使用HK2向Jersey返回hibernate会话

时间：2015-08-07 23:46:20

标签： java hibernate dependency-injection jersey-2.0 hk2

我正在开发小应用程序并且在DI方面存在一些问题。

我有一个存储库类用于保存我注入到我的服务中的实体。我想使用H2K向它注入Session对象。 为此，我尝试执行以下SO帖子中描述的类似内容：

  1. Jersey + HK2 + Grizzly: Proper way to inject EntityManager?
  2. Using Jersey 2.0, how do you register a bindable instance per request?
  3. How do I properly configure an EntityManager in a jersey / hk2 application?

    4. 所以我创建了SFFactory类并在ApplicationConfig中注册它。

    SFFactory.java 

    import org.glassfish.hk2.api.Factory;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;

public class SFFactory implements Factory<Session> {

private SessionFactory factory;

public SFFactory() {
    Configuration configuration = new Configuration();
    configuration.configure("hibernate.cfg.xml");
    StandardServiceRegistryBuilder srBuilder = new StandardServiceRegistryBuilder();
    srBuilder.applySettings(configuration.getProperties());
    factory = configuration.buildSessionFactory(srBuilder.build());
    }

@Override
public Session provide() {
    return factory.openSession();
    }

@Override
public void dispose(Session session) {
    if (session.isOpen()) {
        session.close();
        }
    }
}

    ApplicationConfig.java 

    import org.alexdzot.phonettesttask.repository.MessageRepository;
import org.glassfish.hk2.utilities.binding.AbstractBinder;
import org.glassfish.jersey.server.ResourceConfig;
import org.hibernate.Session;

import javax.inject.Singleton;
import javax.ws.rs.ApplicationPath;

@ApplicationPath("/rest/*")
public class ApplicationConfig extends ResourceConfig {

public ApplicationConfig() {
    packages("org.alexdzot.phonettesttask");
    register(new AbstractBinder() {
        @Override
        protected void configure() {
            bindFactory(SFFactory.class).to(Session.class);
            bindFactory(MessageRepositoryFactory.class).to(MessageRepository.class).in(Singleton.class);
            }
        });
    }
}

    DefaultMessageRepository 

    import org.alexdzot.phonettesttask.model.Message;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.jvnet.hk2.annotations.Service;

import javax.inject.Inject;
import java.util.List;

@Service
public class DefaultMessageRepository implements MessageRepository {

@Inject
private Session session;

public void saveMessage(Message message) {
    Session session = null;
    Transaction tx = null;
    try {
        tx = session.beginTransaction();
        session.save(message);
        tx.commit();
        } catch (Exception e) {
        tx.rollback();
        } finally {
        session.close();
        }
    }

public List<Message> getAllMessages() {
    Session session = null;
    Transaction tx = null;
    List<Message> messages = null;
    try {
        tx = session.beginTransaction();
        messages = session.createCriteria(Message.class).list();

        } catch (Exception e) {
        tx.rollback();
        } finally {
        session.close();
        return messages;
        }
    }
}

    但是当我运行应用程序并尝试调用存储库方法时，我得到了NullPoinerException。我无法理解我做错了什么。 这就是Tomcat日志所说的：

    *08-Aug-2015 02:42:18.232 SEVERE [http-nio-8080-exec-10] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [org.alexdzot.phonettesttask.config.ApplicationConfig] in context with path [] threw exception [java.lang.NullPointerException] with root cause
 java.lang.NullPointerException
    at org.alexdzot.phonettesttask.repository.DefaultMessageRepository.getAllMessages(DefaultMessageRepository.java:42)
    at org.alexdzot.phonettesttask.service.MessageResource.viewSentMessages(MessageResource.java:38)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.glassfish.jersey.server.model.internal.ResourceMethodInvocationHandlerFactory$1.invoke(ResourceMethodInvocationHandlerFactory.java:81)
    at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher$1.run(AbstractJavaResourceMethodDispatcher.java:144)
    at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.invoke(AbstractJavaResourceMethodDispatcher.java:161)
    at org.glassfish.jersey.server.model.internal.JavaResourceMethodDispatcherProvider$TypeOutInvoker.doDispatch(JavaResourceMethodDispatcherProvider.java:205)
    at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.dispatch(AbstractJavaResourceMethodDispatcher.java:99)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:389)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:347)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:102)
    at org.glassfish.jersey.server.ServerRuntime$2.run(ServerRuntime.java:308)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:267)
    at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:317)
    at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:291)
    at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1140)
    at org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:403)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:386)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:334)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:221)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:617)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1521)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1478)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)*

