Christoph Läubrich created WICKET-5466:
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Summary: ListenerInterfaceRequestHandler#respond throws
ComponentNotFoundException as a side-effect
Key: WICKET-5466
URL: https://issues.apache.org/jira/browse/WICKET-5466
Project: Wicket
Issue Type: Bug
Components: wicket
Affects Versions: 6.12.0
Reporter: Christoph Läubrich
The following exception occurs instead of a generic WicketRuntimeException:
16:27:56.181 WARN (RequestCycle.java:343) Handling the following exception
[qtp9826071-207]
org.apache.wicket.core.request.handler.ComponentNotFoundException: Could not
find component 'xyz' on page 'class MyPage’
at
org.apache.wicket.core.request.handler.PageAndComponentProvider.getComponent(PageAndComponentProvider.java:182)
~[org.apache.wicket.core_6.12.0.jar:6.12.0]
at
org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.getComponent(ListenerInterfaceRequestHandler.java:90)
~[org.apache.wicket.core_6.12.0.jar:6.12.0]
at
org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.respond(ListenerInterfaceRequestHandler.java:231)
~[org.apache.wicket.core_6.12.0.jar:6.12.0]
at
org.apache.wicket.request.cycle.RequestCycle$HandlerExecutor.respond(RequestCycle.java:861)
~[org.apache.wicket.core_6.12.0.jar:6.12.0]
at
org.apache.wicket.request.RequestHandlerStack.execute(RequestHandlerStack.java:64)
~[org.apache.wicket.request_6.12.0.jar:6.12.0]
at
org.apache.wicket.request.cycle.RequestCycle.execute(RequestCycle.java:261)
[org.apache.wicket.core_6.12.0.jar:6.12.0]
at
org.apache.wicket.request.cycle.RequestCycle.processRequest(RequestCycle.java:218)
[org.apache.wicket.core_6.12.0.jar:6.12.0]
at
org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:289)
[org.apache.wicket.core_6.12.0.jar:6.12.0]
at
org.apache.wicket.protocol.http.WicketFilter.processRequestCycle(WicketFilter.java:259)
[org.apache.wicket.core_6.12.0.jar:6.12.0]
in fact, this is a side effect, if you look at the code:
@Override
public void respond(final IRequestCycle requestCycle)
{
final IRequestablePage page = getPage();
final boolean freshPage =
pageComponentProvider.isPageInstanceFresh();
final boolean isAjax =
((WebRequest)requestCycle.getRequest()).isAjax();
IRequestableComponent component = null;
try
{
component = getComponent();
}
catch (ComponentNotFoundException e)
{
// either the page is stateless and the component we are
looking for is not added in the
// constructor
// or the page is stateful+stale and a new instances was
created by pageprovider
// we denote this by setting component to null
component = null;
}
if ((component == null && freshPage) ||
(component != null && getComponent().getPage() == page))
{
[....]
}
else
{
throw new WicketRuntimeException("Component " +
getComponent() +
" has been removed from page.");
}
}
You see that getComponent() is called twice.
1) Once guarded by a catch and once unguarded. So if the component can't be
found AND freshPage is false, as a sideeffect instead of the
WicketRuntimeException with the removed message a componentnotfound exception
is raised as a side effect.
I see two possible solutions for this
a) either it is intentional that a ComponentNotFoundException is thrown, then
it should be thrown from the catch block like
catch (ComponentNotFoundException e)
{
if (!freshPage) {
throw e;
}
}
b) if it is unintentionall in the else case ther should be a simple check like
this
if (component == null) {
throw new WicketRuntimeException("Component for path "
+ getPath() +
" and page "+page.getClass().getName()+" has been
removed from page.");
} else {
throw new WicketRuntimeException("Component " +
component +
" has been removed from page.");
}
Beside this: it would be a good idea to mention at least the page class in
either case.
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