Configuring Methods Using Annotations in Web Applications

Use

You can define the moment when a method is called by using the corresponding annotations.

There are two annotations for configuring method invocation:

@PostConstruct

This annotation specifies that the method will be called before all lifecycle methods are called.
@PreDestroy

This annotation specifies that the method will be called before the servlet object is destroyed.

Procedure

Using the @PostConstruct Annotation

Use this annotation at method level without any attributes.

Sample Code

                  public class PostConstructAnnot_servlet extends HttpServlet {

//…

        @PostConstruct
        public void postConstruct() {
                //Invocation of init methods, preparative operations
                System.out.println("PostConstructAnnot_servlet: "
                                + " postConstruct method invoked! ");
        }

//…

}

Using the @PreDestroy Annotation

Use this annotation at method level without any attributes.

Sample Code

                  public class PreDestroyAnnot_servlet extends HttpServlet {

//…

@PreDestroy
    public void preDestroy(){
         //Clean up any open resources
             System.out.println("PreDestroyAnnot_servlet: " +
                                " preDestoy method invoked! "); 
    }

//…