[Cronet] Initial implementation of HttpURLConnection

components/cronet/android/java/src/org/chromium/net/urlconnection/CronetHttpURLConnection.java

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.net.urlconnection;
+
+import org.chromium.net.ExtendedResponseInfo;
+import org.chromium.net.ResponseInfo;
+import org.chromium.net.UrlRequest;
+import org.chromium.net.UrlRequestContext;
+import org.chromium.net.UrlRequestException;
+import org.chromium.net.UrlRequestListener;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.HttpURLConnection;
+import java.net.URL;
+import java.nio.ByteBuffer;
+import java.util.concurrent.Executor;
+import java.util.concurrent.RejectedExecutionException;
+
+/**
+ * An implementation of HttpURLConnection that uses Cronet to send requests and
+ * receive response. This class inherits a {@code connected} field from the
+ * superclass. That field indicates whether a connection has ever been
+ * attempted.
+ */
+public class CronetHttpURLConnection extends HttpURLConnection {
+    private final UrlRequestContext mUrlRequestContext;
+    private final MessageLoop mMessageLoop;
+    private final UrlRequest mRequest;
+
+    private CronetInputStream mInputStream;
+    private ResponseInfo mResponseInfo;
+    private ByteBuffer mResponseByteBuffer;
+
+    protected CronetHttpURLConnection(URL url,
+            UrlRequestContext urlRequestContext) {
+        super(url);
+        mUrlRequestContext = urlRequestContext;
+        mMessageLoop = new MessageLoop();
+        mRequest = mUrlRequestContext.createRequest(url.toString(),
+                new CronetUrlRequestListener(), new MessageLoopExecutor());
+        mInputStream = new CronetInputStream(this);
+    }
+
+    /**
+     * Wrapper executor class which posts tasks to message loop.
+     */
+    private class MessageLoopExecutor implements Executor {
+        public MessageLoopExecutor() {
+        }
+
+        @Override
+        public void execute(Runnable command)
+                throws RejectedExecutionException {
+            try {
+                mMessageLoop.postTask(command);

[mef, 2014/12/01 18:28:54]

I feel that referencing mMessageLoop from the parent class is a little
confusing. Would it make sense to make MessageLoopExecutor static and pass
MessageLoop to the executor in constructor?

[xunjieli, 2014/12/01 19:19:52]

Done.

