Calling java from xsl - with xml as parameter

Hi.

I hava a xml and a xsl which are being parsed.

In the xsl i want to call a java method with a parameter, which 
contains the source xml. The parameter can be of any type.
The java program returns a String.

The problem is to send the xml as parameter to the java method.

I have tried following:
Copy / Store the xml document in the variable xmlString.
<xsl:variable name="xmlString">
	<xsl:copy-of select="/*[local-name()='Invoice']" />
</xsl:variable>

Send the xmlString to the java method rtrtransform, but the problem 
is, that it only sends the values to the java method. When i want to 
send "<abc><d>hi</d><e>there<e></abd>", i only get "hithere". Tags are 
not send.
<xsl:variable name="myresult">
	<xsl:value-of select="transf:rtrtransform(string($xmlString))"/>
</xsl:variable>


I thought i could solve the problem by using xsl:copy-of select... , 
but that seems to be illegal:
	<xsl:value-of select="transf:rtrtransform(string(<xsl:copy-of select="
abc" />"/>
or
	<xsl:value-of select="transf:rtrtransform(string(&lt;xsl:copy-of 
select=&#034;abc&#034; /&gt;"/>


Any solutions to this?

Best regards
Richard Trans