Adding Cache-control settings to HTTP-header using Jetty web server

Symptoms

The Expires-directive in the HTTP-header is automatically added to all VoiceXML pages generated by VoiceObjects Server. This cannot be modified. The directive remains:

Expires: Thu, 01 Jan 1970 00:00:00 GMT

Some speech platforms require additional information in the HTTP-Header in order to ensure correct communication with VoiceObjects Server (e.g. prevent caching of VoiceXML-pages).

This article explains how to add those HTTP directives if using Jetty as web server.

Resolution

Adding HTTP-Header elements can be achieved by adding following XML-elements to the respective Jetty configuration file for VoiceObjects Server (?/WEB-INF/etc/Jetty5/VOServer.xml).

For example if you want to add the HTTP-Header element

Cache-Control: no-cache

for all VXML pages sent by VoiceObjects Server follow these steps:

1. Create a backup copy of the VOServer.xml
2. Open the file and search for:

   <Call name="addWebApplication">
   	<Arg>/VoiceObjects</Arg>
   	<Arg><!-- VoiceObjects Installation directory --></Arg>
   </Call>
   

3. Add the following section

   <Call name="addWebApplication">
   	<Arg>/VoiceObjects</Arg>
   	<Arg><!-- VoiceObjects Installation directory --></Arg>
   	<Call name="addHandler">
   		<Arg>
   			<New class="org.mortbay.http.handler.SetResponseHeadersHandler">
   				<Call name="setHeaderValue">
   					<Arg type="String">Cache-Control</Arg>
   					<Arg>no-cache</Arg>
   				</Call>
   			</New>
   		</Arg>
   	</Call>
   </Call>

4. Save the file and restart the server.

For convenience you can also easily add the same directive with multiple values using the <Array>-element: Lets take e.g.

   Cache-Control: no-cache Cache-Control: public

will be produced by the following block:

<Call name="addWebApplication">
	<Arg>/VoiceObjects</Arg>
	<Arg><!-- VoiceObjects Installation directory --></Arg>
	<Arg>
		<New class="org.mortbay.http.handler.SetResponseHeadersHandler">
			<Call name="setHeaderValues">
				<Arg type="String">Cache-Control</Arg>
				<Arg>
					<Array type="java.lang.String">
						<Item>no-cache</Item>
						<Item>public</Item>
					</Array>
				</Arg>
			</Call>
		</New>
	</Arg>
</Call>

Further information

For further information refer to

• http://www.ietf.org/rfc/rfc2616.txt
• http://jetty.codehaus.org/jetty/