Raible's Wiki: POJOToPDF

The FOP process I am going to describe is producing XML from a POJO entity, passing that XML through an XSL stylesheet to produce a FO XML document, then passing the FO document through an XSLT processor to produce the PDF document.

Please note, the resulting PDF document does not look very pretty. This is because the XSL stylesheet is very basic and does not really apply much FO formatting tags/attributes. It would be very easy to modify the XSL to include images, bold, grey background cells etc.. but this is best left for the FOP documentation to describe.

Create an InputSource for your POJO [#1]

In src/service/**/fop, create a UserInputSource.java file with the following contents:

Create XMLReader for your User POJO [#2]

Now we need to create the XMLReader which will generate SAX events from our User object. This object should write any data from the User object, we might want to publish in our PDF document.

This class depends on two helper classes, AbstractObjectReader and EasyGenerationContentHandlerProxy that need to be added to src/service/**/util. These files are downloadable at the end of this tutorial.




package org.appfuse.fop;



//Java

import java.io.IOException;

import java.util.Iterator;

import java.util.Set;



//SAX

import org.xml.sax.InputSource;

import org.xml.sax.SAXException;



import org.apache.log4j.Logger;



// Appfuse imports

import org.appfuse.model.User;

import org.appfuse.model.Role;

import org.appfuse.util.AbstractObjectReader;



/**

 * XMLReader implementation for the User class. This class is used to

 * generate SAX events from the User class.

 */

public class UserXMLReader extends AbstractObjectReader {



    // User elements

    public static final String USER = "user";

    public static final String FIRST_NAME = "firstName";

    public static final String LAST_NAME = "lastName";

  

    // Role elements

    public static final String ROLE = "role";

    public static final String ROLE_NAME = "roleName";

  

    protected Logger log = Logger.getLogger(getClass());



    /**

     * @see org.xml.sax.XMLReader#parse(InputSource)

     */

    public void parse(InputSource input) throws IOException, SAXException {

        if (input instanceof UserInputSource) {

            parse(((UserInputSource)input).getUser());

        } else {

            throw new SAXException("Unsupported InputSource specified. Must be a UserInputSource");

        }

    }

    

    /**

     * Starts parsing the User object.

     * @param user The object to parse

     * @throws SAXException In case of a problem during SAX event generation

     */

    public void parse(User user) throws SAXException {

        if (user == null) {

            throw new NullPointerException("Parameter user must not be null");

        }

        if (handler == null) {

            throw new IllegalStateException("ContentHandler not set");

        }

        

        //Start the document

        handler.startDocument();

        

        //Generate SAX events for the User

        processUser(user);

        

        //End the document

        handler.endDocument();        

    }

    

    /**

     * Generates SAX events for a User object.

     * @param user User object to use

     * @throws SAXException In case of a problem during SAX event generation

     */

    protected void processUser(User user) throws SAXException {

        if (user == null) {

            throw new NullPointerException("Parameter user must not be null");

        }

        if (handler == null) {

            throw new IllegalStateException("ContentHandler not set");

        }

        

        handler.startElement(USER);



  processUserDetails(user);

        processRoles(user);

        

        handler.endElement(USER);

    }

    

    protected void processUserDetails(User user) throws SAXException {



        handler.element(FIRST_NAME, user.getFirstName());

        handler.element(LAST_NAME, user.getLastName());

    }



    protected void processRoles(User user) throws SAXException {

      

      Set roles = user.getRoles();

      

      if (roles!=null) {



        Iterator iter = roles.iterator();

        

        while (iter.hasNext()) {

          

          Role role = (Role)iter.next();

            handler.startElement(ROLE);

            handler.element(ROLE_NAME, role.getName());

            handler.endElement(ROLE);

        }

      }

    }

}

Create XSL stylesheet to produce FO [#3]

The xsl stylesheet will process the XML generated by the UserXMLReader and produce a FO document. The FO document is processed by Apache FOP to produce the PDF document. Therefore, the XSL stylesheet is where we can modify the FO formatting and style the PDF document.

