如何在jersey/hk2应用程序中正确配置EntityManager？

Question

我有一个使用JPA持久性的jersey-2/hk2应用程序.将EntityManager在这样的约束启动

public MyApplication() {
    // ...
    register(new AbstractBinder() {
        @Override
        public void configure() {
          bindFactory(EmFactory.class)
            .to(EntityManager.class)
            .in(RequestScoped.class);
        }
    });
}

与工厂类一样

public class EmFactory implements Factory<EntityManager> {

    private static final String PERSISTENCE_UNIT = "unit";

    private EntityManagerFactory emf;
    private CloseableService closeableService;

    @Inject
    public EmFactory(@Named(PERSISTENCE_UNIT) String persistenceUnit,
            CloseableService closeableService) {
        emf = Persistence.createEntityManagerFactory(persistenceUnit);
        this.closeableService = closeableService;
    }

    @Override
    public EntityManager provide() {
        final EntityManager entityManager = emf.createEntityManager();
        closeableService.add(new Closeable() {

            @Override
            public void close() throws IOException {
                if(entityManager.isOpen()) {
                    entityManager.close();
                }
            }
        });
        return entityManager;
    }

    @Override
    public void dispose(EntityManager entityManager) {
        if(entityManager.isOpen()) {
            entityManager.close();
        }
    }
}

这工作,但然后对于每个请求我在日志中收到有关已注册的EntityManager的警告:

HHH000436: Entity manager factory name (unit) is already registered. \
  If entity manager will be clustered or passivated, specify a unique \
  value for property 'hibernate.ejb.entitymanager_factory_name'

我究竟做错了什么？在jersey-2/hk2应用程序中初始化EntityManager的正确方法是什么？

Answer 1

一种选择是不是创建一个新的EntityManagerFactory中EMFactory(这是在请求范围内),您可以创建为一个单独的工厂EntityManagerFactory,然后就注射EntityManagerFactory到EMFactory.

public class EMFFactory implements Factory<EntityManagerFactory> {
    private final EntityManagerFactory emf;
    public EMFFactory (){
        emf = Persistence.createEntityManagerFactory(persistenceUnit);
    }
    public EntityManagerFactory provide() {
        return emf;
    }
    ...
}

public class EMFactory implements Factory<EntityManager> {
    private final EntityManager em;

    @Inject
    public EMFactory (EntityManagerFactory emf){
        em = emf.createEntityManager();
    }
    public EntityManager provide() {
        return em;
    }
    ...
}

没有测试过这个确切的实现,但它看起来应该是这样的.我以前用过这种模式.

register(new AbstractBinder() {
    @Override
    public void configure() {
      bindFactory(EMFFactory.class).to(EntityManagerFactory.class).in(Singleton.class);
      bindFactory(EMFactory.class).to(EntityManager.class).in(RequestScoped.class);
    }
});

UPDATE

关于上述例子需要注意的一点是,它不会清理资源,即EntityManager应该关闭; 它不会自行关闭.我们需要覆盖类中的一个dispose方法Factory,但根据我的经验,Jersey从不调用它.

我们能做的是添加EntityManager到[ CloseableService] [1]

public class EMFactory implements Factory<EntityManager> {
    private final EntityManagerFactory emf;
    private final CloseableService closeService;

    @Inject
    public EMFactory (EntityManagerFactory emf, CloseableService closeService){
        this.emf = emf;
        this.closeService = closeService;
    }
    public EntityManager provide() {
        final EntityManager em = emf.createEntityManager();
        this.closeService.add(new Closeable(){
            @Override
            public void close() {
                em.close();
            }
        });
        return em;
    }
    ...
}

这样EntityManager就确保在请求结束时关闭.