CometServerPush problem

Question

asked 2014-02-24 12:39:03 +0800

Hi all! I had to use zk server push feature and i've done a stupid project, just to try. There's a poster of event on a queue and a receiver that "manage" the event.

poster.zul:

<window title="points generator" border="normal" width="100%"
    height="100%" apply="org.zkoss.bind.BindComposer"
    viewModel="@id('vm') @init('PosterVM')">

<button id="gen" label="post an event" onClick="@command('postEvent')" />

</window>

receiver.zul:

<window title="points generator" border="normal" width="100%"
    height="100%" apply="org.zkoss.bind.BindComposer"
    viewModel="@id('vm') @init('ReceiverVM')" onServerPush="@command('doServerPush')">

    <label value="@load(vm.label)"></label>

</window>

PosterVM.java:

public class PosterVM {

EventQueue<Event> eq = EventQueues.lookup("francis queue", EventQueues.APPLICATION, true);                           
@Command
public void postEvent(){
    eq.publish( new Event( "onStiCazzi" ) );    
}

}

ReceiverVM:

public class ReceiverVM {

private String label;
private EventQueue<Event> eq = EventQueues.lookup("francis queue", EventQueues.APPLICATION, true);

@Init
public void init(){
    label = "No points received";
    eq.subscribe( new FrancisEventListener<Event>() );

}

@Command
@NotifyChange("label")
public void doServerPush(@ContextParam(ContextType.TRIGGER_EVENT) Event evt){

    int ret = (int) evt.getData();
    label = "Point received: ".concat( Integer.toString(ret) );

}

}

FrancisEventListener.java:

public class FrancisEventListener<T extends Event> implements EventListener<Event>{

@Override
public void onEvent(Event event) throws Exception {

    try{
        Random r = new Random();
        Executions.getCurrent().postEvent(new Event("onServerPush", null, r.nextInt(100)));

    }
    catch (ClassCastException e){
        e.printStackTrace();
    }

}

}

Sometimes ( not always! ) when I restart tomcat I get this:

SEVERE:

java.lang.NullPointerException at org.zkoss.zkmax.ui.comet.CometAsyncServlet$AsyncInfo.complete(CometAsyncServlet.java:150) at org.zkoss.zkex.ui.comet.CometServerPush.cleanAsyncInfo(CometServerPush.java:340) at org.zkoss.zkex.ui.comet.CometServerPush.schedule(CometServerPush.java:229) at org.zkoss.zk.ui.impl.DesktopImpl.scheduleServerPush(DesktopImpl.java:1469) at org.zkoss.zk.ui.Executions.schedule(Executions.java:873) at org.zkoss.zk.ui.event.impl.ServerPushEventQueue$DesktopInfo.publish(ServerPushEventQueue.java:157) at org.zkoss.zk.ui.event.impl.ServerPushEventQueue$DesktopInfo.access$000(ServerPushEventQueue.java:137) at org.zkoss.zk.ui.event.impl.ServerPushEventQueue.publish(ServerPushEventQueue.java:53) at PosterVM.postEvent(PosterVM.java:11) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.zkoss.bind.impl.ParamCall.call(ParamCall.java:111) at org.zkoss.bind.impl.BinderImpl.doExecute(BinderImpl.java:1745) at org.zkoss.bind.impl.BinderImpl.doCommand(BinderImpl.java:1506) at org.zkoss.bind.impl.BinderImpl.access$1500(BinderImpl.java:107) at org.zkoss.bind.impl.BinderImpl$CommandEventListener.onEvent0(BinderImpl.java:1375) at org.zkoss.bind.impl.BinderImpl$CommandEventListener.onEvent(BinderImpl.java:1327) at org.zkoss.zk.ui.AbstractComponent.onEvent(AbstractComponent.java:2743) at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:2714) at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:2655) at org.zkoss.zk.ui.impl.EventProcessor.process(EventProcessor.java:136) at org.zkoss.zk.ui.impl.UiEngineImpl.processEvent(UiEngineImpl.java:1721) at org.zkoss.zk.ui.impl.UiEngineImpl.process(UiEngineImpl.java:1506) at org.zkoss.zk.ui.impl.UiEngineImpl.execUpdate(UiEngineImpl.java:1216) at org.zkoss.zk.au.http.DHtmlUpdateServlet.process(DHtmlUpdateServlet.java:601) at org.zkoss.zk.au.http.DHtmlUpdateServlet.doGet(DHtmlUpdateServlet.java:483) at org.zkoss.zk.au.http.DHtmlUpdateServlet.doPost(DHtmlUpdateServlet.java:492) at javax.servlet.http.HttpServlet.service(HttpServlet.java:641) at javax.servlet.http.HttpServlet.service(HttpServlet.java:722) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:395) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:250) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:166) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source)

