Using a RequestSelector

Another way to access request parameters in the sitemap is using a RequestSelector.

Some advantages over a RequestParamAction are that

you can use a default stylesheet when the parameter is not present,
you can change the stylesheet filenames without changing the request parameter values.

Defining the Selector

First, you have to define the selector in the components section of the sitemap:

<map:components>
  ...
  <map:selectors default="request">
    <map:selector name="request"
      src="org.apache.cocoon.selection.RequestSelector"/>
  </map:selectors>
  ...
</map:components>

Using the selector

A possible use of the selector is selecting the XSLT stylesheet based on a certain request parameter. When you pass the parameter "style=fancy" in the URI, the stylesheet fancy-style.xsl is used to transform the XML source. If you use another value for this parameter, or omit it, the stylesheet default-style.xsl is used.

<map:match pattern="*">
  <map:generate src="http://host.com/{1}.xml"/>
  <map:select type="request">
    <map:parameter name="parameter-name" value="style"/>
    <map:when test="fancy">
      <map:transform src="fancy-style.xsl"/>
    </map:when>
    <map:otherwise>
      <map:transform src="default-style.xsl"/>
    </map:otherwise>
  </map:select>
  <map:serialize/>
</map:match>