如何在 jersey/hk2 应用程序中正确配置 EntityManager? [英] How do I properly configure an EntityManager in a jersey / hk2 application?

问题描述

我有一个 jersey-2/hk2 应用程序，它使用 JPA 持久性.EntityManager 像这样在启动时绑定

I have a jersey-2 / hk2 application which uses JPA persistence. The EntityManager is bound at startup like this

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

工厂类是

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();
        }
    }
}

这有效，但是对于每个请求，我都会在日志中收到有关 EntityManager 已注册的警告:

this works but then for each request i get a warning in the logs about an EntityManager being already registered:

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?

What am I doing wrong? What is the proper way to initialize an EntityManager in a jersey-2 / hk2 application?

推荐答案

一种选择是在 EMFactory(在请求中)而不是创建一个新的 EntityManagerFactory范围)，您可以为 EntityManagerFactory 创建一个单例工厂，然后只需将 EntityManagerFactory 注入 EMFactory.

One option is to instead of creating a new EntityManagerFactory in the EMFactory (which is in a request scope), you could create a singleton factory for the EntityManagerFactory, then just inject the EntityManagerFactory into the 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;
    }
    ...
}

还没有测试过这个确切的实现，但它应该看起来像这样.我以前用过这种模式.

Haven't tested this exact implementation out, but it should look something like this. I've used this pattern before.

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);
    }
});

<小时>

更新

关于上面的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.Factory 类中有一个 dispose 方法，我们需要重写它，但根据我的经验，Jersey 永远不会调用它.

---

UPDATE

One thing to note about the above example is that it doesn't clean up resources, i.e. the EntityManager should be close; it won't close itself. There is a dispose method in the Factory class that we need to override, but from my experience, this is never called by Jersey.

我们可以做的是将 EntityManager 添加到 [CloseableService][1]

What we can do is add the EntityManager to a [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;
    }
    ...
}

这样可以确保 EntityManager 在请求结束时关闭.

This way the EntityManager is ensured to be closed at the end of the request.

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