googleapis · aozarov · Oct 19, 2015 · Oct 15, 2015 · Oct 16, 2015 · Oct 16, 2015
diff --git a/gcloud-java-core/src/main/java/com/google/gcloud/RestorableState.java b/gcloud-java-core/src/main/java/com/google/gcloud/RestorableState.java
@@ -0,0 +1,32 @@
+/*
+ * Copyright 2015 Google Inc. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.gcloud;
+
+/**
+ * A common interface for restorable states. Implementations of {@code RestorableState} are capable
+ * of saving the state of an object to restore it for later use.
+ *
+ * Implementations of this class must implement {@link java.io.Serializable} to ensure that the
+ * state of a the object can be correctly serialized.
+ */
+public interface RestorableState<T> {
+
+  /**
+   * Returns an object whose internal state reflects the one saved in the invocation object.
+   */
+  T restore();
+}
diff --git a/gcloud-java-storage/src/main/java/com/google/gcloud/storage/BlobReadChannel.java b/gcloud-java-storage/src/main/java/com/google/gcloud/storage/BlobReadChannel.java
@@ -16,9 +16,10 @@
 
 package com.google.gcloud.storage;
 
+import com.google.gcloud.RestorableState;
+
 import java.io.Closeable;
 import java.io.IOException;
-import java.io.Serializable;
 import java.nio.channels.ReadableByteChannel;
 
 /**
@@ -28,7 +29,7 @@
  *
  * This class is @{link Serializable}, which allows incremental reads.
  */
-public interface BlobReadChannel extends ReadableByteChannel, Serializable, Closeable {
+public interface BlobReadChannel extends ReadableByteChannel, Closeable {
 
   /**
    * Overridden to remove IOException.
@@ -46,4 +47,11 @@ public interface BlobReadChannel extends ReadableByteChannel, Serializable, Clos
    */
   void chunkSize(int chunkSize);
 
+  /**
+   * Saves the read channel state.
+   *
+   * @return a {@link RestorableState} object that contains the read channel state and can restore
+   *     it afterwards. State object must implement {@link java.io.Serializable}.
+   */
+  public RestorableState<BlobReadChannel> save();
 }
diff --git a/gcloud-java-storage/src/main/java/com/google/gcloud/storage/BlobReadChannelImpl.java b/gcloud-java-storage/src/main/java/com/google/gcloud/storage/BlobReadChannelImpl.java
@@ -19,14 +19,16 @@
 import static com.google.gcloud.RetryHelper.runWithRetries;
 
 import com.google.api.services.storage.model.StorageObject;
+import com.google.common.base.MoreObjects;
+import com.google.gcloud.RestorableState;
 import com.google.gcloud.RetryHelper;
 import com.google.gcloud.spi.StorageRpc;
 
 import java.io.IOException;
-import java.io.ObjectInputStream;
-import java.io.ObjectOutputStream;
+import java.io.Serializable;
 import java.nio.ByteBuffer;
 import java.util.Map;
+import java.util.Objects;
 import java.util.concurrent.Callable;
 
 /**
@@ -35,7 +37,6 @@
 class BlobReadChannelImpl implements BlobReadChannel {
 
   private static final int DEFAULT_CHUNK_SIZE = 2 * 1024 * 1024;
-  private static final long serialVersionUID = 4821762590742862669L;
 
   private final StorageOptions serviceOptions;
   private final BlobId blob;
@@ -45,38 +46,33 @@ class BlobReadChannelImpl implements BlobReadChannel {
   private boolean endOfStream;
   private int chunkSize = DEFAULT_CHUNK_SIZE;
 
-  private transient StorageRpc storageRpc;
-  private transient StorageObject storageObject;
-  private transient int bufferPos;
-  private transient byte[] buffer;
+  private final StorageRpc storageRpc;
+  private final StorageObject storageObject;
+  private int bufferPos;
+  private byte[] buffer;
 
   BlobReadChannelImpl(StorageOptions serviceOptions, BlobId blob,
       Map<StorageRpc.Option, ?> requestOptions) {
     this.serviceOptions = serviceOptions;
     this.blob = blob;
     this.requestOptions = requestOptions;
     isOpen = true;
-    initTransients();
+    storageRpc = serviceOptions.storageRpc();
+    storageObject = blob.toPb();
   }
 
-  private void writeObject(ObjectOutputStream out) throws IOException {
+  @Override
+  public RestorableState<BlobReadChannel> save() {
+    StateImpl.Builder builder = StateImpl.builder(serviceOptions, blob, requestOptions)
+        .position(position)
+        .isOpen(isOpen)
+        .endOfStream(endOfStream)
+        .chunkSize(chunkSize);
     if (buffer != null) {
-      position += bufferPos;
-      buffer = null;
-      bufferPos = 0;
-      endOfStream = false;
+      builder.position(position + bufferPos);
+      builder.endOfStream(false);
     }
-    out.defaultWriteObject();
-  }
-
-  private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
-    in.defaultReadObject();
-    initTransients();
-  }
-
-  private void initTransients() {
-    storageRpc = serviceOptions.storageRpc();
-    storageObject = blob.toPb();
+    return builder.build();
   }
 
