Implemented Auto Updating functionality.

Author: jhbruhn

src/de/littlerolf/sav/SortAlgorithmVisualizer.java

@@ -1,5 +1,17 @@
 package de.littlerolf.sav;
 
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.net.URLConnection;
+import java.nio.channels.Channels;
+import java.nio.channels.ReadableByteChannel;
+import java.util.jar.Manifest;
+
 import javax.swing.JFileChooser;
 import javax.swing.JFrame;
 import javax.swing.JOptionPane;
@@ -9,8 +21,105 @@
 import de.littlerolf.sav.gui.SAVFrame;
 
 public class SortAlgorithmVisualizer {
+	private static final String SERVER_URL = "http://littlerolf.github.io/SortAlgorithmVisualizer/";
+
 	public static void main(String[] args) {
-		startLocal();
+		if (isRemoteNewer()) {
+			startJar(downloadRemoteJar().getAbsolutePath());
+		} else
+			startLocal();
+	}
+
+	private static int getLocalVersion() {
+		URLClassLoader cl = (URLClassLoader) SortAlgorithmVisualizer.class
+				.getClassLoader();
+		try {
+			URL url = cl.findResource("META-INF/MANIFEST.MF");
+			Manifest manifest = new Manifest(url.openStream());
+			int version = Integer.valueOf(manifest.getMainAttributes()
+					.getValue("Build-Number"));
+			System.out.println("Local version is " + version + ".");
+			return version;
+
+		} catch (IOException e) {
+			e.printStackTrace();
+		} catch (NullPointerException e) {
+		}
+		return -1;
+	}
+
+	private static int getRemoteVersion() {
+		URL url = null;
+		try {
+			url = new URL(SERVER_URL + "version.txt");
+		} catch (MalformedURLException e2) {
+			e2.printStackTrace();
+		}
+		try {
+			URLConnection urlConnection = url.openConnection();
+			urlConnection.setAllowUserInteraction(false);
+
+			InputStream urlStream = url.openStream();
+			byte buffer[] = new byte[1000];
+			int numRead = urlStream.read(buffer);
+			String content = new String(buffer, 0, numRead);
+
+			while ((numRead != -1) && (content.length() < 1024)) {
+				numRead = urlStream.read(buffer);
+				if (numRead != -1) {
+					String newContent = new String(buffer, 0, numRead);
+					content += newContent;
+				}
+			}
+			content = content.trim();
+			System.out.println("Remote version is " + content + ".");
+
+			return Integer.valueOf(content);
+		} catch (IOException e) {
+			e.printStackTrace();
+		} catch (IndexOutOfBoundsException e1) {
+			e1.printStackTrace();
+		}
+
+		return -1;
+	}
+
+	private static File downloadRemoteJar() {
+		System.out.println("Downloading remote jar.");
+		File f = new File(System.getProperty("user.home") + File.separator
+				+ ".sav" + File.separator + "SAV.jar");
+		f.getParentFile().mkdirs();
+		URL website;
+		try {
+			website = new URL(SERVER_URL + "jar/SAV.jar");
+
+			ReadableByteChannel rbc = Channels.newChannel(website.openStream());
+			FileOutputStream fos = new FileOutputStream(f);
+			fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
+			fos.close();
+			return f;
+
+		} catch (MalformedURLException e) {
+			e.printStackTrace();
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
+		return null;
+	}
+
+	private static boolean isRemoteNewer() {
+		return getRemoteVersion() > getLocalVersion();
+	}
+
+	private static void startJar(String path) {
+		System.out.println("Starting jar " + path + ".");
+		ProcessBuilder pb = new ProcessBuilder("java", "-classpath", path,
+				SortAlgorithmVisualizer.class.getName());
+		try {
+			pb.start();
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
 	}
 
 	private static void startLocal() {