Java tutorial
/* The contents of this file are subject to the license and copyright terms * detailed in the license directory at the root of the source tree (also * available online at http://fedora-commons.org/license/). */ package fedora.localservices.fop; import java.io.ByteArrayOutputStream; import java.io.File; import java.io.IOException; import java.io.PrintWriter; 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.logging.Log; import org.apache.commons.logging.LogFactory; 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.MimeConstants; /** * Servlet for generating and serving a PDF, given the URL to an XSL-FO file. * * Servlet param is: * <ul> * <li>source: the path to a formatting object file to render * </ul> */ public class FOPServlet extends HttpServlet { private static final long serialVersionUID = 1L; /** Name of the parameter used for the XSL-FO file */ protected static final String FO_REQUEST_PARAM = "source"; /** 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 */ protected static final String XSLT_REQUEST_PARAM = "xslt"; /** Logger to give to FOP */ protected Log log = null; /** The TransformerFactory used to create Transformer instances */ protected TransformerFactory transFactory = null; /** The FopFactory used to create Fop instances */ protected FopFactory fopFactory = null; /** URIResolver for use by this servlet */ protected URIResolver uriResolver = null; /** * {@inheritDoc} */ @Override public void init() throws ServletException { this.log = LogFactory.getLog(FOPServlet.class.getName()); this.uriResolver = new RepositoryURIResolver(); this.transFactory = TransformerFactory.newInstance(); this.transFactory.setURIResolver(this.uriResolver); //Configure FopFactory as desired this.fopFactory = FopFactory.newInstance(); this.fopFactory.setURIResolver(this.uriResolver); configureFopFactory(); } /** * This method is called right after the FopFactory is instantiated and can be overridden * by subclasses to perform additional configuration. */ protected void configureFopFactory() { //Subclass and override this method to perform additional configuration } /** * {@inheritDoc} */ @Override 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); if (foParam != null) { renderFO(foParam, response); } else if ((xmlParam != null) && (xsltParam != null)) { // Note: Not current supported but may be added in a future release. DWD //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 'source' " + "request param given.</body></html>"); } } catch (Exception ex) { throw new ServletException(ex); } } /** * 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. * @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. * @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. * @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); } /** @return a new FOUserAgent for FOP */ protected FOUserAgent getFOUserAgent() { FOUserAgent userAgent = fopFactory.newFOUserAgent(); //Configure foUserAgent as desired return userAgent; } }