feb 24, 2014 1:34:56 PM org.apache.catalina.core.StandardWrapperValve invoke SEVERE: Servlet.service() for servlet [CometAsyncServlet] in context with path [/ServerPush] threw exception java.lang.NullPointerException at org.zkoss.zkmax.ui.comet.CometAsyncServlet$AsyncInfo.complete(CometAsyncServlet.java:150) at org.zkoss.zkex.ui.comet.CometServerPush.cleanAsyncInfo(CometServerPush.java:340) at org.zkoss.zkex.ui.comet.CometServerPush.processRequest(CometServerPush.java:271) at org.zkoss.zkmax.ui.comet.CometServerPush.processRequest(CometServerPush.java:106) at org.zkoss.zkmax.ui.comet.CometAsyncServlet.doPost(CometAsyncServlet.java:116) at javax.servlet.http.HttpServlet.service(HttpServlet.java:641) at javax.servlet.http.HttpServlet.service(HttpServlet.java:722) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:395) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:250) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source)

feb 24, 2014 1:34:56 PM org.zkoss.bind.impl.BinderImpl$CommandEventListener onEvent:1329 SEVERE: null java.lang.NullPointerException at org.zkoss.zkmax.ui.comet.CometAsyncServlet$AsyncInfo.complete(CometAsyncServlet.java:150) at org.zkoss.zkex.ui.comet.CometServerPush.cleanAsyncInfo(CometServerPush.java:340) at org.zkoss.zkex.ui.comet.CometServerPush.schedule(CometServerPush.java:229) at org.zkoss.zk.ui.impl.DesktopImpl.scheduleServerPush(DesktopImpl.java:1469) at org.zkoss.zk.ui.Executions.schedule(Executions.java:873) at org.zkoss.zk.ui.event.impl.ServerPushEventQueue$DesktopInfo.publish(ServerPushEventQueue.java:157) at org.zkoss.zk.ui.event.impl.ServerPushEventQueue$DesktopInfo.access$000(ServerPushEventQueue.java:137) at org.zkoss.zk.ui.event.impl.ServerPushEventQueue.publish(ServerPushEventQueue.java:53) at PosterVM.postEvent(PosterVM.java:11) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.zkoss.bind.impl.ParamCall.call(ParamCall.java:111) at org.zkoss.bind.impl.BinderImpl.doExecute(BinderImpl.java:1745) at org.zkoss.bind.impl.BinderImpl.doCommand(BinderImpl.java:1506) at org.zkoss.bind.impl.BinderImpl.access$1500(BinderImpl.java:107) at org.zkoss.bind.impl.BinderImpl$CommandEventListener.onEvent0(BinderImpl.java:1375) at org.zkoss.bind.impl.BinderImpl$CommandEventListener.onEvent(BinderImpl.java:1327) at org.zkoss.zk.ui.AbstractComponent.onEvent(AbstractComponent.java:2743) at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:2714) at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:2655) at org.zkoss.zk.ui.impl.EventProcessor.process(EventProcessor.java:136) at org.zkoss.zk.ui.impl.UiEngineImpl.processEvent(UiEngineImpl.java:1721) at org.zkoss.zk.ui.impl.UiEngineImpl.process(UiEngineImpl.java:1506) at org.zkoss.zk.ui.impl.UiEngineImpl.execUpdate(UiEngineImpl.java:1216) at org.zkoss.zk.au.http.DHtmlUpdateServlet.process(DHtmlUpdateServlet.java:601) at org.zkoss.zk.au.http.DHtmlUpdateServlet.doGet(DHtmlUpdateServlet.java:483) at org.zkoss.zk.au.http.DHtmlUpdateServlet.doPost(DHtmlUpdateServlet.java:492) at javax.servlet.http.HttpServlet.service(HttpServlet.java:641) at javax.servlet.http.HttpServlet.service(HttpServlet.java:722) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:395) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:250) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:166) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source)

feb 24, 2014 1:34:56 PM org.zkoss.zk.ui.impl.UiEngineImpl handleError:1363 SEVERE: >>java.lang.NullPointerException

