springboot中使用spring-data-jpa的save方法无法正常update

Question

使用最简单的方法进行update操作

public Merchant modifyOne(Merchant merchant) {
    return dao.save(merchant);
}

传递进来的方法参数merchant，已经设置了id和一部分属性，其他属性没有做设置(即null)

控制台中的日志中显示的是先select，再update

Hibernate: select merchant0_.ID as ID1_2_0_, ......
Hibernate: update MERCHANT set ADDRESS=?, ......

但实际update操作时，并没有把select出来的结果和方法中传递进来的参数merchant进行合并, 提示 ADDRESS can not be null

实体上也试过加上DynamicUpdate之类，但没有作用

@Entity
@DynamicInsert
@DynamicUpdate
public class Merchant implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    @Column(nullable = false, length = 200)
    private String address;
    ......
}

难道一定要在更新调用save之前，手工findOne一次，将查询结果和参数手工合并么？
求解。。。

Answer 1

查了好久，确实如 @好怕麻烦 所说，是这个样子。
至于为啥@DynamicUpdate无效还不大清楚。。。
目前能够找到的解决方案是实现自己的JpaRepository
这里给出自己的实现以作参考（springboot 1.5.6测试通过）

定义自己的ExtJpaRepository接口

@NoRepositoryBean
public interface ExtJpaRepository<T, ID extends Serializable> extends JpaRepository<T,ID> {
    /**
     * insert or dynamic update entity (will findOne first)
     * @param id entity id
     * @param entity entity
     * @return entity
     */
    T dynamicSave(ID id, T entity);
}

接口ExtJpaRepository的实现（其中getNullPropNames为自定义方法）

public class SimpleExtJpaRepository<T, ID extends Serializable> extends SimpleJpaRepository<T, ID> implements ExtJpaRepository<T, ID> {
    private final EntityManager em;

    public SimpleExtJpaRepository(JpaEntityInformation<T, ?> entityInformation, EntityManager em) {
        super(entityInformation, em);
        this.em = em;
    }

    public SimpleExtJpaRepository(Class<T> domainClass, EntityManager em) {
        super(domainClass, em);
        this.em = em;
    }

    @Override
    @Transactional
    public T dynamicSave(ID id, T entity) {
        T managedEntity = this.findOne(id);
        T mergedEntity;
        if (managedEntity == null) {
            em.persist(entity);
            mergedEntity = entity;
        } else {
            BeanUtils.copyProperties(entity, managedEntity, BeanUtil.getNullPropNames(entity));
            em.merge(managedEntity);
            mergedEntity = managedEntity;
        }
        return mergedEntity;
    }

}

实现自己的ExtJpaRepositoryFactoryBean以替代原有的JpaRepositoryFactoryBean

public class ExtJpaRepositoryFactoryBean<R extends JpaRepository<T, I>, T, I extends Serializable> extends JpaRepositoryFactoryBean<R, T, I> {
    public ExtJpaRepositoryFactoryBean(Class<? extends R> repositoryInterface) {
        super(repositoryInterface);
    }

    @Override
    protected RepositoryFactorySupport createRepositoryFactory(EntityManager em) {
        return new ExtJpaRepositoryFactory(em);
    }

}

ExtJpaRepositoryFactoryBean中所用到的ExtJpaRepositoryFactory

public class ExtJpaRepositoryFactory<T, I extends Serializable> extends JpaRepositoryFactory {
    private final EntityManager em;

    public ExtJpaRepositoryFactory(EntityManager em) {
        super(em);
        this.em = em;
    }

    @Override
    protected <T, ID extends Serializable> SimpleExtJpaRepository<?, ?> getTargetRepository(RepositoryInformation information, EntityManager entityManager) {
        JpaEntityInformation<?, Serializable> entityInformation = getEntityInformation(information.getDomainType());
        return getTargetRepositoryViaReflection(information, entityInformation, entityManager);
    }

    @Override
    protected Class<?> getRepositoryBaseClass(RepositoryMetadata metadata) {
        if (isQueryDslExecutor(metadata.getRepositoryInterface())) {
            return QueryDslJpaRepository.class;
        } else {
            return SimpleExtJpaRepository.class;
        }
    }

    private boolean isQueryDslExecutor(Class<?> repositoryInterface) {
        return QUERY_DSL_PRESENT && QueryDslPredicateExecutor.class.isAssignableFrom(repositoryInterface);
    }
}

最后，入口Application中指定使用自定义的FactoryBean

@SpringBootApplication
@EnableJpaRepositories(repositoryFactoryBeanClass = ExtJpaRepositoryFactoryBean.class)
public class StartApplication {
    public static void main(String[] args) {
        SpringApplication.run(StartApplication.class, args);
    }
}

Answer 2

先 findOne 再 save，不然需求需要将属性设置为 null 那咋整

Answer 3

BeanUtil.getNullPropNames(entity)这个方法是你自己写的？