JavaServer Pages, 3rd Edition

Aborting the Page Processing

For some custom actions, the processing of the page must stop after the custom action has been processed. An example is a custom action that redirects or forwards to another page, such as the JSTL <c:redirect> action.

A simple tag handler can throw a javax.servlet.jsp.tagext.SkipPageException to signal to the container that the rest of the page must not be evaluated. The container respects this no matter how deeply the custom action is nested within bodies of other actions. To show how it’s done, here’s a simple tag handler with the sole purpose of aborting the page processing:

package com.ora.jsp.tags.xmp;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;

public class AbortPageTag extends SimpleTagSupport {
    public void doTag(  ) throws JspException {
        throw new SkipPageException(  );
    }
}

You could use this feature to, for instance, develop a smart forwarding action that decides which page to forward to based on runtime conditions, such as the time of the day, the current user, or the type of browser accessing the page. After the forwarding call, throwing the SkipPageException terminates the processing of the rest of the page that contains the forwarding action.