at org.zkoss.zkmax.ui.comet.CometAsyncServlet$AsyncInfo.complete(CometAsyncServlet.java:150) at org.zkoss.zkex.ui.comet.CometServerPush.cleanAsyncInfo(CometServerPush.java:340) at org.zkoss.zkex.ui.comet.CometServerPush.schedule(CometServerPush.java:229) at org.zkoss.zk.ui.impl.DesktopImpl.scheduleServerPush(DesktopImpl.java:1469) at org.zkoss.zk.ui.Executions.schedule(Executions.java:873) at org.zkoss.zk.ui.event.impl.ServerPushEventQueue$DesktopInfo.publish(ServerPushEventQueue.java:157) at org.zkoss.zk.ui.event.impl.ServerPushEventQueue$DesktopInfo.access$000(ServerPushEventQueue.java:137) at org.zkoss.zk.ui.event.impl.ServerPushEventQueue.publish(ServerPushEventQueue.java:53) at PosterVM.postEvent(PosterVM.java:11) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.zkoss.bind.impl.ParamCall.call(ParamCall.java:111) at org.zkoss.bind.impl.BinderImpl.doExecute(BinderImpl.java:1745) at org.zkoss.bind.impl.BinderImpl.doCommand(BinderImpl.java:1506) at org.zkoss.bind.impl.BinderImpl.access$1500(BinderImpl.java:107) at org.zkoss.bind.impl.BinderImpl$CommandEventListener.onEvent0(BinderImpl.java:1375) at org.zkoss.bind.impl.BinderImpl$CommandEventListener.onEvent(BinderImpl.java:1327) at org.zkoss.zk.ui.AbstractComponent.onEvent(AbstractComponent.java:2743) at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:2714) at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:2655) at org.zkoss.zk.ui.impl.EventProcessor.process(EventProcessor.java:136) at org.zkoss.zk.ui.impl.UiEngineImpl.processEvent(UiEngineImpl.java:1721) at org.zkoss.zk.ui.impl.UiEngineImpl.process(UiEngineImpl.java:1506) at org.zkoss.zk.ui.impl.UiEngineImpl.execUpdate(UiEngineImpl.java:1216) at org.zkoss.zk.au.http.DHtmlUpdateServlet.process(DHtmlUpdateServlet.java:601) at org.zkoss.zk.au.http.DHtmlUpdateServlet.doGet(DHtmlUpdateServlet.java:483) at org.zkoss.zk.au.http.DHtmlUpdateServlet.doPost(DHtmlUpdateServlet.java:492) at javax.servlet.http.HttpServlet.service(HttpServlet.java:641) at javax.servlet.http.HttpServlet.service(HttpServlet.java:722) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:395) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:250) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:166) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source)

For the most of time all work well.. But sometimes this strange thing happen!

P.S. I use ZK EE 6.5.5

Accepted Answer

answered 2014-02-24 13:37:35 +0800

chillworld

5322 ● 4 ● 9
https://github.com/chillw...

updated 2014-03-04 08:14:48 +0800

Can it be that you have a servlet named ServletPush declared in your web.xml? (this can be your problem)
Read this small talk : http://books.zkoss.org/wiki/SmallTalks/2009/August/ZK5:ChatwithEventQueue and you will see that there are no servlets configured.

Then a suggestion four your coding(it will be easier and cleaner to maintain) :

Actually you don't need the eventQueue in your java code cause you are working in MVVM, server push can also be done with global-commands.

Read this question: http://forum.zkoss.org/question/90813/postglobalcommand-in-application-scope/

If you have questions about this approuch let me know(small talk is coming for that topic).

edit :

I reviewed your program and there is nothing wrong with it. As I can see in the stacktrace you have another webprogram deployed on your tomcat. That program calls CometAsyncServlet at the path /ServerPush(the program you send calls ServerPush and path is / ).

Now go to your tomcat and undeploy that webprogram and you will have no error when restarting your tomcat.

Greetz chill.

Answer 2

0

answered 2014-03-02 09:51:04 +0800

Tristan2583
13 ● 3

I don't have any servlet named "ServletPush" declared in my web.xml. I'll look for the solution with global commands but I'd like to know why this problem happens.

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Comments

if its a test project, can you post in on dropbox/google drive/... in a zip file? I shall download it and review where the fault come from. Normally changing your code to the global- command will not solve your problem. Greetrz chill.

chillworld ( 2014-03-02 10:21:32 +0800 )edit

I've zipped and uploaded the entire ( stupid ) eclipse project on google drive. That's the link: https://drive.google.com/folderview?id=0B63v7RiKCWbvT3Y4bjRPY3N4T0E&usp=sharing

Thanks so much for your help!

Tristan2583 ( 2014-03-03 16:45:09 +0800 )edit

CometServerPush problem

2 Answers

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