Mybatis

MP使用
1、在maven 中导入依赖

 
      com.baomidou
      mybatis-plus-boot-starter
      ${yourVersion}
  

2、创建接口

public interface UserMapper extends baseMapper {
}

3、测试中创建操作

@SpringBootTest
class testOfMP{

    @Resource 
    private UserMapper userMapper;

    @Test
    void testSelectList() {
    	// 查询所有
        List users = userMapper.selectList(null);
        users.forEach(System.out::println);
    }

    @Test
    public void testInsert() {
        User user = new User();
        user.setName("Helen");
        user.setAge(18);
        int result = userMapper.insert(user); //插入用户
        System.out.println("影响的行数：" + result); //影响的行数
        System.out.println("id：" + user.getId()); //id自动回填

    }

    @Test
    public void testSelect() {
    
        //按id查询
        User user = userMapper.selectById(1);
        System.out.println(user);

        //按照id列表查询
        List users = userMapper.selectBatchIds(Arrays.asList(1, 2, 3));
        users.forEach(System.out::println);

        //按条件查询
        HashMap stringObjectHashMap = new HashMap<>();
        stringObjectHashMap.put("name", "Helen");
        stringObjectHashMap.put("age", 18);
        List users1 = userMapper.selectByMap(stringObjectHashMap);
        users1.forEach(System.out::println);

    }


    @Test
    public void testUpdate() {
        User user = new User();
        user.setId(1L);
        user.setAge(28);
        //注意：update时生成的sql自动是动态sql
        //修改操作
        int result = userMapper.updateById(user);
        System.out.println("影响的行数：" + result);
    }

    @Test
    public void testDelete() {
    	//删除操作
        int result = userMapper.deleteById(5);
        System.out.println("影响的行数：" + result);
    }

通用Service
MP中有一个接口 IService和其实现类 ServiceImpl，封装了常见的业务层逻辑
使用方式：
1、创建Service接口

public interface UserService extends IService {
}

2、创建Service实现类

@Service
public class UserServiceImpl extends ServiceImpl implements UserService {
}

3、创建测试类

@SpringBootTest
public class ServiceTests {
    @Resource
    private UserService userService;

	@Test
	public void testCount(){
	    int count = userService.count();
	    System.out.println("总记录数：" + count);
	}
	
	@Test
	public void testSaveBatch(){
	    // SQL长度有限制，海量数据插入单条SQL无法实行，
	    // 因此MP将批量插入放在了通用Service中实现，而不是通用Mapper
	    ArrayList users = new ArrayList<>();
	    for (int i = 0; i < 5; i++) {
	        User user = new User();
	        user.setName("Helen" + i);
	        user.setAge(10 + i);
	        users.add(user);
	    }
	    userService.saveBatch(users);
	}
}