在jpa CRUD存储库中保存和更新

Question

我有一个数据已经保存在我的数据库基于我的存储库和服务。我想保存另一个数据与邮递员只改变播放器id。但它不是创建一个新的实体数据。它更新现有的实体数据。我的问题是如何更新一个数据由我的服务当它找到一个现有的id。但当它找到一个新的id将保存一个新的数据到数据库。

这是我的回购：

@Repository
@Transactional
public interface CricketPlayerRepository extends CrudRepository<CricketPlayer,String>  {
    Optional<CricketPlayer> findCricketPlayerByName(String name);


}

这是我的服务：

@Service
public class CricketPlayerService {

    private CricketPlayerRepository cricketPlayerRepository;


    public CricketPlayerService(CricketPlayerRepository cricketPlayerRepository) {
        super();
        this.cricketPlayerRepository = cricketPlayerRepository;
    }

    public CricketPlayerService() {
    }

    public Optional<CricketPlayer> getPlayerByName(String name){
        return cricketPlayerRepository.findCricketPlayerByName(name);
    }

    public CricketPlayer save(CricketPlayer cricketPlayer){
        Optional<CricketPlayer> id = cricketPlayerRepository.findById(cricketPlayer.getPlayerId());
        if (id.isPresent()){
            //code here
        }
//        if (entityManager.isNew(cricketPlayer)) {
//            em.persist(cricketPlayer);
//            return cricketPlayer;
//        } else {
//            return em.merge(cricketPlayer);
//        }
        return cricketPlayerRepository.save(cricketPlayer);
    }

    public Iterable<CricketPlayer> findAllPlayers() {
        return cricketPlayerRepository.findAll();
    }

    public Optional<CricketPlayer> findPlayersById(String id) {
        return cricketPlayerRepository.findById(id);
    }

}

Answer 1

1）如果PlayerId是主键id，那么您应该调用merge（entity）。如果PlayerId存在，它将更新，否则它将创建新记录。

2）如果PlayrerId不是主键ID。最佳做法是避免将PlayrerId作为主键。

在postman中，您应该将数据库表主键id与playerID一起传递。然后调用merge（实体）。它将根据主键id是否为空来进行创建或更新。

例如，如果您在请求中传递了主键id。

    Entity e = new Entity();
    if (entityFromRequest.getId() != null){ //this is the db id from request
        //get the entity from db and then change the state   
        e = entity from db by using id
    }
    e.setPlayerId = entityFromRequest.getPlayerId
    merge(e);  // it will create or update record

Answer 2

hibernate（和其他框架）中的保存和更新操作基于id值。如果id存在，则合并（更新）实体，否则保存新实例。因此不能在这种情况下这样做。