JavaServer Pages, Second Edition

Using a Common JSP Error Page

Before we end the exploration of the combination of JSP and servlets, I’d like to give you one more useful tip, namely how to use a JSP error page that displays a user-friendly error page for all runtime errors, no matter if they originate in a JSP page, a servlet, or a filter.

In Chapter 9, I showed you how to use the page directive’s errorPage attribute to specify a JSP page that is invoked in case an exception is thrown while processing the page. I also mentioned that an alternative is to declare an error page in the deployment descriptor (the WEB-INF/web.xml file). It’s then used for exceptions thrown by a servlet, a filter, or a JSP page that doesn’t declare an error page:

<error-page>
  <exception-type>java.lang.Throwable</exception-type>
  <location>/errorpage.jsp</location>
</error-page>

To recap, the <exception-type> element contains the fully qualified name of the type of exception you want to handle with the servlet, JSP page, or static page specified by the <location> element. The <location> value must be a context-relative path (starting with a slash). You can use multiple <error-page> elements to use different pages for different exceptions, and the container picks the one with the <exception-type> element that most closely matches the type of the exception thrown.

There’s one problem, though: if you use a JSP page to handle the exception, you can’t log or display the exception message, because a JSP page invoked this way doesn’t have access ...