Java 休眠错误:session.get()
我在我的NetBeans项目中使用Hibernate,当我尝试使用以下代码从Oracle数据库获取结果集时:Java 休眠错误:session.get(),java,oracle,hibernate,session,get,Java,Oracle,Hibernate,Session,Get,我在我的NetBeans项目中使用Hibernate,当我尝试使用以下代码从Oracle数据库获取结果集时: Client c = (Client) session.get(Client.class, id); 我得到以下错误: javax.faces.el.EvaluationException: java.lang.NullPointerException at javax.faces.component.MethodBindingMethodExpressionAdapter.i
Client c = (Client) session.get(Client.class, id);
我得到以下错误:
javax.faces.el.EvaluationException: java.lang.NullPointerException
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:101)
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
at javax.faces.component.UICommand.broadcast(UICommand.java:315)
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282)
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:744)
Caused by: java.lang.NullPointerException
at mb.MBObavestenje.pronadjiKlijenta(MBObavestenje.java:118)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.el.parser.AstValue.invoke(AstValue.java:278)
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:273)
at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87)
... 28 more
当我尝试使用此对象c.toString()时,会出现空指针异常
似乎.get()函数不会返回客户端类的对象。我已经为这个问题挣扎了3天了,有人能帮我吗
第118行中的代码引用ManagedBean,它表示:
System.out.println(c.getName());
以下是有问题的方法:
public CLient getClient(String id){
Session session = HibernateUtil.getSessionFactory().openSession();
session.beginTransaction();
Client c = (Client) session.get(Client.class, id);
session.getTransaction().commit();
return c;
}
还有,当我试着
System.out.println(c.getName())
方法提交后,它还报告了NullPointerException。MBObavestenje.java第118行的代码行是什么?显示相关代码。这是ManagedBean中的一行,我试图从对象c获取信息:System.out.println(c.getName());在问题中张贴相关代码。不是在评论中。从您发布的一行代码中我们可以说,异常是由
c
为null引起的。因此,要么您以前没有调用过session.get(),要么您调用了session.get(),但其ID在数据库中不存在,要么某些代码在调用后将c重置为null。但是没有代码,我们只能猜测。使用调试器。我用代码更新了问题,你现在可以看一下吗?MBObavestenje.java第118行的代码是什么?显示相关代码。这是ManagedBean中的一行,我试图从对象c获取信息:System.out.println(c.getName());在问题中张贴相关代码。不是在评论中。从您发布的一行代码中我们可以说,异常是由c
为null引起的。因此,要么您以前没有调用过session.get(),要么您调用了session.get(),但其ID在数据库中不存在,要么某些代码在调用后将c重置为null。但是没有代码,我们只能猜测。使用你的调试器。我用代码更新了问题,你现在可以看一下吗?