Java Enterprise Best Practices

Use Common Error Pages for the Whole Application

The JSP page directive’s errorPage attribute can be used to specify a page to be invoked when an error occurs while processing the page. The page can be a static HTML file, a servlet, or a JSP page. A JSP page used as an error page (designated as such by the page directive’s isErrorPage attribute) has access to a Throwable instance that represents the error through the implicit exception scripting variable, or through the EL expression ${pageContext.exception}.

While this mechanism might be suitable for a small application using only JSP pages, it’s not appropriate for an enterprise application using a combination of servlets, filters, and JSP pages. Using a shared error handler for all these component types lets you better control error handling and fine-tune it in one place when needed. To use a global error handler, do not use the errorPage attribute in the JSP pages. Instead, declare an error handler in the web application deployment descriptor (the web.xml file):

<web-app>
   . . . 
  <servlet>
    <servlet-name>errorHandler</servlet-name>
    <servlet-class>
      com.ora.jsp.servlets.ErrorHandlerServlet
    </servlet-class>
    <init-param>
      <param-name>errorPage</param-name>
      <param-value>/shared/error.html</param-value>
    </init-param>
  </servlet>
   . . . 
  <error-page>
    <exception-type>java.lang.Throwable</exception-type>
    <location>/errorHandler</location>
  </error-page>
   . . . 
</web-app>

Here, I define a servlet as the error handler for all types of exceptions; ...