How to specify a sortBy through a javax.xml.transform.Transformer.transform() call?

I'm using javax.xml.transform.Transformer.transform() to convert one xml to another through an xsl stylesheet. I would like to programatically set the sorting of the first level of children, but am unsure how to go about it. I've checked out the docs, but I don't understand which type of property/parameter to use and how to specify in sort:

<xsl:sort select="*need to get property or parameter to here*"/>

I am open to other ideas, but would rather not parse the xml result into a w3c document.

Edit: To clarify I am looking to set the sort key and direction for the elements in a xsl:for-each tag via the Transf开发者_如何学JAVAormer API.

This stylesheet:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:param name="pSortingBy" select="/root/@sorting"/>
    <xsl:template match="node()|@*">
        <xsl:copy>
            <xsl:apply-templates select="node()|@*"/>
        </xsl:copy>
    </xsl:template>
    <xsl:template match="/root">
        <xsl:copy>
            <xsl:apply-templates select="node()|@*">
                <xsl:sort select="*[name()=$pSortingBy]"/>
            </xsl:apply-templates>
        </xsl:copy>
    </xsl:template>
</xsl:stylesheet>

With this input:

<root sorting="prop4">
    <elem1>
        <prop1>A</prop1>
        <prop2>B</prop2>
        <prop3>C</prop3>
        <prop4>D</prop4>
        <prop5>A</prop5>
    </elem1>
    <elem2>
        <prop1>B</prop1>
        <prop2>C</prop2>
        <prop3>D</prop3>
        <prop4>A</prop4>
        <prop5>B</prop5>
    </elem2>
    <elem3>
        <prop1>C</prop1>
        <prop2>D</prop2>
        <prop3>A</prop3>
        <prop4>B</prop4>
        <prop5>C</prop5>
    </elem3>
</root>

Output:

<root sorting="prop4">
    <elem2>
        <prop1>B</prop1>
        <prop2>C</prop2>
        <prop3>D</prop3>
        <prop4>A</prop4>
        <prop5>B</prop5>
    </elem2>
    <elem3>
        <prop1>C</prop1>
        <prop2>D</prop2>
        <prop3>A</prop3>
        <prop4>B</prop4>
        <prop5>C</prop5>
    </elem3>
    <elem1>
        <prop1>A</prop1>
        <prop2>B</prop2>
        <prop3>C</prop3>
        <prop4>D</prop4>
        <prop5>A</prop5>
    </elem1>
</root>

Note: You could define pSortingBy param to be any element name following specifications from your XSLT processor.

Edit: I'm not a java expert, but I think you could do:

javax.xml.transform.TransformerFactory transFact =
                       javax.xml.transform.TransformerFactory.newInstance( );
javax.xml.transform.Transformer trans = transFact.newTransformer(xsltSource);
trans.setParameter("pSortingBy", "prop5");

It needs to go in a for-each or apply-templates, and you specify the expression to sort on.

From http://www.w3schools.com/xsl/el_sort.asp:

 <xsl:for-each select="catalog/cd">
      <xsl:sort select="artist"/>
      <tr>
        <td><xsl:value-of select="title"/></td>
        <td><xsl:value-of select="artist"/></td>
      </tr>
    </xsl:for-each>