3 ways in creating custom error pages

1. web.xml

The standard webapp configuration file located in <webapp>/WEB-INF/web.xml can be used to map errors to specific URLs with the <error-page> element. This element creates a mapping between the error-code or exception typ to the location of a resource in the web application.

error-code - integer value
exception-type - fully qualified class name of a Java Exception type
location - location of the resource in webapp relative to the root of the web application. Value should start with "/".

Error code example:

<error-page>
  <error-code>404</error-code>
  <location>/jspsnoop/ERROR/404</location>
</error-page>

Exception example:

<error-page>
  <exception-type>java.io.IOException</exception-type>
  <location>/jspsnoop/IOException</location>
</error-page>

2. context file configuration.

Context files are nomrall located in <jetty.home>/contexts/?.xml (see ContextDeployer for more detail). Context files
can be used to configure the default error handler provided for a context with more flexibility than is available with web.xml,
specifically with the support of error code ranges:

<?xml version="1.0"  encoding="ISO-8859-1"?>
<!DOCTYPE Configure PUBLIC "-//Mort Bay Consulting//DTD Configure//EN" "http://jetty.mortbay.org/configure.dtd">

<Configure class="org.mortbay.jetty.webapp.WebAppContext">
  <Set name="contextPath">/test</Set>
  <Set name="war">
    <SystemProperty name="jetty.home" default="."/>/webapps/test
  </Set>

  <!-- by Code -->
  <Get name="errorHandler">
    <Call name="addErrorPage">
      <Arg type="int">404</Arg>
      <Arg type="String">/jspsnoop/ERROR/404</Arg>
    </Call>
  </Get>

  <!-- by Exception -->
  <Get name="errorHandler">
    <Call name="addErrorPage">
      <Arg type="java.lang.Class">java.io.IOException</Arg>
      <Arg type="String">/jspsnoop/IOException</Arg>
    </Call>
  </Get>

  <!-- by Code Range -->
  <Get name="errorHandler">
    <Call name="addErrorPage">
      <Arg type="int">500</Arg>
      <Arg type="int">599</Arg>
      <Arg type="String">/dump/errorCodeRangeMapping</Arg>
    </Call>
  </Get>
</Configure>

3. Custom error handle class.

A context may be configured with a custom error handler class that extends ErrorHandler (for webapp contexts
it must extend ErrorPageErrorHandler).

The following methods may be implemented to control the appearance of the error pages:

public void handle(String target, HttpServletRequest request, HttpServletResponse response, int dispatch) throws IOException
void handleErrorPage(HttpServletRequest request, Writer writer, int code, String message) throws IOException
void writeErrorPage(HttpServletRequest request, Writer writer, int code, String message, boolean showStacks) throws IOException
void writeErrorPageHead(HttpServletRequest request, Writer writer, int code, String message) throws IOException
void writeErrorPageBody(HttpServletRequest request, Writer writer, int code, String message, boolean showStacks) throws IOException
void writeErrorPageMessage(HttpServletRequest request, Writer writer, int code, String message,String uri) throws IOException
void writeErrorPageStacks(HttpServletRequest request, Writer writer) throws IOException

The custom error handler may be set on the context via the API or via a context configuration file. For example a custom error handling class can be added to the javadoc context with:

<?xml version="1.0"  encoding="ISO-8859-1"?>
<!DOCTYPE Configure PUBLIC "-//Mort Bay Consulting//DTD Configure//EN" "http://jetty.mortbay.org/configure.dtd">

<Configure class="org.mortbay.jetty.handler.ContextHandler">
  <Call class="org.mortbay.log.Log" name="debug"><Arg>Configure javadoc.xml</Arg></Call>
  <Set name="contextPath">/javadoc</Set>
  <Set name="resourceBase"><SystemProperty name="jetty.home" default="."/>/javadoc/</Set>

  <!-- Instantiate your own error handler -->
  <Set name="errorHandler">
    <New class="com.acme.handler.MyErrorHandler"/>
  </Set>

</Configure>