A JSR168-compliant implementation of inter-portlet communication

Note: there is now a new version of the messaging library available.

This portlet messaging library is intended for situations when:

  • You want to build an application out of several interacting portlets (e.g. a portlet which presents a list or index, and a number of portlets which display information about the selected item)
  • You've read this Tip on java.net and decided that the PortletSession is the way to go (if you wanted one of the other methods, have a look at Limitations in the Documentation)
  • You can't simply hardcode the messaging using APPLICATION_SCOPE session variables with known names, because:
    • Maybe you want many instances of the same portlet on the same page, or different pages, with each instance talking to different portlets
    • Maybe you want the user to be able to dynamically add new portlet instances, and configure the 'wiring' of messages between portlets.

This is my initial implementation of a slightly more complicated messaging system, for the Discovery Net project. Please let me know if you find it useful, or have any comments/advice/bugfixes that may make it better. The source is included and you're welcome to modify/use it however you like. It's free, no guarantees.
diagram showing basic messaging

Simple messaging model: message names in session must be hardcoded into the portlets

diagram showing messaging library

Advanced messaging model: message names in session do not need to be hardcoded. A Message Centre keeps track of all the mappings between local message names and global message names, allowing dynamic reconfiguration of message 'routes' by the administrator or the portal user.