Java tutorial
/*** Copyright (c) 2015 CommonsWare, LLC Licensed 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. Covered in detail in the book _The Busy Coder's Guide to Android Development_ https://commonsware.com/Android */ package com.commonsware.android.webserver; import android.app.Notification; import android.app.PendingIntent; import android.app.Service; import android.content.Intent; import android.content.res.AssetFileDescriptor; import android.content.res.AssetManager; import android.net.ConnectivityManager; import android.net.NetworkInfo; import android.os.IBinder; import android.support.v4.app.NotificationCompat; import android.util.Log; import com.github.jknack.handlebars.Context; import com.github.jknack.handlebars.Handlebars; import com.github.jknack.handlebars.Template; import com.github.jknack.handlebars.io.AbstractTemplateLoader; import com.github.jknack.handlebars.io.StringTemplateSource; import com.github.jknack.handlebars.io.TemplateSource; import com.koushikdutta.async.AsyncServer; import com.koushikdutta.async.callback.CompletedCallback; import com.koushikdutta.async.http.WebSocket; import com.koushikdutta.async.http.server.AsyncHttpServer; import com.koushikdutta.async.http.server.AsyncHttpServerRequest; import com.koushikdutta.async.http.server.AsyncHttpServerResponse; import com.koushikdutta.async.http.server.HttpServerRequestCallback; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.math.BigInteger; import java.net.Inet4Address; import java.net.InetAddress; import java.net.NetworkInterface; import java.net.SocketException; import java.security.SecureRandom; import java.util.ArrayList; import java.util.Collection; import java.util.Enumeration; import java.util.concurrent.CopyOnWriteArrayList; import java.util.concurrent.Executors; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.ScheduledFuture; import java.util.concurrent.TimeUnit; import de.greenrobot.event.EventBus; abstract public class WebServerService extends Service { abstract protected void buildForegroundNotification(NotificationCompat.Builder b); abstract protected boolean configureRoutes(AsyncHttpServer server); abstract protected int getPort(); abstract protected int getMaxIdleTimeSeconds(); abstract protected int getMaxSequentialInvalidRequests(); private static final int NOTIFY_ID = 42408; private AsyncHttpServer server; private SecureRandom rng = new SecureRandom(); private String rootPath; private ScheduledExecutorService timer = Executors.newSingleThreadScheduledExecutor(); private ScheduledFuture<?> timeoutFuture; private int invalidRequestCount = 0; private CopyOnWriteArrayList<WebSocket> sockets = new CopyOnWriteArrayList<WebSocket>(); private Handlebars handlebars; @Override public void onCreate() { super.onCreate(); ConnectivityManager mgr = (ConnectivityManager) getSystemService(CONNECTIVITY_SERVICE); NetworkInfo ni = mgr.getActiveNetworkInfo(); if (ni == null || ni.getType() == ConnectivityManager.TYPE_MOBILE) { EventBus.getDefault().post(new ServerStartRejectedEvent()); stopSelf(); } else { handlebars = new Handlebars(new AssetTemplateLoader(getAssets())); rootPath = "/" + new BigInteger(20, rng).toString(24).toUpperCase(); server = new AsyncHttpServer(); if (configureRoutes(server)) { server.get("/.*", new AssetRequestCallback()); } server.listen(getPort()); raiseReadyEvent(); foregroundify(); timeoutFuture = timer.schedule(onTimeout, getMaxIdleTimeSeconds(), TimeUnit.SECONDS); } } @Override public int onStartCommand(Intent i, int flags, int startId) { return (START_NOT_STICKY); } @Override public void onDestroy() { EventBus.getDefault().removeAllStickyEvents(); EventBus.getDefault().postSticky(new ServerStoppedEvent()); if (server != null) { server.stop(); AsyncServer.getDefault().stop(); // no, really, I mean stop } super.onDestroy(); } @Override public IBinder onBind(Intent intent) { throw new UnsupportedOperationException("Go away"); } protected void serveWebSockets(String relpath, AsyncHttpServer.WebSocketRequestCallback cb) { StringBuilder route = new StringBuilder(rootPath); if (!relpath.startsWith("/")) { route.append('/'); } route.append(relpath); if (cb == null) { cb = new WebSocketClientCallback(); } server.websocket(route.toString(), cb); } private void raiseReadyEvent() { ServerStartedEvent event = new