I'm new to JMS and i wandered if i can to use Messages to inform the rest of the program about changes in the Modell. Currently, my SessionBean methods contains lot of code to inform other SessionBeans, that something was changed. The methods grown to hunderts of lines and code is duplicated all over the application. Are are the MessageBeans good solution?

Offcourse you can implement Observer Pattern with JMS, by creating a Publish-Subscribe channel you can get along with the pattern. For any more resources, feel free to ask. cheers, http://javaicillusion.blogspot.com/