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XSL Result
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Added by casey, last edited by Ted Husted on Sep 10, 2006 (view change)

XSLTResult uses XSLT to transform action object to XML. Recent version has been specifically modified to deal with Xalan flaws. When using Xalan you may notice that even though you have very minimal stylesheet like this one

    <xsl:template match="/result">
      <result />
    </xsl:template>

then Xalan would still iterate through every property of your action and it's all descendants.

If you had double-linked objects then Xalan would work forever analysing infinite object tree. Even if your stylesheet was not constructed to process them all. It's becouse current Xalan eagerly and extensively converts everything to it's internal DTM model before further processing.

Thet's why there's a loop eliminator added that works by indexing every object-property combination during processing. If it notices that some object's property were already walked through, it doesn't get any deeper. Say, you have two objects x and y with the following properties set (pseudocode):

    x.y = y;
    and
    y.x = x;
    action.x=x;

Due to that modification the resulting XML document based on x would be:

    <result>
      <x>
        <y/>
      </x>
    </result>

Without it there would be an endless x/y/x/y/x/y/... elements.

The XSLTResult code tries also to deal with the fact that DTM model is built in a manner that childs are processed before siblings. The result is that if there is object x that is both set in action's x property, and very deeply under action's a property then it would only appear under a, not under x. That's not what we expect, and that's why XSLTResult allows objects to repeat in various places to some extent.

Sometimes the object mesh is still very dense and you may notice that even though you have relatively simple stylesheet execution takes a tremendous amount of time. To help you to deal with that obstacle of Xalan you may attach regexp filters to elements paths (xpath).

Note: In your .xsl file the root match must be named `result`.
This example will output the username by using `getUsername` on your action class:

    <xsl:template match="result">
      <html>
      <body>
      Hello <xsl:value-of select="username"/> how are you?
      </body>
      <html>
    <xsl:template/>

In the following example the XSLT result would only walk through action's properties without their childs. It would also skip every property that has "hugeCollection" in their name. Element's path is first compared to excludingPattern - if it matches it's no longer processed. Then it is compared to matchingPattern and processed only if there's a match.

    <result name="success" type="xslt">
      <param name="location">foo.xslt</param>
      <param name="matchingPattern">^/result/[^/*]$</param>
      <param name="excludingPattern">.*(hugeCollection).*</param>
    </result>

# Parameters

- location (default) - the location to go to after execution.

- parse - true by default. If set to false, the location param will not be parsed for Ognl expressions.

- matchingPattern - Pattern that matches only desired elements, by default it matches everything.

- excludingPattern - Pattern that eliminates unwanted elements, by default it matches none.

`struts.properties` related configuration:

- struts.xslt.nocache - Defaults to false. If set to true, disables stylesheet caching. Good for development, bad for production.

# Examples

    <result name="success" type="xslt">
      <param name="location">foo.xslt</param>
      <param name="matchingPattern">^/result/[^/*]$</param>
      <param name="excludingPattern">.*(hugeCollection).*</param>
    </result>