Servlets

Here is a minimal code snippet to demonstrate the basics:

public void doGet(HttpServletRequest request,
                   HttpServletResponse response) throws ServletException {
    try {
        response.setContentType("application/pdf");
        Driver driver = new Driver(new InputSource("foo.fo"),
                                   response.getOutputStream());
        driver.setRenderer(Driver.RENDER_PDF);
        driver.run();
    } catch (Exception ex) {
        throw new ServletException(ex);
    }
}

A common requirement is the to transform an XML source to XSLFO using an XSL transformation. It is recommended to use JAXP for this task. The following snippet shows the basic code:

protected Logger log;
protected TransformerFactory transformerFactory;

public void init() throws ServletException {
    this.log = new ConsoleLogger(ConsoleLogger.LEVEL_WARN);
    this.transformerFactory = TransformerFactory.newInstance();
}

[..]

    //Setup FOP
    Driver driver = new Driver();
    driver.setLogger(this.log);
    driver.setRenderer(Driver.RENDER_PDF);

    //Setup a buffer to obtain the content length
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    driver.setOutputStream(out);

    //Setup Transformer
    Source xsltSrc = new StreamSource(new File("foo-xml2fo.xsl"));
    Transformer transformer = this.transformerFactory.newTransformer(xsltSrc);

    //Make sure the XSL transformation's result is piped through to FOP
    Result res = new SAXResult(driver.getContentHandler());

    //Setup input
    Source src = new StreamSource(new File("foo.xml"));

    //Start the transformation and rendering process
    transformer.transform(src, res);

    //Prepare response
    response.setContentType("application/pdf");
    response.setContentLength(out.size());
    
    //Send content to Browser
    response.getOutputStream().write(out.toByteArray());
    response.getOutputStream().flush();

The Source instance used above is simply an example. If you have to read the XML from a string, supply a new StreamSource(new StringReader(xmlstring)). Constructing and reparsing an XML string is generally less desirable than using a SAXSource if you generate your XML. You can alternatively supply a DOMSource as well. You may also use dynamically generated XSL if you like.

Because you have an explicit Transformer object, you can also use it to explicitly set parameters for the transformation run.

If you need to supply a special configuration do this in the init() method so it will only be done once and to avoid multithreading problems.

public void init() throws ServletException {
    [..]
    new Options(new File("userconfig.xml"));
    //or
    Configuration.put("baseDir", "/my/base/dir");
}

There are several options to consider:

• Instead of java.io.ByteArrayOutputStream consider using the ByteArrayOutputStream implementation from the Jakarta Commons IO project which allocates less memory.
• In certain cases it can help to write the generated PDF to a temporary file so you can quickly reuse the file. This is especially useful, if Internet Explorer calls the servlet multiple times with the same request or if you often generate equal PDFs.

Of course, the performance hints from the Embedding page apply here, too.

Check Tomcat's documentation for detailed instructions about installing FOP and Cocoon. There are known bugs that must be addressed, particularly for Tomcat 4.0.3.

Put a copy of a working parser in some directory where WebSphere can access it. For example, if /usr/webapps/yourapp/servlets is the CLASSPATH for your servlets, copy the Xerces jar into it (any other directory would also be fine). Do not add the jar to the servlet CLASSPATH, but add it to the CLASSPATH of the application server which contains your web application. In the WebSphere administration console, click on the "environment" button in the "general" tab. In the "variable name" box, enter "CLASSPATH". In the "value" box, enter the correct path to the parser jar file (/usr/webapps/yourapp/servlets/Xerces.jar in our example here). Press "OK", then apply the change and restart the application server.