Hibernate Session关闭问题!

Question

下面的函数是我的网络应用程序中按钮的actionListener，我正在从数据库的表中删除旧选择的行并将新行插入数据库。

public void getSelectedExemptionItems(ActionEvent ae) {
        Session hibernateSession;
        Session hibernate2Session;
        selectedExemptions = new ArrayList<ExemptionBean>();
        for (ExemptionBean eBean : exemBean) { // iterating over the list of ExemptionBean class
            if (selectedExemptionIDs.get(eBean.getExemptionID()).booleanValue()) {
                selectedExemptions.add(eBean); // adding every ExemptionBean that is selected.
            }
        }
        // getting importane session variables
        SessionBean1 theSessionBean = (SessionBean1) FacesContext.getCurrentInstance().getExternalContext().getSessionMap().get("SessionBean1");
        JAdmApplication admApplication = theSessionBean.getAdmApplication();
        long admAppID = admApplication.getJAdmApplicationId();
//        ArrayList<JAdmAppExemption> admAppExemption = (ArrayList<JAdmAppExemption>)theSessionBean.getAdmAppExemption();

        JAdmAppExemption admAppExem = new JAdmAppExemption();

        // try catch : delete all previously chosen exemptions from database by logged-in user.
        try {
            hibernateSession = HibernateUtil.getAdmSessionFactory().getCurrentSession();
            Transaction t = hibernateSession.beginTransaction();
            t.begin();
            String sequel = "DELETE FROM JAdmAppExemption WHERE createdby = ?";
            Query q = hibernateSession.createQuery(sequel);
            q.setParameter(0, theSessionBean.getPortalUserId());

        } catch (Exception e){
            System.out.println("Row could not be deledted from database!!");
        }

//         adding all selected exemptions to the database

        for (ExemptionBean e : selectedExemptions) {
            admAppExem.setAdClientId(1000001);
            admAppExem.setAdOrgId(1000001);
            admAppExem.setCreated(getTimestamp());
            admAppExem.setCreatedby(theSessionBean.getPortalUserId());
            admAppExem.setIsactive('Y');
            admAppExem.setJAdmAppExemptionId(getJAdmAppExemptionIdSequence());
            admAppExem.setJAdmApplicationId(admAppID);
            admAppExem.setJAdmExemptionId(e.getExemptionID());
            admAppExem.setUpdated(getTimestamp());
            admAppExem.setUpdatedby(theSessionBean.getPortalUserId());

            hibernate2Session = HibernateUtil.getAdmSessionFactory().getCurrentSession(); // session is opened here!
            Transaction tx = hibernate2Session.beginTransaction();
            tx.begin();
            try {
                hibernate2Session.beginTransaction();
                hibernate2Session.save(admAppExem); // is it save or saveOrUpdate??
                hibernate2Session.getTransaction().commit();
                updateJAdmAppExemptionIdSequence();

            } catch (Throwable ex){
                if (hibernate2Session.getTransaction().isActive()) {
                    hibernate2Session.getTransaction().rollback();
                }
                ex.printStackTrace();
            }
        }
    }

我不断收到异常: session 已关闭!有人可以解释一下 hibernate 中 session 是如何关闭的(自动？)以及如何使用它们..

这是异常的详细堆栈跟踪:

javax.faces.FacesException: org.hibernate.SessionException: Session is closed!
        at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:90)
        at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:100)
        at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
        at com.icesoft.faces.webapp.http.core.JsfLifecycleExecutor.apply(JsfLifecycleExecutor.java:18)
        at com.icesoft.faces.webapp.http.core.ReceiveSendUpdates.renderCycle(ReceiveSendUpdates.java:132)
        at com.icesoft.faces.webapp.http.core.ReceiveSendUpdates.service(ReceiveSendUpdates.java:74)
        at com.icesoft.faces.webapp.http.core.RequestVerifier.service(RequestVerifier.java:31)
        at com.icesoft.faces.webapp.http.common.standard.PathDispatcherServer.service(PathDispatcherServer.java:24)
        at com.icesoft.faces.webapp.http.servlet.BasicAdaptingServlet.service(BasicAdaptingServlet.java:16)
        at com.icesoft.faces.webapp.http.servlet.PathDispatcher.service(PathDispatcher.java:23)
        at com.icesoft.faces.webapp.http.servlet.SessionDispatcher.service(SessionDispatcher.java:53)
        at com.icesoft.faces.webapp.http.servlet.SessionVerifier.service(SessionVerifier.java:26)
        at com.icesoft.faces.webapp.http.servlet.PathDispatcher.service(PathDispatcher.java:23)
        at com.icesoft.faces.webapp.http.servlet.MainServlet.service(MainServlet.java:131)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at com.icesoft.faces.webapp.xmlhttp.BlockingServlet.service(BlockingServlet.java:56)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
        at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:857)
        at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:565)
        at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1509)
        at java.lang.Thread.run(Thread.java:619)
Caused by: javax.faces.el.EvaluationException: org.hibernate.SessionException: Session is closed!
        at com.sun.faces.application.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:102)
        at javax.faces.component.UICommand.broadcast(UICommand.java:380)
        at com.icesoft.faces.component.panelseries.UISeries$RowEvent.broadcast(UISeries.java:617)
        at com.icesoft.faces.component.panelseries.UISeries.broadcast(UISeries.java:285)
        at com.icesoft.faces.component.paneltabset.PanelTabSet.broadcast(PanelTabSet.java:320)
        at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:475)
        at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:756)
        at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:82)
        ... 27 more
Caused by: org.hibernate.SessionException: Session is closed!
        at org.hibernate.impl.AbstractSessionImpl.errorIfClosed(AbstractSessionImpl.java:49)
        at org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1319)
        at sun.reflect.GeneratedMethodAccessor2480.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:301)
        at $Proxy233.beginTransaction(Unknown Source)
        at univportal.AdmissionApplication.Application.getSelectedExemptionItems(Application.java:1595)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.el.parser.AstValue.invoke(AstValue.java:172)
        at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:276)
        at com.sun.faces.application.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88)
        ... 34 more

