Hi,
I've been getting a lot of grief trying to make some of my pages stateless
in Wicket 1.4.5 with Tomcat 6.0.
Here's one thing that doesn't work. I'm trying to make a session-resistant
(but *not* bookmarkable) link on the homepage that should work no matter if
the page exists. If the page doesn't exist, I want it to be created and then
the link event handler invoked. As far as I understand, StatelessLink should
work for this purpose. However, I can't get it to work. From time to time,
clicking it produces the following error in the console:
SEVERE: unable to find listener interface ILinkListener
org.apache.wicket.WicketRuntimeException: unable to find listener interface
ILinkListener
at
org.apache.wicket.request.target.component.BookmarkableListenerInterfaceRequestTarget.processEvents(BookmarkableListenerInterfaceRequestTarget.java:159)
at
org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:92)
at
org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1250)
at org.apache.wicket.RequestCycle.step(RequestCycle.java:1329)
at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1428)
at org.apache.wicket.RequestCycle.request(RequestCycle.java:545)
at
org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:479)
at
org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:312)
at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at
org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:390)
at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
at
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at
org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
at java.lang.Thread.run(Thread.java:619)
Sometimes I also get the following (seemingly related) error:
org.apache.wicket.protocol.http.request.InvalidUrlException:
org.apache.wicket.WicketRuntimeException: Unable to instantiate Page class:
com.my.HomePage. See below for details.
at
org.apache.wicket.protocol.http.WebRequestCycleProcessor.resolve(WebRequestCycleProcessor.java:262)
at org.apache.wicket.RequestCycle.step(RequestCycle.java:1310)
at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1428)
at org.apache.wicket.RequestCycle.request(RequestCycle.java:545)
at
org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:479)
at
org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:312)
at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at
org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:390)
at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
at
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at
org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
at java.lang.Thread.run(Thread.java:619)
Caused by: org.apache.wicket.WicketRuntimeException: Unable to instantiate
Page class: com.my.HomePage. See below for details.
at
org.apache.wicket.request.AbstractRequestCycleProcessor.resolveBookmarkablePage(AbstractRequestCycleProcessor.java:286)
at
org.apache.wicket.protocol.http.WebRequestCycleProcessor.resolve(WebRequestCycleProcessor.java:78)
... 20 more
Caused by: org.apache.wicket.WicketRuntimeException: Attempt to access
unknown request listener interface ILinkListener
at
org.apache.wicket.request.AbstractRequestCycleProcessor.resolveListenerInterfaceTarget(AbstractRequestCycleProcessor.java:407)
at
org.apache.wicket.request.AbstractRequestCycleProcessor.resolveBookmarkablePage(AbstractRequestCycleProcessor.java:266)
... 21 more
A reliable way to reproduce it is:
1) open the home page in the browser
2) restart the web application in Tomcat
3) click the link
Every time I perform the above steps, I either get the first exception, or
the second.
It doesn't necessarily happen immediately when the session expires (but
AFAICT it always happens some time after that). Looks like it happens when a
classloader cache in the servlet container gets garbage-collected.
I find the first stack trace especially interesting. I have traced the
execution flow in debugger, and I'm confident that the first exception
always happens after some Links get instantiated, and because Link
implements ILinkListener, at that point the RequestListenerInterface
instance for ILinkListener exists. However,
RequestListenerInterface.register() method doesn't get called during the
"resolve" step, so I must conclude that the servlet container uses the
preexisting class at that point. But when the execution flow
reachesAbstractRequestCycleProcessor.java:92 during the "process"
step, the RequestListenerInterface instance for ILinkListener can no longer
be found.
Such inconsistencies happen when one class (in this case,
AbstractRequestCycleProcessor)
is created by a different classloader than another class (ILinkListener).
What remains unclear is why I can't see other reports of the same problem on
the list. Am I doing something wrong?
Thanks,
-Kirill
