problem when doing callback

[Krthekeyan Suryanarayanan <kr...@verchaska.com>]

Hi all,

can u guys help me in working out the following scenerio.

exception
***************
ApplicationRunTime Exception
**************************************
unable to invoke the listener method when it is performing callback ..


.page entries
*****************
    <property-specification name="callback" 
type="org.apache.tapestry.callback.PageCallback" persistent="yes"/>



I have a MyPage which extend BasePage

public abstract PageCallback getCallback();
public abstract void setCallback(PageCallback value);


formSubmit(IRequestCycle cycle)
{
PageCallback pagecallback = getCallback();
 try
    {
  // somecondition
    }catch(Exception e)
{
     pagecallback.performCallback(cycle);
}
}

what could be the solution.

thanks,
krthekeyan.s


Actual error pasted
*********************
org.apache.tapestry.ApplicationRuntimeException
***********************************************************
Unable to invoke method selectToppings on 
com.vtech.research.tapestry.components.demo.checkbox.delegator.SelectedCheckBox$Enhance_35@1909385[SelectedCheckBox]: 
null

java.lang.NullPointerException
***********************************
Stack Trace:
com.vtech.research.tapestry.components.demo.checkbox.delegator.SelectedCheckBox.selectToppings(SelectedCheckBox.java:85) 
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) 
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) 
java.lang.reflect.Method.invoke(Method.java:324) 
org.apache.tapestry.listener.ListenerMap.invokeTargetMethod(ListenerMap.java:301) 
org.apache.tapestry.listener.ListenerMap.access$100(ListenerMap.java:87) 
org.apache.tapestry.listener.ListenerMap$SyntheticListener.invoke(ListenerMap.java:141) 
org.apache.tapestry.listener.ListenerMap$SyntheticListener.actionTriggered(ListenerMap.java:146) 
org.apache.tapestry.form.Form.renderComponent(Form.java:457) 
org.apache.tapestry.AbstractComponent.render(AbstractComponent.java:880) 
org.apache.tapestry.form.Form.rewind(Form.java:602) 
org.apache.tapestry.engine.RequestCycle.rewindForm(RequestCycle.java:475) 
org.apache.tapestry.form.Form.trigger(Form.java:616) 
org.apache.tapestry.engine.DirectService.service(DirectService.java:210) 
org.apache.tapestry.engine.AbstractEngine.service(AbstractEngine.java:912) 
org.apache.tapestry.ApplicationServlet.doService(ApplicationServlet.java:238) 
org.apache.tapestry.ApplicationServlet.doPost(ApplicationServlet.java:367) 
javax.servlet.http.HttpServlet.service(HttpServlet.java:760) 
javax.servlet.http.HttpServlet.service(HttpServlet.java:853) 
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247) 
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193) 
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256) 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643) 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480) 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995) 
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643) 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480) 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995) 
org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2417) 
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180) 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643) 
org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171) 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641) 
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172) 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641) 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480) 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995) 
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174) 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643) 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480) 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995) 
org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:193) 
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:781) 
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:549) 
org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:589) 
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:666) 
java.lang.Thread.run(Thread.java:534) 



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