Allow using third-party HTTP/... stacks for per-network URLs.

Also switch to double-checked locking for
mNetworkBoundSocketFactory and OkHttpClient.

Change-Id: Ic52776ee760036ad5623b7496156b8909dc282fa

core/java/android/net/Network.java

@@ -16,6 +16,7 @@
 
 package android.net;
 
+import android.net.NetworkBoundURLFactory;
 import android.net.NetworkUtils;
 import android.os.Parcelable;
 import android.os.Parcel;
@@ -29,6 +30,8 @@ import java.net.SocketAddress;
 import java.net.SocketException;
 import java.net.UnknownHostException;
 import java.net.URL;
+import java.net.URLStreamHandler;
+import java.util.concurrent.atomic.AtomicReference;
 import javax.net.SocketFactory;
 
 import com.android.okhttp.HostResolver;
@@ -52,8 +55,8 @@ public class Network implements Parcelable {
 
     // Objects used to perform per-network operations such as getSocketFactory
     // and getBoundURL, and a lock to protect access to them.
-    private NetworkBoundSocketFactory mNetworkBoundSocketFactory = null;
-    private OkHttpClient mOkHttpClient = null;
+    private volatile NetworkBoundSocketFactory mNetworkBoundSocketFactory = null;
+    private volatile OkHttpClient mOkHttpClient = null;
     private Object mLock = new Object();
 
     /**
@@ -174,36 +177,83 @@ public class Network implements Parcelable {
      *         {@code Network}.
      */
     public SocketFactory getSocketFactory() {
+        if (mNetworkBoundSocketFactory == null) {
             synchronized (mLock) {
                 if (mNetworkBoundSocketFactory == null) {
                     mNetworkBoundSocketFactory = new NetworkBoundSocketFactory(netId);
                 }
             }
+        }
         return mNetworkBoundSocketFactory;
     }
 
+    /** The default NetworkBoundURLFactory, used if setNetworkBoundURLFactory is never called. */
+    private static final NetworkBoundURLFactory DEFAULT_URL_FACTORY = new NetworkBoundURLFactory() {
+        public URL getBoundURL(final Network network, URL url) throws MalformedURLException {
+            if (network.mOkHttpClient == null) {
+                synchronized (network.mLock) {
+                    if (network.mOkHttpClient == null) {
+                        HostResolver hostResolver = new HostResolver() {
+                            @Override
+                            public InetAddress[] getAllByName(String host)
+                                    throws UnknownHostException {
+                                return network.getAllByName(host);
+                            }
+                        };
+                        network.mOkHttpClient = new OkHttpClient()
+                                .setSocketFactory(network.getSocketFactory())
+                                .setHostResolver(hostResolver);
+                    }
+                }
+            }
+
+            String protocol = url.getProtocol();
+            URLStreamHandler handler = network.mOkHttpClient.createURLStreamHandler(protocol);
+            if (handler == null) {
+                // OkHttpClient only supports HTTP and HTTPS and returns a null URLStreamHandler if
+                // passed another protocol.
+                throw new MalformedURLException("Invalid URL or unrecognized protocol " + protocol);
+            }
+            return new URL(url, "", handler);
+        }
+    };
+
+    private static AtomicReference<NetworkBoundURLFactory> sNetworkBoundURLFactory =
+            new AtomicReference <NetworkBoundURLFactory>(DEFAULT_URL_FACTORY);
+
     /**
-     * Returns a {@link URL} based on the given URL but bound to this {@code Network}.
-     * Note that if this {@code Network} ever disconnects, this factory and any URL object it
-     * produced in the past or future will cease to work.
+     * Returns a {@link URL} based on the given URL but bound to this {@code Network},
+     * such that opening the URL will send all network traffic on this Network.
+     *
+     * Note that if this {@code Network} ever disconnects, any URL object generated by this method
+     * in the past or future will cease to work.
+     *
+     * The returned URL may have a {@link URLStreamHandler} explicitly set, which may not be the
+     * handler generated by the factory set with {@link java.net.URL.setURLStreamHandlerFactory}. To
+     * affect the {@code URLStreamHandler}s of URLs returned by this method, call
+     * {@link #setNetworkBoundURLFactory}.
+     *
+     * Because the returned URLs may have an explicit {@code URLStreamHandler} set, using them as a
+     * context when constructing other URLs and explicitly specifying a {@code URLStreamHandler} may
+     * result in URLs that are no longer bound to the same {@code Network}.
+     *
+     * The default implementation only supports {@code HTTP} and {@code HTTPS} URLs.
      *
      * @return a {@link URL} bound to this {@code Network}.
      */
     public URL getBoundURL(URL url) throws MalformedURLException {
-        synchronized (mLock) {
-            if (mOkHttpClient == null) {
-                HostResolver hostResolver = new HostResolver() {
-                    @Override
-                    public InetAddress[] getAllByName(String host) throws UnknownHostException {
-                        return Network.this.getAllByName(host);
+        return sNetworkBoundURLFactory.get().getBoundURL(this, url);
     }
-                };
-                mOkHttpClient = new OkHttpClient()
-                        .setSocketFactory(getSocketFactory())
-                        .setHostResolver(hostResolver);
+
+    /**
+     * Sets the {@link NetworkBoundURLFactory} to be used by future {@link #getBoundURL} calls.
+     * If {@code null}, clears any factory that was previously specified.
+     */
+    public static void setNetworkBoundURLFactory(NetworkBoundURLFactory factory) {
+        if (factory == null) {
+            factory = DEFAULT_URL_FACTORY;
         }
-        }
-        return new URL(url, "", mOkHttpClient.createURLStreamHandler(url.getProtocol()));
+        sNetworkBoundURLFactory.set(factory);
     }
 
     // implement the Parcelable interface