http://xmlgraphics.apache.org/fop/: Apache FOP (Formatting Objects Processor) is the world's first print formatter driven by XSL formatting objects (XSL-FO) and the world's first output independent formatter. It is a Java application that reads a formatting object (FO) tree and renders the resulting pages to a specified output. Output formats currently supported include PDF, PCL, PS, AFP, TIFF, PNG, SVG, XML (area tree representation), Print, AWT and TXT. The primary output target is PDF. (Apache Software Foundation) 
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/* $Id: FopServlet.java 1805173 2017-08-16 10:50:04Z ssteiner $ */

package org.apache.fop.servlet;

import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.URI;
import java.net.URL;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.URIResolver;
import javax.xml.transform.sax.SAXResult;
import javax.xml.transform.stream.StreamSource;

import org.apache.commons.io.output.ByteArrayOutputStream;

import org.apache.xmlgraphics.io.Resource;
import org.apache.xmlgraphics.io.ResourceResolver;

import org.apache.fop.apps.FOPException;
import org.apache.fop.apps.FOUserAgent;
import org.apache.fop.apps.Fop;
import org.apache.fop.apps.FopFactory;
import org.apache.fop.apps.FopFactoryBuilder;
import org.apache.fop.apps.MimeConstants;


Example servlet to generate a PDF from a servlet.


Servlet param is:

    
  
  • fo: the path to a XSL-FO file to render


or

    
  
  • xml: the path to an XML file to render
    • 
  
  • xslt: the path to an XSLT file that can transform the above XML to XSL-FO
    • 




Example URL: http://servername/fop/servlet/FopServlet?fo=readme.fo


Example URL: http://servername/fop/servlet/FopServlet?xml=data.xml


For this to work with Internet Explorer, you might need to append "ext=.pdf"
to the URL.
(todo) Ev. add caching mechanism for Templates objects

/**
 * Example servlet to generate a PDF from a servlet.
 * <br>
 * Servlet param is:
 * <ul>
 *   <li>fo: the path to a XSL-FO file to render
 * </ul>
 * or
 * <ul>
 *   <li>xml: the path to an XML file to render</li>
 *   <li>xslt: the path to an XSLT file that can transform the above XML to XSL-FO</li>
 * </ul>
 * <br>
 * Example URL: http://servername/fop/servlet/FopServlet?fo=readme.fo
 * <br>
 * Example URL: http://servername/fop/servlet/FopServlet?xml=data.xml
 * <br>
 * For this to work with Internet Explorer, you might need to append "ext=.pdf"
 * to the URL.
 * (todo) Ev. add caching mechanism for Templates objects
 */
public class FopServlet extends HttpServlet {

    private static final long serialVersionUID = -908918093488215264L;

    
Name of the parameter used for the XSL-FO file 
/** Name of the parameter used for the XSL-FO file */
    protected static final String FO_REQUEST_PARAM = "fo";
    
Name of the parameter used for the XML file 
/** Name of the parameter used for the XML file */
    protected static final String XML_REQUEST_PARAM = "xml";
    
Name of the parameter used for the XSLT file 
/** Name of the parameter used for the XSLT file */
    protected static final String XSLT_REQUEST_PARAM = "xslt";

    
The TransformerFactory used to create Transformer instances 
/** The TransformerFactory used to create Transformer instances */
    protected TransformerFactory transFactory;
    
The FopFactory used to create Fop instances 
/** The FopFactory used to create Fop instances */
    protected FopFactory fopFactory;
    
URIResolver for use by this servlet 
/** URIResolver for use by this servlet */
    protected transient URIResolver uriResolver;

    
{@inheritDoc}

/**
     * {@inheritDoc}
     */
    public void init() throws ServletException {
        this.uriResolver = new ServletContextURIResolver(getServletContext());
        this.transFactory = TransformerFactory.newInstance();
        transFactory.setAttribute("http://javax.xml.XMLConstants/property/accessExternalDTD", "");
        transFactory.setAttribute("http://javax.xml.XMLConstants/property/accessExternalStylesheet", "");
        this.transFactory.setURIResolver(this.uriResolver);
        //Configure FopFactory as desired
        // TODO: Double check this behaves properly!!
        ResourceResolver resolver = new ResourceResolver() {
            public OutputStream getOutputStream(URI uri) throws IOException {
                URL url = getServletContext().getResource(uri.toASCIIString());
                return url.openConnection().getOutputStream();
            }

            public Resource getResource(URI uri) throws IOException {
                return new Resource(getServletContext().getResourceAsStream(uri.toASCIIString()));
            }
        };
        FopFactoryBuilder builder = new FopFactoryBuilder(new File(".").toURI(), resolver);
        configureFopFactory(builder);
        fopFactory = builder.build();
    }

    
This method is called right after the FopFactory is instantiated and can be overridden
by subclasses to perform additional configuration.

