Dynamic xml filtering and transform (in Java)

Question

I have an XML file that looks like

<?xml version='1.0' encoding='UTF-8'?>
   <root>
      <node name="foo1" value="bar1" />
      <node name="foo2" value="bar2" />
   </root>

I have a method

String processBar(String bar)

and I want to end up with

<?xml version='1.0' encoding='UTF-8'?>
   <root>
      <node name="foo1" value="processBar("bar1")" />
      <node name="foo2" value="processBar("bar2")" />
   </root>

Is there an easy way to do this? Preferably in Java. Note that the file is too large to safely load completely into memory. The data in the XML roughly arbitrary and processBar may be complex, so I don't want to use regular expressions.

Answer 1

you can either parse the whole thing in a java xml parser OR just get the file content into a string and then do a regexp replace on it (using i.e. http://java.sun.com/j2se/1.5.0/docs/api/java/lang/String.html#replaceAll%28java.lang.String,%20java.lang.String%29)

Answer 2

Assuming you mean replacing the attribute values with the result of calling processBar on said attribute values...

Use the JDK's XSLT API to run the following:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" 
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:java="http://xml.apache.org/xalan/java"
                extension-element-prefixes="java">
  <xsl:template match="/root/node/@value">
    <xsl:attribute name="value">
      <xsl:value-of select="java:com.example.yourclass.processBar(string(.))"/>
    </xsl:attribute>
  </xsl:template>
</xsl:stylesheet>

This uses the Xalan-Java extensions and assumes a static method. You can get an instance of an object and store it in an xsl:variable, like this:

<xsl:variable name="frobber" select="java:com.example.Frobber.new()"/>
<xsl:value-of select="java:processBar($frobber, string(.))"/>

Or somesuch.

This only works with Xalan, but since that's the XSLT processor distributed with the JDK, I doubt it will be onerous to use Xalan.