[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 android.os.Handler;
+import android.os.Looper;
+
+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;
+
+/**
+ * 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 UrlRequest mRequest;
+
+    private ResponseInfo mResponseInfo;
+
+    private InputStream mResponseBody;
+
+    protected CronetHttpURLConnection(URL url,
+            UrlRequestContext urlRequestContext) {
+        super(url);
+        mUrlRequestContext = urlRequestContext;
+    }
+
+    /**
+     * Wrapper executor class which posts tasks to current looper.
+     */
+    private static class HandlerThreadExecutor implements Executor {

[mef, 2014/11/13 19:16:17]

Maybe we should consider passing Looper to Async API.

+        private final Handler mHandler;
+
+        public HandlerThreadExecutor() {
+            if (Looper.myLooper() == null) {
+                Looper.prepare();
+            }
+            mHandler = new Handler(Looper.myLooper());
+        }
+
+        @Override
+        public void execute(Runnable command) {
+            mHandler.post(command);
+        }
+    }
+
+    /**
+     * Opens a connection to the resource.
+     */
+    @Override
+    public void connect() throws IOException {
+        maybeStartRequest();
+    }
+
+    /**
+     * Releases this connection so that its resources may be either reused or
+     * closed.
+     */
+    @Override
+    public void disconnect() {
+        if (mResponseBody != null) {
+            try {
+                mResponseBody.close();
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+        }
+    }
+
+    /**
+     * Returns the response message returned by the remote HTTP server.
+     */
+    @Override
+    public String getResponseMessage() {
+        maybeStartRequest();
+        return mResponseInfo.getHttpStatusText();
+    }
+
+    /**
+     * Returns the response code returned by the remote HTTP server.
+     */
+    @Override
+    public int getResponseCode() {
+        maybeStartRequest();
+        return mResponseInfo.getHttpStatusCode();
+    }
+
+    /**
+     * Returns an InputStream for reading data from the resource pointed by this
+     * URLConnection.
+     */
+    @Override
+    public InputStream getInputStream() {
+        maybeStartRequest();
+        return mResponseBody;
+    }
+
+    /**
+     * Adds the given property to the request header.
+     */
+    @Override
+    public final void addRequestProperty(String key, String value) {

[mef, 2014/11/13 19:16:17]

I guess 'add' should allow multiple headers with the same name and 'set'
shouldn't?

[xunjieli, 2014/11/13 19:24:11]

Yes, that's the desired behavior. But due to a limitation in Cronet's Async API
(https://code.google.com/p/chromium/issues/detail?id=432719), no matter what we
do on the HttpURLConnection side, only one distinct header-value entry will be
sent. We will need to fix this after we figured out what to do with Cronet's
async APIs (https://code.google.com/p/chromium/issues/detail?id=432719).

+        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");
+        }
+        maybeCreateRequest();
+        mRequest.addHeader(key, value);
+    }
+
+    /**
+     * Returns whether this connection uses a proxy server or not.
+     */
+    @Override
+    public boolean usingProxy() {
+        // TODO(xunjieli): implement this.
+        return false;
+    }
+
+    private class CronetUrlRequestListener implements UrlRequestListener {
+
+        public CronetUrlRequestListener() {
+        }
+
+        @Override
+        public void onResponseStarted(UrlRequest request, ResponseInfo info) {
+            mResponseInfo = info;
+        }
+
+        @Override
+        public void onDataReceived(UrlRequest request, ResponseInfo info,
+                ByteBuffer byteBuffer) {
+            mResponseInfo = info;
+            // TODO(xunjieli): handle streaming.
+            mResponseBody = new ByteBufferInputStream(byteBuffer);

[mef, 2014/11/13 19:16:17]

Yeah, this is wrong. You need to copy data from |byteBuffer| elsewhere.

[xunjieli, 2014/11/13 19:24:11]

Acknowledged. Will do.

+        }
+
+        @Override
+        public void onRedirect(UrlRequest request, ResponseInfo info,
+                String newLocationUrl) {
+            // TODO(xunjieli): handle redirect.
+            mResponseInfo = info;
+        }
+
+        @Override
+        public void onSucceeded(UrlRequest request, ExtendedResponseInfo info) {
+            Looper.myLooper().quit();
+        }
+
+        @Override
+        public void onFailed(UrlRequest request, ResponseInfo info,
+                UrlRequestException exception) {
+            // TODO(xunjieli): handle failure.
+            Looper.myLooper().quit();
+        }
+    }
+
+    /**
+     * Maybe starts {@code mRequest}, and waits for it to complete.
+     */
+    private void maybeStartRequest() {
+        if (connected) {
+            return;
+        }
+        maybeCreateRequest();
+        mRequest.start();
+        connected = true;
+        Looper.loop();

[mmenke, 2014/11/13 19:31:27]

Problem:  This is noticeable to the embedder, and can cause tasks to run that
they may not expect to do so.  Unless the standard HttpURLConnection spins the
current Looper, we shouldn't be doing this.

For example, suppose one of those tasks starts another HttpURLConnection....

I seem to recall Java or Android has a standard message loop/queue class of some
sort that we could just spin up and run until done (Basically like looper, but
private, so we only run tasks we post to it ourselves).

+    }
+
+    /**
+     * Maybe creates {@code mRequest} if it is null.
+     */
+    private void maybeCreateRequest() {
+        if (mRequest != null) {
+            return;
+        }
+        mRequest = mUrlRequestContext.createRequest(url.toString(),
+                new CronetUrlRequestListener(), new HandlerThreadExecutor());
+    }
+}