Annotation is a new feature in Java 5.0 that when declared can contain metadata at compile and run time. It is well suited for aop declaration since there will be no need for external metadata xml descriptor. In order to support Java 1.4 as well, JBossAop has also used a xdoclet type annotation syntax, and as a result will need an annotation pre-compiler.

Note that PojoCache starts to support the use of annotation since release 1.2.3 with Java 1.4, and release 1.3 with Java 5.0.