    任何想法我的解决方案有什么问题以及导致该问题的原因是什么？

1 个答案:

答案 0 :(得分：5)

主要问题：

  

[java.lang.NullPointerException]

查看您的存储库类

@Service
public class DefaultMessageRepository implements MessageRepository {

    @Inject
    private Session session; <-------------------+
                                                 | // You shadow session
    public void saveMessage(Message message) {   |
        Session session = null;   <--------------+
        Transaction tx = null;
        try {
            tx = session.beginTransaction();
        ...
    }
    ...
}

您正在注入注入的字段session。所以你只是使用本地session，它是null。所以在你的方法中，只需摆脱Session session = null;。注入应该可以正常工作，您应该只能使用session字段。

另一个问题：

所有请求都使用相同的Session。由于DefaultMessagFactory是单身，HK2声称Session也应该是单身，因为它包含在单身中。因此，不是将SFFactory作为默认@PerLookup范围，而是获得一个单例工厂，因此只会创建一个Session。这不是您应该要的行为。您可以通过在工厂类中放置一些打印语句来测试它。

确保为每个请求创建新Session的一种方法是：

  1. 使用javax.inject.Provider<Session>，懒洋洋地加载会话，这将允许使用它来保持我们配置的范围。

    @Inject
private javax.inject.Provider<Session> session;

@Override
public void saveEvent(Event event) {
    Session s = session.get();
    Transaction tx = s.beginTransaction();

  2. 在请求范围中配置SFFactory 

    @Override
protected void configure() {
    bindFactory(SFFactory.class)
            .to(Session.class)
            .in(RequestScoped.class);
}

    3. 要解决的另一件事是SessionFactory应该是应用程序中的单个实例。为此，我们可以为它创建一个工厂，并将其注入SFFactory。例如

    public class SessionFactoryFactory implements Factory<SessionFactory> {

    private final SessionFactory factory;

    public SessionFactoryFactory() {
        Configuration configuration = new Configuration();
        configuration.configure("hibernate.cfg.xml");
        StandardServiceRegistryBuilder srBuilder = new StandardServiceRegistryBuilder();
        srBuilder.applySettings(configuration.getProperties());
        factory = configuration.buildSessionFactory(srBuilder.build());
        System.out.println("--- SessionFactory Created ---");
    }

    @Override
    public SessionFactory provide() {
        System.out.println("--- SessionFactory Provided ---");
        return factory;
    }

    @Override
    public void dispose(SessionFactory factory) {
        factory.close();
    }
}

    在SFFactory

    中 
    public class SFFactory implements Factory<Session> {

    private final SessionFactory factory;

    @Inject
    public SFFactory(SessionFactory factory) {
        this.factory = factory;
    }

    @Override
    public Session provide() {
        System.out.println("--- Session Created ---");
        return factory.openSession();
    }

    @Override
    public void dispose(Session session) {
        if (session.isOpen()) {
            session.close();
        }
    }
}

    您的配置会更改为

    @Override
protected void configure() {
    bindFactory(SessionFactoryFactory.class)
            .to(SessionFactory.class)
            .in(Singleton.class);
    bindFactory(SFFactory.class)
            .to(Session.class)
            .in(RequestScoped.class);
}

    更新

    所以除了阴影之外，另一个主要问题是OP没有显示的MessageRepositoryFactory（在评论的github项目中）。 

    public class MessageRepositoryFactory implements Factory<MessageRepository> {
    @Override
    public MessageRepository provider() {
        return new DefaultMessageRepository();
    }
    ...
}

    当您实例化自己的对象时，默认情况下，框架不会处理注入。这就是为什么注射Session没有发生的原因。

    您可以像这样绑定

    ，而不是像这样使用Factory 
    bind(DefaultMessageRepository.class).to(MessageRepository.class).in(..);

    这样框架就会创建实例。 Factory实际上只应该在无法绑定上述方式的地方使用，例如你有一些初始化要做。我们甚至可能没有为Factory创建SessionFactoryFactory，而是在其他地方完成了所有会话工厂配置，只是绑定了实例。例如

    SessionFactory sessionFactory =...
...
bind(sessionFactory).to(SessionFactory.class);

    我们只绑定一个SessionFactory单例。

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