谢谢

Answer 1

这是我对此问题找到的简明答案 here如果有人在 Hibernate 中遇到这个问题。显然这很简单!

在 hibernate 中使用托管 session 来简化单元测试 06nov06

如果您曾经尝试在 Hibernate 中重用 session ，您可能会遇到此异常...

org.hibernate.SessionException: Session is closed!
   at org.hibernate.impl.AbstractSessionImpl.errorIfClosed(AbstractSessionImpl.java:49)
   at org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1319)
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
   at java.lang.reflect.Method.invoke(Unknown Source)
   at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:301)
   at $Proxy0.beginTransaction(Unknown Source)
   ....

原因是 Hibernate 使用线程管理 session 。通过这种类型的 session 管理，Hibernate 可以为您管理 session 。当您第一次尝试使用 session 时，Hibernate 将创建一个 session 并将其附加到您的本地线程。当您在 session 中提交事务时，Hibernate 将自动关闭 session ，这意味着它无法重用。

要解决此问题，最好的选择是使用托管 session 。通过托管 session ，您可以完全控制创建、刷新、提交和关闭 session 。方法如下。

在您的 hibernate.cfg.xml 中，将属性 current_session_context_class 更改为 托管。

要创建 session 并在该 session 中启动事务，请执行以下操作...

org.hibernate.classic.Session session = HibernateUtil.getSessionFactory().openSession();
   session.setFlushMode(FlushMode.MANUAL);
   ManagedSessionContext.bind(session);
   session.beginTransaction();

要在 session 中提交一个事务，请执行以下操作...

ManagedSessionContext.unbind(HibernateUtil.getSessionFactory());
   session.flush();
   session.getTransaction().commit();
   session.close();

为了在单元测试中使用此代码，我创建了这个基本单元测试类，我的所有单元测试都扩展了它。每当我想创建一个新的 session 或事务时，我都会调用createNewSessionAndTransaction()方法。为了提交 session 的事务，我调用方法 commitTransaction()。

import org.hibernate.FlushMode;
import org.hibernate.Session;
import org.hibernate.context.ManagedSessionContext;
import util.HibernateUtil;
import junit.framework.TestCase;

/**
 * Abstract unit test with helper methods for managed session control
 */
public abstract class ManagedSessionUnitTest extends TestCase {

   /**
    * Create a new Session.
    *
    * For this method to work, the application managed session strategy has to
    * be enabled. This basically means that the life of a session is controlled
    * by you and and not by Hibernate.
    *
    * To enable the application managed session strategy set the property
    * hibernate.current_session_context_class to "managed".
    *
    * Within this method we create a new session and set the flush mode to
    * MANUAL. This ensures that we have full control over when the session is
    * flushed to the database.
    */
   protected org.hibernate.Session createNewSession() {
      org.hibernate.classic.Session session = HibernateUtil.getSessionFactory().openSession();
      session.setFlushMode(FlushMode.MANUAL);
      ManagedSessionContext.bind(session);
      return (org.hibernate.Session) session;
   }

   /**
    * Start a new Transaction in the given session
    * @param session The session to create the transaction in
    */
   protected void startNewTransaction(Session session) {
      session.beginTransaction();
   }

   /**
    * Shortcut method that creates a new session and begins a transaction in it
    * @return A new session with a transaction started
    */
   protected org.hibernate.Session createNewSessionAndTransaction() {
      Session session = createNewSession();
      startNewTransaction(session);
      return session;
   }

   /**
    * Commit the transaction within the given session. This method unbinds
    * the session from the session context (ManagedSessionContext), flushes
    * the session, commmits the session and then closes the session
    * @param session The session with the transaction to commit
    */
   protected void commitTransaction(Session session) {
      ManagedSessionContext.unbind(HibernateUtil.getSessionFactory());
      session.flush();
      session.getTransaction().commit();
      session.close();
   }

}