/**
     * This method is called right after the FopFactory is instantiated and can be overridden
     * by subclasses to perform additional configuration.
     */
    protected void configureFopFactory(FopFactoryBuilder builder) {
        //Subclass and override this method to perform additional configuration
    }

    
{@inheritDoc}

/**
     * {@inheritDoc}
     */
    public void doGet(HttpServletRequest request,
                      HttpServletResponse response) throws ServletException {
        try {
            //Get parameters
            String foParam = request.getParameter(FO_REQUEST_PARAM);
            String xmlParam = request.getParameter(XML_REQUEST_PARAM);
            String xsltParam = request.getParameter(XSLT_REQUEST_PARAM);

            //Analyze parameters and decide with method to use
            if (foParam != null) {
                renderFO(foParam, response);
            } else if ((xmlParam != null) && (xsltParam != null)) {
                renderXML(xmlParam, xsltParam, response);
            } else {
                response.setContentType("text/html");
                PrintWriter out = response.getWriter();
                out.println("<html><head><title>Error</title></head>\n"
                          + "<body><h1>FopServlet Error</h1><h3>No 'fo' "
                          + "request param given.</body></html>");
            }
        } catch (Exception ex) {
            throw new ServletException(ex);
        }
    }

    
Converts a String parameter to a JAXP Source object.

Params:
  • param – a String parameter
Returns:Source the generated Source object
/**
     * Converts a String parameter to a JAXP Source object.
     * @param param a String parameter
     * @return Source the generated Source object
     */
    protected Source convertString2Source(String param) {
        Source src;
        try {
            src = uriResolver.resolve(param, null);
        } catch (TransformerException e) {
            src = null;
        }
        if (src == null) {
            src = new StreamSource(new File(param));
        }
        return src;
    }

    private void sendPDF(byte[] content, HttpServletResponse response) throws IOException {
        //Send the result back to the client
        response.setContentType("application/pdf");
        response.setContentLength(content.length);
        response.getOutputStream().write(content);
        response.getOutputStream().flush();
    }

    
Renders an XSL-FO file into a PDF file. The PDF is written to a byte
array that is returned as the method's result.

Params:
  • fo – the XSL-FO file
  • response – HTTP response object
Throws:
/**
     * Renders an XSL-FO file into a PDF file. The PDF is written to a byte
     * array that is returned as the method's result.
     * @param fo the XSL-FO file
     * @param response HTTP response object
     * @throws FOPException If an error occurs during the rendering of the
     * XSL-FO
     * @throws TransformerException If an error occurs while parsing the input
     * file
     * @throws IOException In case of an I/O problem
     */
    protected void renderFO(String fo, HttpServletResponse response)
                throws FOPException, TransformerException, IOException {

        //Setup source
        Source foSrc = convertString2Source(fo);

        //Setup the identity transformation
        Transformer transformer = this.transFactory.newTransformer();
        transformer.setURIResolver(this.uriResolver);

        //Start transformation and rendering process
        render(foSrc, transformer, response);
    }

    
Renders an XML file into a PDF file by applying a stylesheet
that converts the XML to XSL-FO. The PDF is written to a byte array
that is returned as the method's result.

Params:
  • xml – the XML file
  • xslt – the XSLT file
  • response – HTTP response object
Throws:
/**
     * Renders an XML file into a PDF file by applying a stylesheet
     * that converts the XML to XSL-FO. The PDF is written to a byte array
     * that is returned as the method's result.
     * @param xml the XML file
     * @param xslt the XSLT file
     * @param response HTTP response object
     * @throws FOPException If an error occurs during the rendering of the
     * XSL-FO
     * @throws TransformerException If an error occurs during XSL
     * transformation
     * @throws IOException In case of an I/O problem
     */
    protected void renderXML(String xml, String xslt, HttpServletResponse response)
                throws FOPException, TransformerException, IOException {

        //Setup sources
        Source xmlSrc = convertString2Source(xml);
        Source xsltSrc = convertString2Source(xslt);

        //Setup the XSL transformation
        Transformer transformer = this.transFactory.newTransformer(xsltSrc);
        transformer.setURIResolver(this.uriResolver);

        //Start transformation and rendering process
        render(xmlSrc, transformer, response);
    }

    
Renders an input file (XML or XSL-FO) into a PDF file. It uses the JAXP
transformer given to optionally transform the input document to XSL-FO.
The transformer may be an identity transformer in which case the input
must already be XSL-FO. The PDF is written to a byte array that is
returned as the method's result.

Params:
  • src – Input XML or XSL-FO
  • transformer – Transformer to use for optional transformation
  • response – HTTP response object
Throws:
/**
     * Renders an input file (XML or XSL-FO) into a PDF file. It uses the JAXP
     * transformer given to optionally transform the input document to XSL-FO.
     * The transformer may be an identity transformer in which case the input
     * must already be XSL-FO. The PDF is written to a byte array that is
     * returned as the method's result.
     * @param src Input XML or XSL-FO
     * @param transformer Transformer to use for optional transformation
     * @param response HTTP response object
     * @throws FOPException If an error occurs during the rendering of the
     * XSL-FO
     * @throws TransformerException If an error occurs during XSL
     * transformation
     * @throws IOException In case of an I/O problem
     */
    protected void render(Source src, Transformer transformer, HttpServletResponse response)
                throws FOPException, TransformerException, IOException {

        FOUserAgent foUserAgent = getFOUserAgent();

        //Setup output
        ByteArrayOutputStream out = new ByteArrayOutputStream();

        //Setup FOP
        Fop fop = fopFactory.newFop(MimeConstants.MIME_PDF, foUserAgent, out);

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

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

        //Return the result
        sendPDF(out.toByteArray(), response);
    }

    
Returns:a new FOUserAgent for FOP
/** @return a new FOUserAgent for FOP */
    protected FOUserAgent getFOUserAgent() {
        FOUserAgent userAgent = fopFactory.newFOUserAgent();
        //Configure foUserAgent as desired
        return userAgent;
    }

}