Jaxb 使用StreamSource读取XML文件时出现NullPointerException

我想从中间解析一个XML，离开根节点，从第二个节点开始处理。我写的代码是

    JAXBContent jaxbContext = JAXBContext.newInstance(new Class[]{Src.Fapmgr_Diag_Summary.class});
    XMLInputFactory xif = XMLInputFactory.newFactory();
    StreamSource xml_reader = new StreamSource("C:/Users/Ner/Desktop/Analysis/FAPMgrDiagnosticsSummary_apply_20140723112656.xml");
    XMLStreamReader xsr = xif.createXMLStreamReader(xml_reader);
    System.out.println(xsr.nextTag);       

但是我得到了NullpointerException。变量-xml_reader包含NULL，因为它可能无法读取xml。怎么了？有没有提到文件位置的错误方法

stacktrace错误为

    java.lang.NullPointerException
at javax.xml.stream.util.StreamReaderDelegate.nextTag(StreamReaderDelegate.java:66)
at oracle.ERP.Cloud.model.Module.AppModuleAMImpl.ParseXML(AppModuleAMImpl.java:76)
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 oracle.adf.model.binding.DCInvokeMethod.invokeMethod(DCInvokeMethod.java:638)
at oracle.adf.model.binding.DCDataControl.invokeMethod(DCDataControl.java:2136)
at oracle.adf.model.bc4j.DCJboDataControl.invokeMethod(DCJboDataControl.java:3063)
at oracle.adf.model.binding.DCInvokeMethod.callMethod(DCInvokeMethod.java:261)
at oracle.jbo.uicli.binding.JUCtrlActionBinding.doIt(JUCtrlActionBinding.java:1635)
at oracle.adf.model.binding.DCDataControl.invokeOperation(DCDataControl.java:2143)
at oracle.jbo.uicli.binding.JUCtrlActionBinding.invoke(JUCtrlActionBinding.java:740)
at oracle.adf.controller.v2.lifecycle.PageLifecycleImpl.executeEvent(PageLifecycleImpl.java:394)
at oracle.adfinternal.view.faces.model.binding.FacesCtrlActionBinding._execute(FacesCtrlActionBinding.java:252)
at oracle.adfinternal.view.faces.model.binding.FacesCtrlActionBinding.execute(FacesCtrlActionBinding.java:210)
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 com.sun.el.parser.AstValue.invoke(Unknown Source)
at com.sun.el.MethodExpressionImpl.invoke(Unknown Source)
at oracle.adf.controller.internal.util.ELInterfaceImpl.invokeMethod(ELInterfaceImpl.java:168)
at oracle.adfinternal.controller.activity.MethodCallActivityLogic.execute(MethodCallActivityLogic.java:160)
at oracle.adfinternal.controller.engine.ControlFlowEngine.executeActivity(ControlFlowEngine.java:989)
at oracle.adfinternal.controller.engine.ControlFlowEngine.doRouting(ControlFlowEngine.java:878)
at oracle.adfinternal.controller.engine.ControlFlowEngine.doRouting(ControlFlowEngine.java:777)
at oracle.adfinternal.controller.engine.ControlFlowEngine.invokeTaskFlow(ControlFlowEngine.java:242)
at oracle.adfinternal.controller.state.ChildViewPortContextImpl.invokeTaskFlow(ChildViewPortContextImpl.java:104)
at oracle.adfinternal.controller.state.ControllerState.createChildViewPort(ControllerState.java:1351)
at oracle.adfinternal.controller.ControllerContextImpl.createChildViewPort(ControllerContextImpl.java:78)
at oracle.adf.controller.internal.binding.DCTaskFlowBinding.createRegionViewPortContext(DCTaskFlowBinding.java:429)
at oracle.adf.controller.internal.binding.DCTaskFlowBinding.getViewPort(DCTaskFlowBinding.java:352)
at oracle.adf.controller.internal.binding.TaskFlowRegionModel.doProcessBeginRegion(TaskFlowRegionModel.java:160)
at oracle.adf.controller.internal.binding.TaskFlowRegionModel.processBeginRegion(TaskFlowRegionModel.java:108)
at oracle.adf.view.rich.component.fragment.UIXRegion$RegionContextChange.doChangeImpl(UIXRegion.java:1199)
at oracle.adf.view.rich.context.DoableContextChange.doChange(DoableContextChange.java:91)
at oracle.adf.view.rich.component.fragment.UIXRegion._beginInterruptibleRegion(UIXRegion.java:693)
at oracle.adf.view.rich.component.fragment.UIXRegion.processRegion(UIXRegion.java:498)
at oracle.adfinternal.view.faces.taglib.region.RegionTag.doStartTag(RegionTag.java:127)
at jsp_servlet.__mainflow_jspx._jspx___tag3(__mainflow_jspx.java:243)
at jsp_servlet.__mainflow_jspx._jspx___tag2(__mainflow_jspx.java:204)
at jsp_servlet.__mainflow_jspx._jspx___tag1(__mainflow_jspx.java:154)
at jsp_servlet.__mainflow_jspx._jspx___tag0(__mainflow_jspx.java:104)
at jsp_servlet.__mainflow_jspx._jspService(__mainflow_jspx.java:65)
at weblogic.servlet.jsp.JspBase.service(JspBase.java:34)
at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:227)
at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:125)
at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:300)
at weblogic.servlet.internal.ServletStubImpl.onAddToMapException(ServletStubImpl.java:416)
at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:326)
at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:183)
at weblogic.servlet.internal.RequestDispatcherImpl.invokeServlet(RequestDispatcherImpl.java:523)
at weblogic.servlet.internal.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:253)
