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From "Andy Dailey" <Andy.Dai...@Haworth.com>
Subject RE: NullPointerException, how to determine cause?
Date Wed, 19 Jan 2005 18:01:58 GMT
Stack trace will give the line numbers if you compile with debug="on" in
the ant javac task command or javac -g <files> if command line
compiling.

 


> -----Original Message-----
> From: Alex Kravets [mailto:akravets@kligerweiss.com] 
> Sent: Wednesday, January 19, 2005 12:47 PM
> To: Struts Users Mailing List
> Subject: Re: NullPointerException, how to determine cause?
> 
> 
> I am sure this part works, because if comment out try block 
> everything 
> works fine. But If the cause of exception is the code in try 
> block, how 
> come catch does not work?
> 
> Pavel Kolesnikov wrote:
> 
> >I guess the only plase where NPE may occure is the line:
> >
> >         String sqlQuery = ((ExecuteQueryForm) form).getSQLQuery();
> >
> >Are you sure there's a form definition available for this action? It 
> >means, is there a "name" attribute defined in an appropriate 
> <action> 
> >element in your struts-config.xml?
> >
> >Pavel
> >
> >On Wed, 19 Jan 2005 12:34:51 -0500, Alex Kravets 
> ><akravets@kligerweiss.com> wrote:
> >  
> >
> >>I am trying to connect to a database in Action Class and set return 
> >>data into a vector. Then vector is set into session and session is 
> >>read from forwarded page. However, I am getting 
> NullPointerException. 
> >>Now I put the part of the code that I think might generate an 
> >>exception into try block, but no luck same exception. In addition, 
> >>stack trace does not seem to give the line of perform() where error 
> >>occurs.
> >>
> >>SEVERE: Servlet.service() for servlet action threw exception 
> >>java.lang.NullPointerException
> >>        at app.ExecuteQueryAction.perform(Unknown Source)
> >>        at
> >>org.apache.struts.action.ActionServlet.processActionPerform(
> ActionServlet.java:1787)
> >>        at
> >>org.apache.struts.action.ActionServlet.process(ActionServlet
> .java:1586)
> >>        at
> >>org.apache.struts.action.ActionServlet.doPost(ActionServlet.
> java:510)
> >>        at 
> javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
> >>        at 
> javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
> >>        at
> >>org.apache.catalina.core.ApplicationFilterChain.internalDoFi
> lter(ApplicationFilterChain.java:237)
> >>        at
> >>org.apache.catalina.core.ApplicationFilterChain.doFilter(App
> licationFilterChain.java:157)
> >>        at
> >>org.apache.catalina.core.StandardWrapperValve.invoke(Standar
> dWrapperValve.java:214)
> >>        at
> >>org.apache.catalina.core.StandardContextValve.invoke(Standar
> dContextValve.java:178)
> >>        at
> >>org.apache.catalina.core.StandardHostValve.invoke(StandardHo
> stValve.java:126)
> >>        at
> >>org.apache.catalina.valves.ErrorReportValve.invoke(ErrorRepo
> rtValve.java:105)
> >>        at
> >>org.apache.catalina.core.StandardEngineValve.invoke(Standard
> EngineValve.java:107)
> >>        at
> >>org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAd
> apter.java:148)
> >>        at
> >>org.apache.coyote.http11.Http11Processor.process(Http11Proce
> ssor.java:825)
> >>        at
> >>org.apache.coyote.http11.Http11Protocol$Http11ConnectionHand
> ler.processConnection(Http11Protocol.java:731)
> >>        at
> >>org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(Poo
> lTcpEndpoint.java:526)
> >>        at
> >>org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(
LeaderFollowerWorkerThread.java:80)
> >>        at
> >>org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.ru
> n(ThreadPool.java:684)
> >>        at java.lang.Thread.run(Thread.java:595)
> >>
> >>and Action Class:
> >>
> >>package app;
> >>
> >>import java.io.IOException;
> >>import java.util.Vector;
> >>import javax.servlet.ServletException;
> >>import javax.servlet.http.HttpServletRequest;
> >>import javax.servlet.http.HttpSession;
> >>import javax.servlet.http.HttpServletResponse;
> >>import org.apache.struts.action.Action;
> >>import org.apache.struts.action.ActionError;
> >>import org.apache.struts.action.ActionErrors;
> >>import org.apache.struts.action.ActionForm;
> >>import org.apache.struts.action.ActionForward;
> >>import org.apache.struts.action.ActionMapping;
> >>import org.apache.struts.action.ActionServlet;
> >>import com.kwi.DBDriver;
> >>
> >>public final class ExecuteQueryAction extends Action {
> >>
> >>    public ActionForward perform(ActionMapping mapping,
> >>            ActionForm form,
> >>            HttpServletRequest request,
> >>            HttpServletResponse response)
> >>        throws IOException, ServletException {
> >>
> >>        // Obtain username and password from web tier
> >>        String sqlQuery = ((ExecuteQueryForm) form).getSQLQuery();
> >>        Vector v = new Vector();
> >>        HttpSession session = request.getSession();
> >>        try{
> >>                v = DBDriver.doSelect("generic2",sqlQuery);
> >>                v.add("test");
> >>                session.setAttribute("output",v);
> >>        }
> >>        catch(NullPointerException nle){
> >>                v.add("no good");
> >>                session.setAttribute("output",v);
> >>        }
> >>        session.setAttribute("query",form);
> >>
> >>        // Return success
> >>        return mapping.findForward("success");
> >>
> >>    }
> >>
> >>} // End LogonAction
> >>
> >>thanks,
> >>Alex
> >>
> >>------------------------------------------------------------
> ---------
> >>To unsubscribe, e-mail: user-unsubscribe@struts.apache.org
> >>For additional commands, e-mail: user-help@struts.apache.org
> >>
> >>
> >>    
> >>
> >
> >---------------------------------------------------------------------
> >To unsubscribe, e-mail: user-unsubscribe@struts.apache.org
> >For additional commands, e-mail: user-help@struts.apache.org
> >
> >
> >  
> >
> 

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