Singleton class to be shared among multiple portlets

Question

I have a couple of Singleton classes in a Liferay application that hold several configuration parameters and a ServiceLocator with instances to WebServices I need to consume.

I have put these classes in a jar that is declared as a dependency on all my portlets.

The thing is, I have put some logging lines for initialization in theses singleton classes, and when I deploy my portlets I can see these lines multiple times, once for every portlet, since each portlet has its own class context.

For the AppConfig class it might not be such a big deal but my ServiceLocator does actually hold a bunch of references that take a good bit of memory.

Is there any way that I can put these Singleton references in some kind of Shared context in my Liferay Portal?

Answer 1

The problem is that every Portlet runs in its own WAR file and aech war file has its own classloader.

Usually when I had to achieve a requirement like this, I had to put the Singleton classen in a JAR file and this JAR file in the common class loader library instead of packing it into each WAR. (In Tomcat: <tomcatHome>/common/lib or something like that)

Then you'll also have to put all dependent libraries into that common lib dir, too. Don't know how to do that in Liferay, though. For tomcat see this thread: stackoverflow.com/questions/267953/ and this documentation: http://tomcat.apache.org/tomcat-7.0-doc/class-loader-howto.html. Depends on the Servlet container.