ServerStartedEvent(); try { for (Enumeration<NetworkInterface> enInterfaces = NetworkInterface.getNetworkInterfaces(); enInterfaces .hasMoreElements();) { NetworkInterface ni = enInterfaces.nextElement(); for (Enumeration<InetAddress> enAddresses = ni.getInetAddresses(); enAddresses.hasMoreElements();) { InetAddress addr = enAddresses.nextElement(); if (addr instanceof Inet4Address) { event.addUrl("http://" + addr.getHostAddress() + ":4999" + rootPath + "/"); } } } } catch (SocketException ex) { ex.printStackTrace(); } EventBus.getDefault().removeAllStickyEvents(); EventBus.getDefault().postSticky(event); } private void foregroundify() { NotificationCompat.Builder b = new NotificationCompat.Builder(this); Intent iReceiver = new Intent(this, StopReceiver.class); PendingIntent piReceiver = PendingIntent.getBroadcast(this, 0, iReceiver, 0); b.setAutoCancel(true).setDefaults(Notification.DEFAULT_ALL); buildForegroundNotification(b); b.addAction(R.drawable.ic_stop_white_24dp, getString(R.string.notify_stop), piReceiver); startForeground(NOTIFY_ID, b.build()); } protected String getRootPath() { return (rootPath); } protected Collection<WebSocket> getWebSockets() { return (sockets); } protected void resetTimeout() { timeoutFuture.cancel(false); timeoutFuture = timer.schedule(onTimeout, getMaxIdleTimeSeconds(), TimeUnit.SECONDS); } protected void trackInvalidRequests() { invalidRequestCount++; if (invalidRequestCount > getMaxSequentialInvalidRequests()) { stopSelf(); } } protected Context getContextForPath(String relpath) { throw new IllegalStateException("You need to override this if using Handlebars!"); } private Runnable onTimeout = new Runnable() { @Override public void run() { stopSelf(); } }; private class AssetRequestCallback implements HttpServerRequestCallback { private final AssetManager assets; AssetRequestCallback() { assets = getAssets(); } @Override public void onRequest(AsyncHttpServerRequest request, AsyncHttpServerResponse response) { String path = request.getPath(); try { if (path.startsWith(rootPath)) { path = path.substring(rootPath.length() + 1); } else { handle404(response, path, null); return; } if (path.length() == 0 || "/".equals(path)) { path = "index.html"; } else if (path.startsWith("/")) { path = path.substring(1); } if (path.endsWith(".hbs")) { Template t = handlebars.compile(path); Context ctxt = getContextForPath(path); response.send(t.apply(ctxt)); response.setContentType("text/html"); ctxt.destroy(); } else { AssetFileDescriptor afd = assets.openFd(path); response.sendStream(afd.createInputStream(), afd.getLength()); } resetTimeout(); invalidRequestCount = 0; } catch (IOException e) { handle404(response, path, e); } } private void handle404(AsyncHttpServerResponse response, String path, Exception e) { Log.e(getClass().getSimpleName(), "Invalid URL: " + path, e); response.code(404); response.end(); trackInvalidRequests(); } } private class WebSocketClientCallback implements AsyncHttpServer.WebSocketRequestCallback { @Override public void onConnected(final WebSocket ws, AsyncHttpServerRequest request) { sockets.add(ws); ws.setClosedCallback(new CompletedCallback() { @Override public void onCompleted(Exception ex) { if (ex != null) { Log.e(getClass().getSimpleName(), "Exception with WebSocket", ex); } sockets.remove(ws); } }); } } private static class AssetTemplateLoader extends AbstractTemplateLoader { private final AssetManager mgr; AssetTemplateLoader(AssetManager mgr) { this.mgr = mgr; } @Override public TemplateSource sourceAt(String s) throws IOException { return (new StringTemplateSource(s, slurp(mgr.open(s)))); } } // inspired by http://stackoverflow.com/a/309718/115145 public static String slurp(final InputStream is) throws IOException { final char[] buffer = new char[1024]; final StringBuilder out = new StringBuilder(); final InputStreamReader in = new InputStreamReader(is, "UTF-8"); while (true) { int rsz = in.read(buffer, 0, buffer.length); if (rsz < 0) break; out.append(buffer, 0, rsz); } return (out.toString()); } public static class ServerStartedEvent { private ArrayList<String> urls = new ArrayList<String>(); void addUrl(String url) { urls.add(url); } public ArrayList<String> getUrls() { return (urls); } } public static class ServerStoppedEvent { } public static class ServerStartRejectedEvent { } }