fop/examples/embedding/java/embedding/events/ExampleEvents.java

/*
 * 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.
 */

/* $Id$ */

package embedding.events;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URL;

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.sax.SAXResult;
import javax.xml.transform.stream.StreamSource;

import org.xml.sax.SAXException;

import org.apache.commons.io.IOUtils;

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;
import org.apache.fop.events.Event;
import org.apache.fop.events.EventFormatter;
import org.apache.fop.events.EventListener;
import org.apache.fop.events.model.EventSeverity;

/**
 * This class demonstrates how to register an event listener with FOP so you can customize
 * FOP's error behaviour.
 */
public class ExampleEvents {

    // configure fopFactory as desired
    private FopFactory fopFactory = FopFactory.newInstance();

    /**
     * Converts an FO file to a PDF file using FOP
     * @param fo the FO file
     * @param pdf the target PDF file
     * @throws IOException In case of an I/O problem
     * @throws FOPException In case of a FOP problem
     * @throws TransformerException In case of a problem with XSLT
     */
    public void convertFO2PDF(URL fo, File pdf)
            throws IOException, FOPException, TransformerException {

        OutputStream out = null;

        try {
            //Create the user agent for this processing run
            FOUserAgent foUserAgent = fopFactory.newFOUserAgent();

            //Adding a simple logging listener that writes to stdout and stderr
            foUserAgent.getEventBroadcaster().addEventListener(new SysOutEventListener());

            // Add your own event listener
            foUserAgent.getEventBroadcaster().addEventListener(new MyEventListener());

            // configure foUserAgent further as desired

            // Setup output stream.  Note: Using BufferedOutputStream
            // for performance reasons (helpful with FileOutputStreams).
            out = new FileOutputStream(pdf);
            out = new BufferedOutputStream(out);

            // Construct fop with desired output format
            Fop fop = fopFactory.newFop(MimeConstants.MIME_PDF, foUserAgent, out);

            // Setup JAXP using identity transformer
            TransformerFactory factory = TransformerFactory.newInstance();
            Transformer transformer = factory.newTransformer(); // identity transformer

            // Setup input stream
            Source src = new StreamSource(fo.toExternalForm());

            // Resulting SAX events (the generated FO) must be piped through to FOP
            Result res = new SAXResult(fop.getDefaultHandler());

            // Start XSLT transformation and FOP processing
            transformer.transform(src, res);

        } finally {
            IOUtils.closeQuietly(out);
        }
    }

    private static class MyEventListener implements EventListener {

        public void processEvent(Event event) {
            if ("org.apache.fop.events.ResourceEventProducer.imageNotFound"
                    .equals(event.getEventID())) {

                //Get the FileNotFoundException that's part of the event's parameters
                FileNotFoundException fnfe = (FileNotFoundException)event.getParam("fnfe");

                System.out.println("---=== imageNotFound Event for " + event.getParam("uri")
                        + "!!! ===---");
                //Stop processing when an image could not be found. Otherwise, FOP would just
                //continue without the image!

                System.out.println("Throwing a RuntimeException...");
                throw new RuntimeException(EventFormatter.format(event), fnfe);
            } else {
                //ignore all other events
            }
        }

    }

    /** A simple event listener that writes the events to stdout and sterr. */
    private static class SysOutEventListener implements EventListener {

        /** {@inheritDoc} */
        public void processEvent(Event event) {
            String msg = EventFormatter.format(event);
            EventSeverity severity = event.getSeverity();
            if (severity == EventSeverity.INFO) {
                System.out.println("[INFO ] " + msg);
            } else if (severity == EventSeverity.WARN) {
                System.out.println("[WARN ] " + msg);
            } else if (severity == EventSeverity.ERROR) {
                System.err.println("[ERROR] " + msg);
            } else if (severity == EventSeverity.FATAL) {
                System.err.println("[FATAL] " + msg);
            } else {
                assert false;
            }
        }
    }


    /**
     * This method extracts the original exception from some exception. The exception
     * might be nested multiple levels deep.
     * @param t the Throwable to inspect
     * @return the original Throwable or the method parameter t if there are no nested Throwables.
     */
    private static Throwable getOriginalThrowable(Throwable t) {
        if (t instanceof SAXException) {
            SAXException saxe = (SAXException)t;
            if (saxe.getException() != null) {
                return getOriginalThrowable(saxe.getException());
            } else {
                return saxe;
            }
        } else {
            if (t.getCause() != null) {
                return getOriginalThrowable(t.getCause());
            } else {
                return t;
            }
        }
    }

    /**
     * Main method.
     * @param args command-line arguments
     */
    public static void main(String[] args) {
        try {
            System.out.println("FOP ExampleEvents\n");
            System.out.println("Preparing...");

            //Setup directories
            File baseDir = new File(".");
            File outDir = new File(baseDir, "out");
            outDir.mkdirs();

            //Setup input and output files
            URL fo = ExampleEvents.class.getResource("missing-image.fo");
            File pdffile = new File(outDir, "out.pdf");

            System.out.println("Input: XSL-FO (" + fo.toExternalForm() + ")");
            System.out.println("Output: PDF (" + pdffile + ")");
            System.out.println();
            System.out.println("Transforming...");

            ExampleEvents app = new ExampleEvents();

            try {
                app.convertFO2PDF(fo, pdffile);
            } catch (TransformerException te) {
                //Note: We don't get the original exception here!
                //FOP needs to embed the exception in a SAXException and the TraX transformer
                //again wraps the SAXException in a TransformerException. Even our own
                //RuntimeException just wraps the original FileNotFoundException.
                //So we need to unpack to get the original exception (about three layers deep).
                Throwable originalThrowable = getOriginalThrowable(te);
                originalThrowable.printStackTrace(System.err);
                System.out.println("Aborted!");
                System.exit(-1);
            }

            System.out.println("Success!");
        } catch (Exception e) {
            //Some other error (shouldn't happen in this example)
            e.printStackTrace(System.err);
            System.exit(-1);
        }
    }

}