Modify User Junit test [#4]

To support the execution of the User service level test, we need another helper file. This file (attached at the end) is called FOPHelper.java and lives in src/service/**/utils.




import java.io.File;

import java.io.OutputStream;

import java.io.IOException;



//JAXP

import javax.xml.transform.Transformer;

import javax.xml.transform.TransformerFactory;

import javax.xml.transform.TransformerException;

import javax.xml.transform.Source;

import javax.xml.transform.Result;

import javax.xml.transform.stream.StreamSource;

import javax.xml.transform.sax.SAXResult;



//Avalon

import org.apache.avalon.framework.ExceptionUtil;

import org.apache.avalon.framework.logger.ConsoleLogger;

import org.apache.avalon.framework.logger.Logger;



//FOP

import org.apache.fop.apps.Driver;

import org.apache.fop.apps.FOPException;

import org.apache.fop.messaging.MessageHandler;



//Appfuse

import org.appfuse.fop.UserInputSource;

import org.appfuse.utils.FOPHelper;





    public void testGeneratePDF() throws Exception {



        try {

            User testData = new User();

            testData.setUsername("tomcat");

            testData.getRoles().add(new Role("user"));

            // set expected behavior on dao

            userDAO.expects(once()).method("getUser")

               .with(eq("tomcat")).will(returnValue(testData));



            user = userManager.getUser("tomcat");



            File baseDir = new File(".");

            File xslFile = new File(baseDir, "./src/web/org/appfuse/webapp/fop/user2fo.xsl");

            if (xslFile.exists()) {

                log.info("xslFile exists");

            }

            File pdfFile = new File(baseDir, "user.pdf");

            File xmlFile = new File(baseDir, "user.xml");



            log.debug("Input: a User object");

            log.debug("Stylesheet: " + xslFile);

            log.debug("Output: PDF (" + pdfFile + ")");

            log.debug("Transforming...");



            FOPHelper fopHelper = new FOPHelper();

            fopHelper.convertUser2PDF(user, xslFile, pdfFile);

            fopHelper.convertUser2XML(user, xmlFile);



        }

        catch (Throwable e) {

            log.error("Error [" + e.getMessage() + "]", e);

        }

    }

Run User Junit test [#5]

Now execute ant test-service. The testGeneratePDF method will execute and generate the 3 files involved in the PDF generation process. user.xml, user.fo and user.pdf (all three attached at the end of this tutorial).

Create a servlet to handle the requests [#6]

This servlet will take a userName from the HttpRequest object, call the UserDAO to load a User. It then calls UserXmlReader to generate the XML, does the XSLT transformation, and generates the PDF document. During this process, no files are saved to disk.




package org.appfuse.webapp.action;



import org.appfuse.model.User;

import org.appfuse.dao.UserDAO;

import org.appfuse.fop.UserInputSource;



import org.apache.avalon.framework.logger.ConsoleLogger;

import org.apache.avalon.framework.logger.Logger;

import org.apache.fop.apps.Driver;

import org.apache.fop.apps.XSLTInputHandler;

import org.apache.fop.apps.TraxInputHandler;

import org.apache.fop.messaging.MessageHandler;



import java.io.ByteArrayOutputStream;

import java.io.File;

import java.io.IOException;



import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;



import org.springframework.context.ApplicationContext;

import org.springframework.web.context.support.WebApplicationContextUtils;

import org.springframework.web.context.support.ServletContextResource;



import javax.xml.transform.Result;

import javax.xml.transform.Source;

import javax.xml.transform.Transformer;

import javax.xml.transform.TransformerFactory;

import javax.xml.transform.sax.SAXResult;

import javax.xml.transform.stream.StreamSource;



/**

 * Implementation of <strong>HttpServlet</strong> that is used

 * to autogenerate a PDF document.

