Atlassian products each define a set of plugin points, where plugins can add functionality. Each module type provides functionality to a different plugin point. For example, the event system will send events to all the modules of type 'Event Listener' in all the plugins loaded by Fisheye/Crucible.
Module Types Supported in Fisheye/Crucible
Downloadable Plugin Resources -- If your plugin requires Fisheye/Crucible to include additional static files such as images, you will need to use downloadable plugin resources to make them available.
Event Listener Module Type -- An event listener plugin module is an object which is notified when certain internal Crucible or Fisheye events occur.
Gadget Module Type -- A Gadget module allows Fisheye/Crucible to serve your gadget.xml file. See Gadget Development for more details on developing gadgets.
Gutter Renderer Module Type -- The Gutter Renderer plugin point allows you to display custom content in the margin of your source code view.
REST Module Type -- You can use the REST module type to expose services and data entities as REST APIs
SCM Module Type -- An SCM plugin module gives Crucible the ability to work with a custom version control system that is not supported out of the box.
Servlet Module Type -- Servlet plugin modules enable you to deploy Java servlets as a part of your plugins.
Spring Component Module Type -- Component plugin modules enable you to share Java components between other modules in your plugin and optionally with other plugins in the application.
Web Item Module Type -- Web UI plugin modules allow you to add links, tabs and sections of links to the Fisheye user interface. By adding a link to a servlet plugin, you can add your own pages to the UI.
Web Panel Module Type -- Web Panel plugin modules allow you to add a string of HTML to particular points in the Fisheye user interface. By including a link to a servlet plugin, you can add your own pages to the UI.
Workflow Condition Module Type -- The Workflow Condition plugin point allows you to prevent review transition from happening depending on the conditions you've implemented.