper.selectOne=" + user1);
    User user2 = userService.getOne(lambdaQueryWrapper);
    System.out.println("userService.getOne=" + user2);
    
    //1.3、列表查询
    LambdaQueryWrapper<User> lambdaQueryWrapper2 = Wrappers.lambdaQuery(User.class).eq(User::getName, "测试");
    List<User> userList1 = userMapper.selectList(lambdaQueryWrapper2);
    System.out.println("userMapper.selectList=" + userList1);
    List<User> userList2 = userService.list(lambdaQueryWrapper2);
    System.out.println("userService.list=" + userList2);
    
    //1.4、多条件查询：SELECT id, version, name, age, email, create_time, update_time, deleted FROM user
    // WHERE deleted = 'N'
    // AND (id > ?
    //      AND (name = ? OR (age = ? AND id = ?))
    //      AND id < ?
    // ) AND tenant = 'fivestar'
    //列表查询
    LambdaQueryWrapper<User> lambdaQueryWrapper3 = Wrappers.lambdaQuery(User.class)
            .gt(User::getId,1L)
            .and(userLambdaQueryWrapper -> {
                userLambdaQueryWrapper.eq(User::getName, "测试");
    
                userLambdaQueryWrapper.or(userLambdaQueryWrapper1 -> {
                    userLambdaQueryWrapper1
                            .eq(User::getAge, 28)
                            .eq(User::getId, 2L);
                });
            })
            .lt(User::getId,100L);
    
    List<User> userList3 = userMapper.selectList(lambdaQueryWrapper3);
    
    
    //2、更新
    
    //2.1、通过mapper更新
    User user = new User();
    user.setName("韦 昌 龙-代码修改时间");
    user.setAge(16);
    
    LambdaUpdateWrapper<User> lambdaUpdateWrapper = lambdaUpdate(User.class).eq(User::getId, 6L);
    int i = userMapper.update(user, lambdaUpdateWrapper);
    System.out.println("受影响的行数：" + i);
        
    //2.2、通过service更新（底层调用的mapper方法）
    LambdaUpdateWrapper<User> lambdaUpdateWrapper2 = lambdaUpdate(User.class)
                .set(User::getAge,17L)
                .eq(User::getId, 6L);
    Boolean flag = userService.update(lambdaUpdateWrapper2);
    
    
    //3、删除
    LambdaQueryWrapper<User> lambdaQueryWrapper = Wrappers.lambdaQuery(User.class).eq(User::getId, 6L);
    userMapper.delete(lambdaQueryWrapper);