[Struts Wiki] Update of "ErrorCannotRetrieveMappingForAction" by MichaelJouravlev

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The following page has been changed by MichaelJouravlev:
http://wiki.apache.org/struts/ErrorCannotRetrieveMappingForAction

New page:
If the Application is split in to different modules and if the flow goes to the JSP, with an <html:form> tag, an exception
such as '''Cannot retrieve mapping for Action /action''' can be thrown, if the <html:form> tag's action path is referencing
an action in a submodule. The reason being <html:form> tag looks for the '''ModuleConfig''' first in the request, 
if it doesn't find it there, it retrieves from the '''ServletContext'''. Since, the tag cannot know the module 
the action belongs to it retrieves the default '''ModuleConfig''' and so the exception.

[:StrutsCatalogLinkOnlyToActions:Link only to Actions] pattern gets rid of this exception, since the corresponding '''ModuleConfig''' is placed in the request by ActionServlet (or RequestProcessor). One more reason for linking only to Actions.