IBM Version 5 manual Example 10-2 Source code for CustomerXSLServlet init method

}

￿CustomerXSLServlet: This is responsible for applying the XSL to the DOM generated from the CustomerXML. This process transforms and formats the DOM information into a rendered result. This is called styling. For the styling to be possible, two components come together: XSL Transormations (XSLT), which allows for a reorganization of information; and XSL, which specifies the formatting of the information for rendering. A XSL processor takes a stylesheet consisting of a set of XSL commands, and transforms an input XML document. Studying the code for this servlet, we noticed the following:

–The init method does the necessary configuration and initialization for the sevlet's operation. For the servlet to handle the process of transforming the XML data to the desirable format, based on an XSL stylesheet, the servlet needs to do some configuration steps before invoking the XSLT processor. The init method first creates a new instance of the TransformerFactory class.

–Having the stylesheet XSL files present in the file system, the Transformer factory instance needs to reference them. So the servlet creates the template’s objects using the XSL files. A template’s object is a compiled representation of a XSL file. Compilation of XSL is provided by JAXP. Invoking the newTemplates method of the TransformerFactory, and passing to it an XSL file, it processes the file, and generates a compiled representation of that XSL file in the form of the template’s object.

–This template’s object may then be used concurrently across multiple threads. Creating a templates object allows the TransformerFactory to do detailed performance optimization of transformation instructions, without penalizing runtime transformation. As shown in Example 10-2, the init method retrieves the files using the path specifies in the begining of the method, and creates the template’s objects using the transformer factory. The XSLT processor should used these compiled instances of the style sheets to transform a XML document. Exceptions are thrown if the servlet cannot locate the XSL files in the specified location, or if the files contain errors.

Example 10-2 Source code for CustomerXSLServlet init method

public void init(ServletConfig config) throws ServletException

{super.init(config); TransformerFactory transFact =

TransformerFactory.newInstance(); String xslName = "/WEB-INF/xsl/Customer.xsl";

String xslResult = "/WEB-INF/xsl/CustomerResult.xsl"; try

{URL stylesheetURL =

230 The XML Files: Development of XML/XSL Applications Using WebSphere Studio