Check Page Exception : PageContext « JSP « Java Tutorial


<%@ page errorPage="processError.jsp" %>    
<%-- Declare the page to send errors to --%>

<%-- This scriptlet checks a hidden field to see whether or not to throw an exception --%>
  String hiddenField = request.getParameter("hiddenValue");
  if ( hiddenField !=null && !hiddenField.equals(""))
    throw new java.lang.NullPointerException();

  <HEAD><TITLE>Generate Error</TITLE></HEAD>
    This page generates an error when you click the button.<P>
    <FORM METHOD="POST" ACTION="index.jsp">
      <INPUT TYPE="HIDDEN" NAME="hiddenValue" VALUE="Bang!">
      <INPUT TYPE="SUBMIT" VALUE="Generate exception!">


<%@ page isErrorPage="true" %>

  <HEAD><TITLE>Process Error</TITLE></HEAD>
    <% if ( exception != null ) {
         out.write("\nAn error occurred. This page is to tell you what you did wrong.\n");
       else {
         out.write("\nYou have reached this page, but no error information is available.\n");
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23.33.1.Save Value to PageContext
23.33.2.Set PageContext Attribute in JSP Page
23.33.3.Do Calculation on Value Saved in PageContext
23.33.4.Dispatch Page Based on Form Input
23.33.5.Compare Attribute in PageContext
23.33.6.Check Page Exception