   @Override
@@ -148,4 +144,116 @@ public byte[] call() {
     }
     return toWrite;
   }
+
+  static class StateImpl implements RestorableState<BlobReadChannel>, Serializable {
+
+    private static final long serialVersionUID = 3889420316004453706L;
+
+    private final StorageOptions serviceOptions;
+    private final BlobId blob;
+    private final Map<StorageRpc.Option, ?> requestOptions;
+    private final int position;
+    private final boolean isOpen;
+    private final boolean endOfStream;
+    private final int chunkSize;
+
+    StateImpl(Builder builder) {
+      this.serviceOptions = builder.serviceOptions;
+      this.blob = builder.blob;
+      this.requestOptions = builder.requestOptions;
+      this.position = builder.position;
+      this.isOpen = builder.isOpen;
+      this.endOfStream = builder.endOfStream;
+      this.chunkSize = builder.chunkSize;
+    }
+
+    static class Builder {
+      private final StorageOptions serviceOptions;
+      private final BlobId blob;
+      private final Map<StorageRpc.Option, ?> requestOptions;
+      private int position;
+      private boolean isOpen;
+      private boolean endOfStream;
+      private int chunkSize;
+
+      private Builder(StorageOptions options, BlobId blob, Map<StorageRpc.Option, ?> reqOptions) {
+        this.serviceOptions = options;
+        this.blob = blob;
+        this.requestOptions = reqOptions;
+      }
+
+      Builder position(int position) {
+        this.position = position;
+        return this;
+      }
+
+      Builder isOpen(boolean isOpen) {
+        this.isOpen = isOpen;
+        return this;
+      }
+
+      Builder endOfStream(boolean endOfStream) {
+        this.endOfStream = endOfStream;
+        return this;
+      }
+
+      Builder chunkSize(int chunkSize) {
+        this.chunkSize = chunkSize;
+        return this;
+      }
+
+      RestorableState<BlobReadChannel> build() {
+        return new StateImpl(this);
+      }
+    }
+
+    static Builder builder(
+        StorageOptions options, BlobId blob, Map<StorageRpc.Option, ?> reqOptions) {
+      return new Builder(options, blob, reqOptions);
+    }
+
+    @Override
+    public BlobReadChannel restore() {
+      BlobReadChannelImpl channel = new BlobReadChannelImpl(serviceOptions, blob, requestOptions);
+      channel.position = position;
+      channel.isOpen = isOpen;
+      channel.endOfStream = endOfStream;
+      channel.chunkSize = chunkSize;
+      return channel;
+    }
+
+    @Override
+    public int hashCode() {
+      return Objects.hash(serviceOptions, blob, requestOptions, position, isOpen, endOfStream,
+          chunkSize);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+      if (obj == null) {
+        return false;
+      }
+      if (!(obj instanceof StateImpl)) {
+        return false;
+      }
+      final StateImpl other = (StateImpl) obj;
+      return Objects.equals(this.serviceOptions, other.serviceOptions)
+          && Objects.equals(this.blob, other.blob)
+          && Objects.equals(this.requestOptions, other.requestOptions)
+          && this.position == other.position
+          && this.isOpen == other.isOpen
+          && this.endOfStream == other.endOfStream
+          && this.chunkSize == other.chunkSize;
+    }
+
+    @Override
+    public String toString() {
+      return MoreObjects.toStringHelper(this)
+          .add("blob", blob)
+          .add("position", position)
+          .add("isOpen", isOpen)
+          .add("endOfStream", endOfStream)
+          .toString();
+    }
+  }
 }
diff --git a/gcloud-java-storage/src/main/java/com/google/gcloud/storage/BlobWriteChannel.java b/gcloud-java-storage/src/main/java/com/google/gcloud/storage/BlobWriteChannel.java
@@ -16,8 +16,9 @@
 
 package com.google.gcloud.storage;
 
+import com.google.gcloud.RestorableState;
+
 import java.io.Closeable;
-import java.io.Serializable;
 import java.nio.channels.WritableByteChannel;
 
 /**
@@ -27,11 +28,21 @@
  * data will only be visible after calling {@link #close()}. This class is serializable, to allow
  * incremental writes.
  */
-public interface BlobWriteChannel extends WritableByteChannel, Serializable, Closeable {
+public interface BlobWriteChannel extends WritableByteChannel, Closeable {
 
   /**
    * Sets the minimum size that will be written by a single RPC.
    * Written data will be buffered and only flushed upon reaching this size or closing the channel.
    */
   void chunkSize(int chunkSize);
+
+  /**
+   * Saves the write channel state so that it can be restored afterwards. The original
+   * {@code BlobWriteChannel} and the restored one should not both be used. Closing one channel
+   * causes the other channel to close, subsequent writes will fail.
+   *
+   * @return a {@link RestorableState} object that contains the write channel state and can restore
+   *     it afterwards. State object must implement {@link java.io.Serializable}.
+   */
+  public RestorableState<BlobWriteChannel> save();
 }