at com.sun.faces.context.ExternalContextImpl.dispatch(ExternalContextImpl.java:410)
at org.apache.myfaces.trinidad.context.ExternalContextDecorator.dispatch(ExternalContextDecorator.java:44)
at org.apache.myfaces.trinidad.context.ExternalContextDecorator.dispatch(ExternalContextDecorator.java:44)
at oracle.adfinternal.view.faces.config.rich.RecordRequestAttributesDuringDispatch.dispatch(RecordRequestAttributesDuringDispatch.java:44)
at org.apache.myfaces.trinidad.context.ExternalContextDecorator.dispatch(ExternalContextDecorator.java:44)
at org.apache.myfaces.trinidad.context.ExternalContextDecorator.dispatch(ExternalContextDecorator.java:44)
at org.apache.myfaces.trinidad.context.ExternalContextDecorator.dispatch(ExternalContextDecorator.java:44)
at org.apache.myfaces.trinidadinternal.context.FacesContextFactoryImpl$OverrideDispatch.dispatch(FacesContextFactoryImpl.java:267)
at com.sun.faces.application.ViewHandlerImpl.executePageToBuildView(ViewHandlerImpl.java:469)
at com.sun.faces.application.ViewHandlerImpl.renderView(ViewHandlerImpl.java:140)
at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:189)
at org.apache.myfaces.trinidadinternal.application.ViewHandlerImpl.renderView(ViewHandlerImpl.java:193)
at oracle.adfinternal.view.faces.lifecycle.LifecycleImpl._renderResponse(LifecycleImpl.java:777)
at oracle.adfinternal.view.faces.lifecycle.LifecycleImpl._executePhase(LifecycleImpl.java:293)
at oracle.adfinternal.view.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:213)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:266)
at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:227)
at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:125)
at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:300)
at weblogic.servlet.internal.TailFilter.doFilter(TailFilter.java:26)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)
at oracle.adf.model.servlet.ADFBindingFilter.doFilter(ADFBindingFilter.java:205)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)
at oracle.adfinternal.view.faces.webapp.rich.RegistrationFilter.doFilter(RegistrationFilter.java:106)
at org.apache.myfaces.trinidadinternal.webapp.TrinidadFilterImpl$FilterListChain.doFilter(TrinidadFilterImpl.java:446)
at oracle.adfinternal.view.faces.activedata.AdsFilter.doFilter(AdsFilter.java:60)
at org.apache.myfaces.trinidadinternal.webapp.TrinidadFilterImpl$FilterListChain.doFilter(TrinidadFilterImpl.java:446)
at org.apache.myfaces.trinidadinternal.webapp.TrinidadFilterImpl._doFilterImpl(TrinidadFilterImpl.java:271)
at org.apache.myfaces.trinidadinternal.webapp.TrinidadFilterImpl.doFilter(TrinidadFilterImpl.java:177)
at org.apache.myfaces.trinidad.webapp.TrinidadFilter.doFilter(TrinidadFilter.java:92)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)
at oracle.security.jps.ee.http.JpsAbsFilter$1.run(JpsAbsFilter.java:111)
at java.security.AccessController.doPrivileged(Native Method)
at oracle.security.jps.util.JpsSubject.doAsPrivileged(JpsSubject.java:313)
at oracle.security.jps.ee.util.JpsPlatformUtil.runJaasMode(JpsPlatformUtil.java:413)
at oracle.security.jps.ee.http.JpsAbsFilter.runJaasMode(JpsAbsFilter.java:94)
at oracle.security.jps.ee.http.JpsAbsFilter.doFilter(JpsAbsFilter.java:161)
at oracle.security.jps.ee.http.JpsFilter.doFilter(JpsFilter.java:71)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)
at oracle.dms.servlet.DMSServletFilter.doFilter(DMSServletFilter.java:136)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)
at weblogic.servlet.internal.RequestEventsFilter.doFilter(RequestEventsFilter.java:27)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:56)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.wrapRun(WebAppServletContext.java:3715)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:3681)
at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:120)
at weblogic.servlet.internal.WebAppServletContext.securedExecute(WebAppServletContext.java:2277)
at weblogic.servlet.internal.WebAppServletContext.execute(WebAppServletContext.java:2183)
at weblogic.servlet.internal.ServletRequestImpl.run(ServletRequestImpl.java:1454)
at weblogic.work.ExecuteThread.execute(ExecuteThread.java:207)
at weblogic.work.ExecuteThread.run(ExecuteThread.java:176)

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请帮帮我。

首先尝试使用Java文件API读取中的文件，以确保路径正确。变量xml\u reader将不会为空。如果构造函数抛出异常，它将根本不在作用域中，或者它将是一个非null引用。新运算符从不返回null。你到底看到了什么？堆栈跟踪是什么样子的？此外，您发布的代码不会编译，因为nextTag是一个方法，而不是一个字段。这让我想知道，你的真实代码还有什么地方与你发布的不一样。我在调试变量xml_reader时看到它为空。最初，当我尝试使用createXMLStreamReader xsr=xif.CreateXmlStreamReaderNewFileInputStreamC解析相同的xml时：\\Users\\Ner\\Desktop\\Analysis\\FAPMgrDiagnosticsSummary\u apply\u 20140723112656.xml，它成功了。现在，由于xml内容已经更改，并且我不需要解析整个xml，所以我使用的StreamSource失败了。