PHP & Java(3)

Example 2: Using Xalan 1.2 to transform XML with XSLT

As another example of accessing Java objects in PHP, we will use the Xalan-java XSLT engine from the Apache XML project. With this application, we can transform XML source files using instructions in a XSL file. This allows for a great number of interesting scenarios in the field of document processing and content management.

To get started, we need to place both xerces.jar and xalan.jar files (included in Xalan-Java version 1.2 from xml.apache.org) in your java.class.path, as defined in your php.ini file.

The function xslt_transform() takes XML and XSL files as parameters and returns the transformed output in a string. XML and XSL parameters can be filenames (eg. foo.xml) or fully resolved URI's (eg. http://localhost/foo.xml).

<?php

function xslt_transform($xml,$xsl) {

    // Create a XSLTProcessorFactory object. XSLTProcessorfactory is a Java
    // class which manufactures the processor for performing transformations.
    $XSLTProcessorFactory = new java("org.apache.xalan.xslt.XSLTProcessorFactory"); 

    // Use the XSLTProcessorFactory method getProcessor() to create a
    // new XSLTProcessor object.
    $XSLTProcessor = $XSLTProcessorFactory->getProcessor();

    // Use XSLTInputSource objects to provide input to the XSLTProcessor 
    // process() method for transformation. Create objects for both the
    // xml source as well as the XSL input source. Parameter of 
    // XSLTInputSource is (in this case) a 'system identifier' (URI) which
    // can be an URL or filename. If the system identifier is an URL, it
    // must be fully resolved.
    $xmlID = new java("org.apache.xalan.xslt.XSLTInputSource", $xml);
    $stylesheetID = new java("org.apache.xalan.xslt.XSLTInputSource", $xsl);

    // Create a stringWriter object for the output. 
    $stringWriter = new java("java.io.StringWriter");

    // Create a ResultTarget object for the output with the XSLTResultTarget
    // class. Parameter of XSLTResultTarget is (in this case) a 'character
    // stream', which is the stringWriter object.  
    $resultTarget = new java("org.apache.xalan.xslt.XSLTResultTarget", $stringWriter);

    // Process input with the XSLTProcessors' method process(). This 
    // method uses the XSL stylesheet to transform the XML input, placing
    // the result in the result target.
    $XSLTProcessor->process($xmlID,$stylesheetID,$resultTarget);

    // Use the stringWriters' method toString() to
    // return the buffer's current value as a string to get the
    // transformed result.
    $result = $stringWriter->toString();
    $stringWriter->close();
    return($result);
}

?>

Then, you can call this function as shown in the example below. $xml contains a string with the fully resolved URL of XML file. $xsl contains string with a XSL stylesheet URL containing rules for conversion to generic HTML. $out will contain a string with output, as a result of calling xslt_transform described above. This example parses a XML newsfeed containing the 5 latest articles on phpbuilder.com. You are encouraged to also try other XML feeds and/or XSl stylesheets.

<?php

$xml = "http://www.phpbuilder.com/rss_feed.php?type=articles&limit=5";
$xsl = "http://www.soeterbroek.com/code/xml/rss_html.xsl";
$out = xslt_transform($xml,$xsl);
echo $out;

?>

If you are processing local files, make sure you use the full path name to pass to the Java class.

<?php

$xml    = "/web/htdocs/xml_java/rss_feed.xml";
$xsl    = "/web/htdocs/xml_java/rss_html.xsl";
$out = xslt_transform($xml,$xsl);
echo $out;

?>

Although there are a number of other ways in PHP to achieve the same results, the above example gives you a good idea of the possibilities of accessing Java objects in PHP.