+            } catch (InterruptedException e) {
+                throw new RejectedExecutionException(e);
+            }
+        }
+    }
+
+    /**
+     * Opens a connection to the resource. If the connect method is called when
+     * the connection has already been opened (indicated by the connected field
+     * having the value true), the call is ignored.
+     */
+    @Override
+    public void connect() throws IOException {
+        if (connected) {
+            return;
+        }
+        connected = true;
+        mRequest.start();
+        // Blocks until onResponseStarted or onFailed is called.
+        startMessageLoop();
+    }
+
+    /**
+     * Releases this connection so that its resources may be either reused or
+     * closed.
+     */
+    @Override
+    public void disconnect() {
+        // Disconnect before connection is made should have no effect.
+        if (connected) {
+            try {
+                mInputStream.close();
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+            mInputStream = null;
+            mRequest.cancel();
+        }
+    }
+
+    /**
+     * Returns the response message returned by the remote HTTP server.
+     */
+    @Override
+    public String getResponseMessage() throws IOException {
+        connect();
+        if (mResponseInfo == null) {
+            return "";
+        }
+        return mResponseInfo.getHttpStatusText();
+    }
+
+    /**
+     * Returns the response code returned by the remote HTTP server.
+     */
+    @Override
+    public int getResponseCode() throws IOException {
+        connect();
+        if (mResponseInfo == null) {
+            return 0;
+        }
+        return mResponseInfo.getHttpStatusCode();
+    }
+
+    /**
+     * Returns an InputStream for reading data from the resource pointed by this
+     * URLConnection.
+     */
+    @Override
+    public InputStream getInputStream() throws IOException {
+        connect();
+        return mInputStream;
+    }
+
+    /**
+     * Adds the given property to the request header.
+     */
+    @Override
+    public final void addRequestProperty(String key, String value) {
+        // Note that Cronet right now does not allow setting multiple headers
+        // of the same key, see crbug.com/432719 for more details.
+        setRequestProperty(key, value);
+    }
+
+    /**
+     * Sets the value of the specified request header field.
+     */
+    @Override
+    public final void setRequestProperty(String key, String value) {
+        if (connected) {
+            throw new IllegalStateException(
+                    "Cannot set request property after connection is made");
+        }
+        mRequest.addHeader(key, value);
+    }
+
+    /**
+     * Returns whether this connection uses a proxy server.
+     */
+    @Override
+    public boolean usingProxy() {
+        // TODO(xunjieli): implement this.
+        return false;
+    }
+
+    /**
+     * Used by {@link CronetInputStream} to get more data from the network
+     * stack. This should only be called after the request has started. Note
+     * that this call might block if there isn't any more data to be read.
+     */
+    ByteBuffer getMoreData() throws IOException {
+        mResponseByteBuffer = null;
+        startMessageLoop();
+        return mResponseByteBuffer;
+    }
+
+    private class CronetUrlRequestListener implements UrlRequestListener {
+        public CronetUrlRequestListener() {
+        }
+
+        @Override
+        public void onResponseStarted(UrlRequest request, ResponseInfo info) {
+            mResponseInfo = info;
+            // Quits the message loop since we have the headers now.
+            quitMessageLoop();
+        }
+
+        @Override
+        public void onDataReceived(UrlRequest request, ResponseInfo info,
+                ByteBuffer byteBuffer) {
+            mResponseInfo = info;
+            mResponseByteBuffer = ByteBuffer.allocate(byteBuffer.capacity());
+            mResponseByteBuffer.put(byteBuffer);
+            mResponseByteBuffer.flip();
+            quitMessageLoop();
+        }
+
+        @Override
+        public void onRedirect(UrlRequest request, ResponseInfo info,
+                String newLocationUrl) {
+            // TODO(xunjieli): Handle redirect and test it.
+        }
+
+        @Override
+        public void onSucceeded(UrlRequest request, ExtendedResponseInfo info) {
+            mResponseInfo = info.getResponseInfo();
+            setResponseDataCompleted();
+        }
+
+        @Override
+        public void onFailed(UrlRequest request, ResponseInfo info,
+                UrlRequestException exception) {
+            // TODO(xunjieli): Handle failure.
+            setResponseDataCompleted();
+        }
+
+        /**
+         * Notifies {@link #mInputStream} that transferring of response data has
+         * completed.
+         */
+        private void setResponseDataCompleted() {
+            if (mInputStream != null) {
+                mInputStream.setResponseDataCompleted();
+            }
+            quitMessageLoop();
+        }
+    }
+
+    /**
+     * Posts a quit task to the message loop.
+     */
+    private void quitMessageLoop() {
+        try {
+            mMessageLoop.postQuitTask();
+        } catch (InterruptedException e) {
+            // ignored.
+        }
+    }
+
+    /**
+     * Starts running the message Loop.
+     */
+    private void startMessageLoop() throws IOException {

[mef, 2014/12/01 18:28:54]

Doesn't it block until loop is done? 
Would it make sense to name it 'runMessageLoop()'?

[xunjieli, 2014/12/01 19:19:52]

Done.

+        try {
+            mMessageLoop.loop();

[mef, 2014/12/01 18:28:54]

Should we rethrow all exceptions thrown from the loop as IOException?
Also, what happens if let's say getResponseCode throws an exception, and
embedder calls getResponseMessage after that?

[xunjieli, 2014/12/01 19:19:52]

Done. I guess the caller will need to handle IOException by either rethrowing or
using try-catch block. If both getResponseCode() and getResponseMessage() are in
one try-catch block, then the second one won't be invoked since there will be an
exception. If these two methods are in two different try-catch, then
getResponseMessage() will be run.

+        } catch (InterruptedException e) {
+            throw new IOException(e);
+        }
+    }
+}