As we discussed in the previous sections, callback interfaces javax.ejb.SessionBean, and javax.ejb.EntityBean are not implemented by the session beans and entity beans respectively. The callback methods of these methods are not implemented by the session and entity beans. Any method may be made a callback method using the callback annotations such as PostActivate, PrePassivate, PreDestroy, and PostConstruct. The callback methods may be specified in a callback listener class instead of the bean class.