/*
* Copyright 2012 The Netty Project
*
* The Netty Project licenses this file to you 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.facebook.presto.jdbc.internal.netty.handler.codec.marshalling;
import java.io.StreamCorruptedException;
import org.jboss.marshalling.ByteInput;
import org.jboss.marshalling.Unmarshaller;
import com.facebook.presto.jdbc.internal.netty.buffer.ChannelBuffer;
import com.facebook.presto.jdbc.internal.netty.channel.Channel;
import com.facebook.presto.jdbc.internal.netty.channel.ChannelHandlerContext;
import com.facebook.presto.jdbc.internal.netty.handler.codec.frame.LengthFieldBasedFrameDecoder;
import com.facebook.presto.jdbc.internal.netty.handler.codec.frame.TooLongFrameException;
/**
* Decoder which MUST be used with {@link MarshallingEncoder}.
*
* A {@link LengthFieldBasedFrameDecoder} which use an {@link Unmarshaller} to read the Object out
* of the {@link ChannelBuffer}.
*
*/
public class MarshallingDecoder extends LengthFieldBasedFrameDecoder {
private final UnmarshallerProvider provider;
/**
* Creates a new decoder whose maximum object size is {@code 1048576}
* bytes. If the size of the received object is greater than
* {@code 1048576} bytes, a {@link StreamCorruptedException} will be
* raised.
*
*/
public MarshallingDecoder(UnmarshallerProvider provider) {
this(provider, 1048576);
}
/**
* Creates a new decoder with the specified maximum object size.
*
* @param maxObjectSize the maximum byte length of the serialized object.
* if the length of the received object is greater
* than this value, {@link TooLongFrameException}
* will be raised.
*/
public MarshallingDecoder(UnmarshallerProvider provider, int maxObjectSize) {
super(maxObjectSize, 0, 4, 0, 4);
this.provider = provider;
}
@Override
protected Object decode(
ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer) throws Exception {
ChannelBuffer frame = (ChannelBuffer) super.decode(ctx, channel, buffer);
if (frame == null) {
return null;
}
Unmarshaller unmarshaller = provider.getUnmarshaller(ctx);
ByteInput input = new ChannelBufferByteInput(frame);
try {
unmarshaller.start(input);
Object obj = unmarshaller.readObject();
unmarshaller.finish();
return obj;
} finally {
// Call close in a finally block as the ReplayingDecoder will throw an Error if not
// enough bytes are readable. This helps to be sure that we do not leak resource
unmarshaller.close();
}
}
@Override
protected ChannelBuffer extractFrame(ChannelBuffer buffer, int index, int length) {
return buffer.slice(index, length);
}
}