[WICKET-3918] NPE when requesting http://example.com/app/wicket/resource/org.apache.wicket.extensions.ajax.markup.html.modal.ModalWindow/res/

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.5-RC5.1
• Fix Version/s: 1.5-RC6
• Component/s: wicket
• Assignee: Martijn Dashorst
• Reporter: Martijn Dashorst
• Created: 19/Jul/11 13:09
• Updated: 19/Jul/11 14:03
• Resolved: 19/Jul/11 13:35

Description

When requesting the following URL, the default caching strategy throws a NullPointerException and this is logged. This request is performed by some spider agent of Microsoft (trying to kill Wicket!) with user agent 'Microsoft Office Protocol Discovery':

Url=http://example.com/app/wicket/resource/org.apache.wicket.extensions.ajax.markup.html.modal.ModalWindow/res/

java.lang.NullPointerException: caching strategy must not return an empty filename
at org.apache.wicket.request.mapper.BasicResourceReferenceMapper.mapRequest(BasicResourceReferenceMapper.java:102)
at org.apache.wicket.request.mapper.ParentPathReferenceRewriter.mapRequest(ParentPathReferenceRewriter.java:83)
at org.apache.wicket.request.mapper.CompoundRequestMapper.mapRequest(CompoundRequestMapper.java:129)
at org.apache.wicket.request.cycle.RequestCycle.resolveRequestHandler(RequestCycle.java:183)
at org.apache.wicket.request.cycle.RequestCycle.processRequest(RequestCycle.java:208)
at org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:253)
at org.apache.wicket.protocol.http.WicketFilter.processRequest(WicketFilter.java:160)
at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:216)

A couple of points:

• the exception should log which strategy caused the empty filename
• the exception might want to log the requested URL for the resource
• perhaps a NullPointerException is not the best exception to throw, but rather something that results in a 404 or a 403
• maybe not even throwing an exception is the best way to handle this case, instead rely on the container or another mapper to take the lead?