Why I can’t use portal-impl in my portlet?

When I started my adventure with liferay and I was young I had a big headache with a view: „Why liferay developers didn’t share portal-impl.jar for external portlets. This is so stupid”. When we don’t have access to this module our development is very difficult. I can’t extend my Action class and I must manually attend all incoming requests beacause portal-impl.jar provides most classes used by the portal’s portlets. Why I can’t use this one?

Today, when I spent a long time with liferay my answer is: NO, you should not use a portal-impl.jar in your portlet. Remember: NEVER put portal-impl into anywhere other than where it came from. This will cause untold problems beacause portal-impl is the central core of the portal and it is a main piece of cake. So you can’t put portal-impl in lib directory in your portlets or in other strange places. Why? Liferay uses all kinds of classloader tricks to get access to various classes. So adding portal-impl to library folder in your portlet will realy mess this up. There will be duplicated instances of classes which are load from different class loaders. Additionaly portal-impl.jar contains internal classes of liferay core implementation, so if you use it in this version remember that next one can change all method’s or just remove some classes.

In portal-service.jar liferay provides a set of methods, which you can use in your own implementation. It sits in the global classpath (on tomcat this is <tomcat>/lib/ext/*.jar). All the services and utilities are available from these.

Wait a second… this feature looks nice, but how can I develop my controller (for example struts)? You should use apache struts bridge to handle lifecycle of struts portlet (refer sample-struts-portlet in community svn plugin repository). Also Liferay provides some kinds of bridges (e.g. mvc, php, python and more) and it is the simplest and the best way to create your own action class or your own controller. In my opinion there are some very important reasons to do with this way:

• your code is totally independent
• portlets are more flexible
• there is a big chance that your code will be working with newer version of liferay
• you write code with framework you like

But Liferay’s StrutsPortlet bridge should not be used for any new development. If you really must use Struts 1.x it’s better to use Apache portlet bridge. You can also use Liferay’s MVCPortlet. Or, you can use one of the other frameworks supported by Liferay: Spring MVC, Struts 2, and JSF.

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