[Cronet] Change interface APIs to abstract classes

components/cronet/android/java/src/org/chromium/net/UploadDataProvider.java

 // Copyright 2015 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;
 
 import java.io.IOException;
 import java.nio.ByteBuffer;
 
 /**
  * Interface allowing the embedder to provide an upload body to

[xunjieli, 2015/09/03 04:32:02]

nit: s/Interface/Abstract class

[pauljensen, 2015/09/11 15:20:41]

Done.

  * {@link UrlRequest}. It supports both non-chunked (size known in advanced) and
  * chunked (size not known in advance) uploads. Be aware that not all servers
  * support chunked uploads.
  *
  * <p>An upload is either always chunked, across multiple uploads if the data
  * ends up being sent more than once, or never chunked.
  */
-public interface UploadDataProvider {
+public abstract class UploadDataProvider {

[xunjieli, 2015/09/03 04:32:02]

Although the guideline says we should *always* prefer abstract classes over
interfaces, I am not sure if we should change this one. I see why we might want
to change UrlRequestListener to an abstract class. But for UploadDataProvider,
if we do not know the form of underlying data (whether it's an array, buffer,
channel), it will be pretty hard to provide default states/implementations. Do
you have any use case in mind that we might need to augment this?

[pauljensen, 2015/09/11 15:20:41]

I'm just trying to future-proof us.  I could image wacky and weird things being
necessary in the future like:
   boolean isIdempotent()
   boolean canGZip()
   boolean isHangingPost()

     /**
      * If this is a non-chunked upload, returns the length of the upload. Must
      * always return -1 if this is a chunked upload.
      * @return the length of the upload for non-chunked uploads, -1 otherwise.
      */
-    public long getLength();
+    public abstract long getLength();
 
     /**
      * Reads upload data into {@code byteBuffer}. Upon completion, the buffer's
      * position is updated to the end of the bytes that were read. The buffer's
      * limit is not changed. Each call of this method must be followed be a
      * single call, either synchronous or asynchronous, to
      * {@code uploadDataSink}: {@link UploadDataSink#onReadSucceeded} on success
      * or {@link UploadDataSink#onReadError} on failure. Neither read nor rewind
      * will be called until one of those methods or the other is called. Even if
      * the associated {@link UrlRequest} is cancelled, one or the other must
      * still be called before resources can be safely freed. Throwing an
      * exception will also result in resources being freed and the request being
      * errored out.
      *
      * @param uploadDataSink The object to notify when the read has completed,
      *            successfully or otherwise.
      * @param byteBuffer The buffer to copy the read bytes into.
      * @throws IOException if any IOException occurred during the process.
      */
-    public void read(UploadDataSink uploadDataSink, ByteBuffer byteBuffer)
+    public abstract void read(UploadDataSink uploadDataSink, ByteBuffer byteBuffer)
             throws IOException;
 
     /**
      * Rewinds upload data. Each call must be followed be a single
      * call, either synchronous or asynchronous, to {@code uploadDataSink}:
      * {@link UploadDataSink#onRewindSucceeded} on success or
      * {@link UploadDataSink#onRewindError} on failure. Neither read nor rewind
      * will be called until one of those methods or the other is called.
      * Even if the associated {@link UrlRequest} is cancelled, one or the other
      * must still be called before resources can be safely freed. Throwing an
      * exception will also result in resources being freed and the request being
      * errored out.
      *
      * <p>If rewinding is not supported, this should call
      * {@link UploadDataSink#onRewindError}. Note that rewinding is required to
      * follow redirects that preserve the upload body, and for retrying when the
      * server times out stale sockets.
      *
      * @param uploadDataSink The object to notify when the rewind operation has
      *         completed, successfully or otherwise.
      * @throws IOException if any IOException occurred during the process.
      */
-    public void rewind(UploadDataSink uploadDataSink)
-            throws IOException;
+    public abstract void rewind(UploadDataSink uploadDataSink) throws IOException;
 }