source: AE/installer2/src/net/oni2/aeinstaller/backend/network/FileDownloader.java@ 603

package net.oni2.aeinstaller.backend.network;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.net.URL;
import java.net.URLConnection;
import java.util.HashSet;

/**
 * @author Christian Illy
 */
public class FileDownloader implements Runnable {
        /**
         * @author Christian Illy
         */
        public enum EState {
                /**
                 * Downloader initialized but not started
                 */
                INIT,
                /**
                 * Download running
                 */
                RUNNING,
                /**
                 * Download suspended
                 */
                PAUSED,
                /**
                 * Download interrupted
                 */
                INTERRUPTED,
                /**
                 * Download finished successfully
                 */
                FINISHED,
                /**
                 * Aborted because of an error
                 */
                ERROR
        };

        private HashSet<FileDownloadListener> listeners = new HashSet<FileDownloadListener>();
        private Thread t = null;
        private URL url = null;
        private File target = null;
        private int size = -1;
        private int downloaded = 0;

        private EState state = EState.INIT;

        /**
         * @param url
         *            URL of file to download
         * @param target
         *            Path of target file to save to
         * @throws IOException
         *             If url could not be opened
         */
        public FileDownloader(String url, String target) throws IOException {
                this.url = new URL(url);
                this.target = new File(target);

                URLConnection connection = this.url.openConnection();
                connection.connect();
                size = connection.getContentLength();
        }

        /**
         * @param listener
         *            Listener to add
         */
        public void addListener(FileDownloadListener listener) {
                listeners.add(listener);
        }

        /**
         * @param listener
         *            Listener to remove
         */
        public void removeListener(FileDownloadListener listener) {
                listeners.remove(listener);
        }

        /**
         * Start the download process
         */
        public synchronized void start() {
                if (t == null) {
                        t = new Thread(this);
                        t.start();
                        state = EState.RUNNING;
                }
        }

        /**
         * @param suspend
         *            Suspend or resume
         */
        public synchronized void suspend(boolean suspend) {
                if ((state == EState.RUNNING) || (state == EState.PAUSED)) {
                        if (suspend)
                                state = EState.PAUSED;
                        else
                                state = EState.RUNNING;
                }
        }

        /**
         * Stop (abort) download
         */
        public synchronized void stop() {
                state = EState.INTERRUPTED;
                try {
                        t.join();
                } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                }
                updateStatus(0, 1);
                t = null;
                if (target.exists())
                        target.delete();
        }

        private synchronized void updateStatus(int current, int total) {
                downloaded = current;
                for (FileDownloadListener l : listeners) {
                        l.statusUpdate(this, state, current, total);
                }
        }

        @Override
        public void run() {
                int downloaded = 0;
                int fileLength = Integer.MAX_VALUE;
                String strLastModified = null;
                String strEtag = null;
                RandomAccessFile outFile = null;
                try {
                        outFile = new RandomAccessFile(target, "rw");
                } catch (FileNotFoundException e1) {
                        // TODO Auto-generated catch block
                        e1.printStackTrace();
                        state = EState.ERROR;
                        return;
                }

                while (downloaded < fileLength) {
                        switch (state) {
                                case ERROR:
                                        updateStatus(downloaded, fileLength);
                                        return;
                                case PAUSED:
                                        try {
                                                Thread.sleep(100);
                                        } catch (InterruptedException e) {
                                                e.printStackTrace();
                                        }
                                        break;
                                case INTERRUPTED:
                                        return;
                                case RUNNING:
                                        BufferedInputStream input = null;
                                        try {
                                                URLConnection connection = url.openConnection();
                                                if (downloaded == 0) {
                                                        connection.connect();
                                                        strLastModified = connection
                                                                        .getHeaderField("Last-Modified");
                                                        strEtag = connection.getHeaderField("ETag");
                                                        fileLength = connection.getContentLength();
                                                } else {
                                                        connection.setRequestProperty("Range", "bytes="
                                                                        + downloaded + "-");
                                                        if (strEtag != null)
                                                                connection.setRequestProperty("If-Range",
                                                                                strEtag);
                                                        else
                                                                connection.setRequestProperty("If-Range",
                                                                                strLastModified);
                                                        connection.connect();
                                                }

                                                // Setup streams and buffers.
                                                input = new BufferedInputStream(
                                                                connection.getInputStream(), 8192);
                                                if (downloaded > 0)
                                                        outFile.seek(downloaded);
                                                byte data[] = new byte[1024];

                                                // Download file.
                                                int dataRead = 0;
                                                int i = 0;
                                                while (((dataRead = input.read(data, 0, 1024)) != -1)
                                                                && (state == EState.RUNNING)) {
                                                        outFile.write(data, 0, dataRead);
                                                        downloaded += dataRead;
                                                        if (downloaded >= fileLength)
                                                                break;

                                                        i++;
                                                        if ((i % 10) == 0)
                                                                updateStatus(downloaded, fileLength);
                                                }
                                                input.close();
                                        } catch (IOException e) {
                                                // TODO Auto-generated catch block
                                                e.printStackTrace();
                                                try {
                                                        if (input != null)
                                                                input.close();
                                                } catch (IOException e2) {
                                                        e2.printStackTrace();
                                                }
                                        }
                                        break;
                                default:
                                        break;
                        }
                }

                try {
                        // Close streams.
                        outFile.close();
                } catch (IOException e) {
                        e.printStackTrace();
                }

                state = EState.FINISHED;
                updateStatus(downloaded, fileLength);
        }

        /**
         * @return the target
         */
        public File getTarget() {
                return target;
        }

        /**
         * @return the size
         */
        public int getSize() {
                return size;
        }

        /**
         * @return the downloaded size
         */
        public int getDownloaded() {
                return downloaded;
        }

}