@Transactional(readOnly = true)作用

@Service
@Slf4j
@Transactional(readOnly = true)
public class LikeServiceImpl implements LikeService {
          
   

    @Autowired
    private LikeMapper likeMapper;

    @Override
    @Transactional(readOnly = false)
    public void saveOrDeleteAll() {
          
   
    }

    @Override
    public List<UserLike> getAll(){
          
   
        return likeMapper.getAll();
    }

    @Transactional(readOnly = false)
    @Override
    public void update(UserLike userLike){
          
   
        likeMapper.update(userLike);
    }

}

@SpringBootTest
class LikeServiceImplTest {
          
   

    @Autowired
    LikeService likeService;

    @Test
    void saveOrDeleteAll() {
          
   
        likeService.saveOrDeleteAll();
    }

    @Test
    void getAll() throws InterruptedException {
          
   
        System.out.println(likeService.getAll());
        Thread.sleep(20000);
        System.out.println(likeService.getAll());
    }

    @Test
    void update() {
          
   
        UserLike userLike = new UserLike();
        userLike.setLikeId(10101L);
        userLike.setType(0);
        likeService.update(userLike);
    }
}

readOnly = true 表示只能用作只读，如果操作里有增删改则会报错 readOnly = false 用作增删改

在上面测试案例中，我先查询，在停20秒期间做数据库修改，再查，查出来的数据是修改后的数据。