The PreDestroy annotation is used on methods as a callback notification to signal that the instance is in the process of being removed by the container.

  The PreDestroy annotation is used on methods as a callback notification to
signal that the instance is in the process of being removed by the
container. The method annotated with PreDestroy is typically used to
release resources that it has been holding. This annotation MUST be
supported by all container managed objects that support PostConstruct
except the application client container in Java EE 5. The method on which
the PreDestroy annotation is applied MUST fulfill all of the following
criteria -
- The method MUST NOT have any parameters except in the case of EJB
interceptors in which case it takes an InvocationContext object as defined
by the EJB specification.
- The return type of the method MUST be void.
- The method MUST NOT throw a checked exception.
- The method on which PreDestroy is applied MAY be public, protected,
package private or private.
- The method MUST NOT be static.
- The method MAY be final.
- If the method throws an unchecked exception it is ignored except in the
case of EJBs where the EJB can handle exceptions.