Annotations enable you to write metadata for Enterprise JavaBeans (EJB) inside your source code. You can use them instead of extensible markup language (XML) deployment descriptor files. Annotations can also be used with descriptor files.
The WebSphere Application Server also provides default values for most of the EJB annotations it uses. In many cases, omitting an annotation implies that you want to use the default value.
For the most part, annotations are found in the javax.ejb and javax.persistence packages.