The Atlassian Plugin Framework 2 replaces the original Atlassian Plugins framework, described in the Developer Network. The new framework is based on OSGi, a dynamic module system for Java.
Almost every Atlassian product has a version of the Atlassian Plugin Framework, however, they may not be the same version. Eventually, each Atlassian application (Confluence, FishEye, Crucible, Crowd, etc) will be upgraded to version 2.0, but many are running version 1 today. If you are developing a plugin, you need to know what your version is capable of, and how it will interact with other versions.
 | The Atlassian Plugin Framework 2 is available in some, but not all, Atlassian applications
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Atlassian Plugin Framework 2.0 is available in: