Mybatis-plus的简单用法

基于BaseMapper<User> (指定泛型为你操作的对象)

引入依赖

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.3.1</version>
</dependency>

 自定义mapper继承BaseMapper接口

public interface UserMapper extends BaseMapper<User> {}

简单sql语句

 复杂sql语句(Wrapper)

 例如:查询出名字中带o的，存款大于等于1000元的人的id、username、info、balance字段

@Test
    void testQueryWrapper(){
        QueryWrapper<User> wrapper = new QueryWrapper<User>()
                 .select("id", "username", "info", "balance")
                .like("username", "o")
                .ge("balance", 1000);
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
    }

基于IService

接口:

public interface IUserService extends IService<User> {
}

实现类:

@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements IUserService {
}

 IService方法:

 简单查询:

   新增用户,删除用户,根据id查询用户

 @ApiOperation("新增用户接口")
    @PostMapping
    public void saveUser(@RequestBody UserFormDTO userDTO){
        //把DTO拷贝到PO
        User user= BeanUtil.copyProperties(userDTO, User.class);
        //新增
        userService.save(user);
    }

    @ApiOperation("删除用户接口")
    @DeleteMapping("{id}")       //路径占位符 @PathVariable
    public void deleteUserById(@ApiParam("用户id") @PathVariable Long id) {

        userService.removeById(id);
    }

    @ApiOperation("根据id查询用户接口")
    @GetMapping("{id}")       //路径占位符 @PathVariable
    public UserVO queryUserById(@ApiParam("用户id") @PathVariable Long id) {
        User user= userService.getById(id);
        return BeanUtil.copyProperties(user, UserVO.class);
    }

    @ApiOperation("根据id批量查询用户接口")
    @GetMapping
    public List<UserVO> queryUserByIds(@ApiParam("用户id集合") @RequestParam List<Long> ids) {
        //查询用户PO
        List<User> users=userService.listByIds(ids);
        //把po拷贝到vo
        return BeanUtil.copyToList(users, UserVO.class);
    }