java.lang.NullPointerException bei org.apache.jsp.WEB_002dINF.view.profilEtudiant_jsp._jspService

Question

Ich kann meinen Code nicht arbeiten, der einzige Hinweis, den ich habe, ist die Warnung über unkontrollierte Besetzung, aber es scheint mir, dass ich kann nicht genauer sein ....

ich habe versucht, in der <% %> die @SuppressWarnings (value="unchecked") gerade über meinen Code zu setzen, aber es hat nicht funktioniert ...

Hier ist das Fehlerprotokoll:

juin 22, 2016 4:25:34 AM org.apache.catalina.core.StandardWrapperValve invoke 
GRAVE: Servlet.service() for servlet [GroupeEleve] in context with path [/GAPP2] threw exception [ 
An exception occurred processing JSP page /WEB-INF/view/profilEtudiant.jsp at line 668 

665:  <tr> 
666:  <% 
667:   Users U = (Users)session.getAttribute("user"); 
668:   Set<Absences> A=(Set<Absences>)U.getAbsenceses(); 
669   List<Absences> B = new ArrayList<Absences>(A); 
670:   for(int i=0;i<B.size();i++){%> 
671:    <td><%out.print(B.get(i).getDate()) ;%></td> 


Stacktrace:] with root cause 
java.lang.NullPointerException 
    at org.apache.jsp.WEB_002dINF.view.profilEtudiant_jsp._jspService(profilEtudiant_jsp.java:817) 
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731) 
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:439) 
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395) 
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731) 
    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.ApplicationDispatcher.invoke(ApplicationDispatcher.java:747) 
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:485) 
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:410) 
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:337) 
    at com.isep.controlleurs.GroupeEleve.doGet(GroupeEleve.java:46) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:624) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731) 
    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:505) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169) 
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103) 
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956) 
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:436) 
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1078) 
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625) 
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316) 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) 
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) 
    at java.lang.Thread.run(Unknown Source) 

Answer 1

Möglicherweise ist Ihre Sitzung nicht Benutzer Attribut.Bitte überprüfen Sie Ihre ses sion user.if Wenn der Benutzer nicht null ist, kann U.getAbcenceses() den Wert null zurückgeben, und Set A erhält den Wert null.So, wenn Sie den Wert von A bis B zuweisen und B.get (i) .getDate () wird eine Nullzeiger-Ausnahme verursachen.