 *

 * <p><a href="FopServlet.java.html"><i>View Source</i></a></p>

 *

 * @author <a href="mailto:mailto:[email protected]">Ben Gill</a>

 * @version $Revision: 1.1 $ $Date: 2005/03/12 17:46:09 $

 *

 * @web.servlet

 *     display-name="Fop Servlet"

 *     load-on-startup="1"

 *     name="fop"

 *

 * @web.servlet-mapping

 *     url-pattern="/fop/*"

 */



public class FopServlet extends HttpServlet {

  

    private Logger logger = null;    

    private ApplicationContext ctx = null;

    private ServletContext servletContext = null;

    



    public void init() throws ServletException {

      this.servletContext = getServletContext();

      this.ctx =  

        WebApplicationContextUtils.getRequiredWebApplicationContext(servletContext);

    }



    /**

     * Route the user to the execute method

     *

     * @param request The HTTP request we are processing

     * @param response The HTTP response we are creating

     *

     * @exception IOException if an input/output error occurs

     * @exception ServletException if a servlet exception occurs

     */

    public void doGet(HttpServletRequest request, HttpServletResponse response)

        throws IOException, ServletException {

        execute(request, response);

    }



    /**

     * Route the user to the execute method

     *

     * @param request The HTTP request we are processing

     * @param response The HTTP response we are creating

     *

     * @exception IOException if an input/output error occurs

     * @exception ServletException if a servlet exception occurs

     */

    public void doPost(HttpServletRequest request, HttpServletResponse response)

        throws IOException, ServletException {

        execute(request, response);

    }



    /**

     * Process the specified HTTP request, and create the corresponding HTTP

     * response (or forward to another web component that will create it).

     *

     * @param request The HTTP request we are processing

     * @param response The HTTP response we are creating

     *

     * @exception IOException if an input/output error occurs

     * @exception ServletException if a servlet exception occurs

     */

    public void execute(HttpServletRequest request, HttpServletResponse response)

        throws IOException, ServletException {

      

      ByteArrayOutputStream out = null;

      

      try {

            String userName = request.getParameter("userName");

          

            UserDAO dao = (UserDAO)ctx.getBean("userDAO");

            User user = dao.getUser(userName);

            

            Driver driver = new Driver();

            Logger logger = new ConsoleLogger(ConsoleLogger.LEVEL_INFO);

            driver.setLogger(logger);

            MessageHandler.setScreenLogger(logger);

            driver.setRenderer(Driver.RENDER_PDF);





            // Start with a bigger buffer to avoid too many buffer reallocations

            out = new ByteArrayOutputStream(16384);

            driver.setOutputStream(out);



            ServletContextResource resource = 

                new ServletContextResource(servletContext, 

                "/WEB-INF/classes/org/appfuse/webapp/fop/user2fo.xsl");

            File xslFile = resource.getFile();

            

            //Setup XSLT

            TransformerFactory factory = TransformerFactory.newInstance();

            Transformer transformer = factory.newTransformer(new StreamSource(xslFile));

        

            //Setup input for XSLT transformation

            Source src = new UserInputSource(user).getSource();

        

            //Resulting SAX events (the generated FO) must be piped through to FOP

            Result res = new SAXResult(driver.getContentHandler());



            //Start XSLT transformation and FOP processing

            transformer.transform(src, res);

            

            byte[] content = out.toByteArray();

            response.setContentType("application/pdf");

            response.setContentLength(content.length);

            response.getOutputStream().write(content);

            response.getOutputStream().flush();

            

        } catch (Exception e) {

            throw new ServletException(e);

        } finally {

          if (out!=null) {

            out.close();

          }

        }

    }

}

Modify JSP to call the servlet [#7]

To link to the servlet from the main app. Add the following column to the table in src/web/pages/userList.jsp:

Environment changes needed [#8]

You need to download and install fop-0.20.5

into the appfuse lib structure. Ensure these jar files are in your lib/fop-0.20.5 dir:

Troubleshooting [#9]

If you follow these instructions, things should work fine. But here are things to check if it is not working for you:

Raible's Wiki

AppFuse

Other Applications

POJOToPDF

About this Tutorial

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