使用Hibernate 4的Integrator模式和Spring的依赖注入

Question

我习惯使用Spring来执行依赖注入,如下所示:

<context:component-scan base-package="org.emmerich.myapp" />

然后用Autowired这样注释我的依赖类:

public class DependentClass {

    @Autowired
    private Dependency dependency;

}

但是,随着Hibernate 4.0的变化,我们现在建议使用新Integrator接口进行服务发现.这包括添加事件侦听器触发器如postUpdate,postDelete等

不幸的是,这与通过注释依赖项的依赖注入不能很好地协作.我有以下设置:

我已经定义了一个集成器来添加我的监听器ServiceFactory.这在文件中引用META-INF/services/org.hibernate.integrator.spi.Integrator.

public class MyIntegrator implements Integrator {

    private MyListener listener;

    public MyIntegrator() {
        listener = new MyListener();
    }

    @Override
    public void integrate(Configuration configuration,
                          SessionFactoryImplementor sessionFactory,
                          SessionFactoryServiceRegistry serviceRegistry) {
    final EventListenerRegistry eventRegistry =
        serviceRegistry.getService(EventListenerRegistry.class);

    eventRegistry.prependListeners(EventType.POST_COMMIT_INSERT, listener);

}

我也定义了类MyListener,它看起来像你典型的事件监听器.

@Component
public class MyListener implements PostInsertEventListener {

    @Autowired
    private Dependent dependent;

    public void onPostInsert(PostInsertEvent event) {
         // dependent == null
    }

}

不幸的是,正如评论所示,这不起作用.我想这是因为我在MyListener内部实例化MyIntegrator,它不会拾取组件而不会自动装配组件.但是,如果我试试这个:

@Component
public class MyIntegrator {

     @Autowired
     private MyListener listener;

     ...
}

然后听众没有自动装配.

首先,使用Spring必须要做的事情感觉不对new MyListener().我希望能够将其定义为自动连接的依赖项,并让Spring为我创建一个单例.我的问题是:

在新的Integrator接口中使用依赖注入的最佳方法是什么？集成器用于构建SessionFactory,因此当他们被要求集成自己时,我猜没有可用的应用程序上下文.因此,我在Integrator中需要的任何bean都需要以"老式"方式创建,并且不会在它们上接收自动装配.

我对Spring这个世界很陌生,你会说这是我应该期待看到的吗？我知道当我在SessionFactory时,我处于应用程序的不同范围,但是有没有办法获得对bean的引用并启用autowire,即使我是通过它创建它new？

我想出的解决方案ApplicationContextAware.这意味着每当上下文可用时都会MyListener收到对引用的引用ApplicationContext,并且我在方法调用的上下文中引用了bean,而不是bean构造.创建一个bean new并不限制它,所以Spring仍然给我应用程序上下文:

@Component
public class MyListener implements PostInsertEventListener, ApplicationContextAware {

    private static ApplicationContext context;

    public void onPostInsert(PostInsertEvent event) {
         // getDependent() == correct!
    }

    public void setApplicationContext(ApplicationContext context) throws BeanException {
        this.context = context;
    }

    public Dependent getDependent() {
        return context.getBean(Dependent.class);
    }

}

有没有更好的办法？

Answer 1

正如评论中所述,我采用了另一种集成Spring托管的HibernateEventListeners的方法.这是代码:

Spring托管的Hibernate事件侦听器的标识符接口:

public interface HibernateEventListener { }

HibernateIntegrator:

@Service
public class HibernateSpringIntegrator {

    private static final Logger log = LoggerFactory.getLogger(HibernateSpringIntegrator.class);

    @Autowired
    private HibernateEntityManagerFactory entityManagerFactory;

    @Autowired
    private HibernateSpringIntegratorRegistry hibernateSpringIntegratorRegistry;

    @PostConstruct
    public void registerListeners() {
        log.debug("Registering Spring managed HibernateEventListeners");

        EventListenerRegistry listenerRegistry = ((SessionFactoryImpl) entityManagerFactory
                .getSessionFactory()).getServiceRegistry().getService(
                EventListenerRegistry.class);
        List<HibernateEventListener> eventListeners = hibernateSpringIntegratorRegistry
                .getHibernateEventListeners();
        for (HibernateEventListener hel : eventListeners) {
            log.debug("Registering: {}", hel.getClass());
            if (PreInsertEventListener.class.isAssignableFrom(hel.getClass())) {
                listenerRegistry.appendListeners(EventType.PRE_INSERT,
                        (PreInsertEventListener) hel);
            }
            if (PreUpdateEventListener.class.isAssignableFrom(hel.getClass())) {
                listenerRegistry.appendListeners(EventType.PRE_UPDATE,
                        (PreUpdateEventListener) hel);
            }
            if (PreDeleteEventListener.class.isAssignableFrom(hel.getClass())) {
                listenerRegistry.appendListeners(EventType.PRE_DELETE,
                        (PreDeleteEventListener) hel);
            }
            if (PostInsertEventListener.class.isAssignableFrom(hel.getClass())) {
                listenerRegistry.appendListeners(EventType.POST_INSERT,
                        (PostInsertEventListener) hel);
            }
            if (PostUpdateEventListener.class.isAssignableFrom(hel.getClass())) {
                listenerRegistry.appendListeners(EventType.POST_UPDATE,
                        (PostUpdateEventListener) hel);
            }
            if (PostDeleteEventListener.class.isAssignableFrom(hel.getClass())) {
                listenerRegistry.appendListeners(EventType.POST_DELETE,
                        (PostDeleteEventListener) hel);
            }
            // Currently we do not need other types of eventListeners. Else this method needs to be extended.
        }
    }
}

"登记处":

@Component
public class HibernateSpringIntegratorRegistry {

    @Autowired(required = false)
    private List<HibernateEventListener> hibernateEventListeners;

    public List<HibernateEventListener> getHibernateEventListeners() {
        if (hibernateEventListeners == null) {
            return Collections.emptyList();
        }
        return hibernateEventListeners;
    }
}

这是一个示例实现:

@Component
public class MailGenerationEventListener implements HibernateEventListener, 
    PostDeleteEventListener, PostInsertEventListener, PostUpdateEventListener {

    @Override
    public void onPostDelete(PostDeleteEvent event) {
        Class<?> entityClass = event.getEntity().getClass();
        ...
    }

    @Override
    public void onPostInsert(PostInsertEvent event) {
        Class<?> entityClass = event.getEntity().getClass();
        ...
    }

    @Override
    public void onPostUpdate(PostUpdateEvent event) {
        Class<?> entityClass = event.getEntity().getClass();
        ...
    }
}