Xalan-J: Setting Objects as Parameters in XSL

I am trying to use the Transformer.setParameter method with a
java.util.HashMap, but the transform tries to use a String type. If I
specify a default in XSL like:

I then just get an empty HashMap. Anyone know how to make this work?
Here's the Java code:

 HashMap propertyMap = new HashMap();
 propertyMap.put("membership", "0000000");
/* more stuff */
 transformer.setParameter("propertyMap", propertyMap);
 transformer.transform(source, result);

<xsl:stylesheet	
  version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:java="http://xml.apache.org/xslt/java"
  exclude-result-prefixes="java">

  <xsl:param name="parameterMap" select="java:java.util.HashMap.new" />
  <xsl:output method="html" />
  <!-- More stuff -->
   <xsl:variable name="foo" value="membership" />
   <xsl:value-of select="java:get($parameterMap, $foo)"/>

--
Seth Milder
Department of Physics and Astronomy
MS 3f3
George Mason University
Fairfax, VA
http://www.mrseth.org
--
Questions are never indiscreet, answers sometimes are. -- Oscar Wilde