Another post about Spring Portlet MVC.  Currently in Spring 3.1.2(and 3.1.1 as far as I can tell) there is a problem with portlet annotation handler mapping apparently due to a flaw in predicate comparison; its documented more in depth in their jira at SPR-9303.  The issue has been reported to have been fixed for Spring 3.1.3, but until that comes out I had to find a work around.

The hard part about diagnosing this bug is that it may or may not affect your portlet depending on how many annotation handlers you have, how they are structured, and in what order they are picked up by Spring.  Many of the portlets we have created haven’t had any problems(or none that we have experienced so far), but one portlet in particular was mapping every single render request to its default mapping.  Someone on stackoverflow has investigated the ordering further and shows exactly why the ordering matters.  Long story short, if the default handler mapping isn’t ordered last then any handler mappings behind it will never get used.

A workaround is simple enough, albeit a little ugly.  Remove the default annotation handler mapping method into its own class and package and have Spring component-scan to register it separately.  Like so:

<context:component-scan base-package=”com.kwilkins.portlets.foo”>
<context:exclude-filter type=”regex” expression=”com.kwilkins.portal.foo.controller.springbug..*”/>
</context:component-scan>
<!– This package temporarily exists due to spring bug; SPR-9303 –>
<context:component-scan base-package=”com.kwilkins.portlets.foo.controller.springbug”/>

Doing this should scan and register the default mapping after everything else already has been.