[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.BlockingQueue;
+import java.util.concurrent.Executor;
+import java.util.concurrent.LinkedBlockingQueue;
+
+/**
+ * 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 BlockingQueue<MessageLoop.Message> mMessageQueue;
+
+    private final UrlRequest mRequest;

[mmenke, 2014/11/21 16:53:07]

optional:  Maybe another line break here, to emphasize the value above this is
final, unlike the information about the response.

[xunjieli, 2014/11/21 20:30:55]

Done.

+    private ResponseInfo mResponseInfo;
+    private CronetInputStream mInputStream;
+    private ByteBuffer mResponseByteBuffer;
+
+    protected CronetHttpURLConnection(URL url,
+            UrlRequestContext urlRequestContext) {
+        super(url);
+        mUrlRequestContext = urlRequestContext;
+        mMessageQueue = new LinkedBlockingQueue<MessageLoop.Message>();
+        mMessageLoop = new MessageLoop(mMessageQueue);
+        mRequest = mUrlRequestContext.createRequest(url.toString(),
+                new CronetUrlRequestListener(), new HandlerThreadExecutor());
+    }
+
+    /**
+     * Wrapper executor class which posts tasks to current looper.
+     */
+    private class HandlerThreadExecutor implements Executor {
+        public HandlerThreadExecutor() {
+        }
+
+        @Override
+        public void execute(Runnable command) {
+            try {
+                mMessageQueue.put(new MessageLoop.Message(command));
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+        }
+    }
+
+    /**
+     * 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 {
+        maybeStartRequest();
+    }
+
+    /**
+     * Releases this connection so that its resources may be either reused or
+     * closed.
+     */
+    @Override
+    public void disconnect() {
+        if (mInputStream != null) {
+            try {
+                mInputStream.close();

[mmenke, 2014/11/21 16:53:07]

mInputStream = null, so we handle multiple calls?  Also, what if this is called
before connect(), should we not do anything in connect, or throw an exception or
something?  What does the default implementation do?

[xunjieli, 2014/11/21 20:30:55]

OkHttp does nothing if it is called multiple times or it is called before
connect(). See
http://androidxref.com/4.4.3_r1.1/xref/external/okhttp/src/main/java/com/squa....
I am not sure if I should do mRequest.cancel() here, it seems that I should not
do that.

[mmenke, 2014/11/21 21:26:12]

Hrm...ok, so looks like we're copying their behavior, weird though it is.

+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+        }
+    }
+
+    /**
+     * Returns the response message returned by the remote HTTP server.
+     */
+    @Override
+    public String getResponseMessage() {

[mmenke, 2014/11/21 16:53:07]

We don't have any tests exercise this.

[xunjieli, 2014/11/21 20:30:55]

Done.

+        maybeStartRequest();

[mmenke, 2014/11/21 16:53:07]

It's a pain, but we should probably test all these implicit start calls.

[xunjieli, 2014/11/21 20:30:56]

Acknowledged. Will keep this in mind and handle it after fixing other test
issues.

+        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() {
+        if (mInputStream == null) {
+            maybeStartRequest();
+            mInputStream = new CronetInputStream(this);
+        }
+        return mInputStream;
+    }
+
+    /**
+     * Adds the given property to the request header.
+     */
+    @Override
+    public final void addRequestProperty(String key, String value) {
+        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 or not.
+     */
+    @Override
+    public boolean usingProxy() {
+        // TODO(xunjieli): implement this.
+        return false;
+    }
+
+    /**
+     * Used by {@link CronetInputStream} to request more data from the network
+     * stack. Note that this call might block if there isn't any more data to be
+     * read.

[mmenke, 2014/11/21 16:53:07]

Worth noting that this may only be called after the request has started.

[xunjieli, 2014/11/21 20:30:56]

Done.

+     */
+    ByteBuffer requestData() {

[mmenke, 2014/11/21 16:53:06]

maybe requestMoreData?  ("Request data" could be a noun, with request as an
adjective, or a verb phrase, with request as a verb.  The "more" removes that
ambiguity).

Or maybe just getMoreData, since we aren't actually sending the request here.

[xunjieli, 2014/11/21 20:30:56]

Done.

+        mMessageLoop.loop();
+        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.
+            mMessageLoop.quit();
+        }
+
+        @Override
+        public void onDataReceived(UrlRequest request, ResponseInfo info,
+                ByteBuffer byteBuffer) {
+            mResponseInfo = info;
+            mResponseByteBuffer = ByteBuffer.allocate(byteBuffer.capacity());
+            mResponseByteBuffer.put(byteBuffer);
+            mResponseByteBuffer.rewind();
+            mMessageLoop.quit();
+        }
+
+        @Override
+        public void onRedirect(UrlRequest request, ResponseInfo info,
+                String newLocationUrl) {
+            // TODO(xunjieli): Handle redirect.
+            mResponseInfo = info;
+        }
+
+        @Override
+        public void onSucceeded(UrlRequest request, ExtendedResponseInfo info) {
+            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();
+            }
+            mMessageLoop.quit();
+        }
+    }
+
+    /**
+     * On first call, creates and starts UrlRequest, and waits until response
+     * headers are received. Does nothing on subsequent calls.
+     */
+    private void maybeStartRequest() {
+        if (connected) {
+            return;
+        }
+        connected = true;
+        mRequest.start();
+        // Blocks until onResponseStarted or onFailed is called.
+        mMessageLoop.loop();
+    }
+}