/*
* 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.serialization;
import static com.facebook.presto.jdbc.internal.netty.buffer.ChannelBuffers.*;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import com.facebook.presto.jdbc.internal.netty.buffer.ChannelBuffer;
import com.facebook.presto.jdbc.internal.netty.buffer.ChannelBufferOutputStream;
import com.facebook.presto.jdbc.internal.netty.channel.Channel;
import com.facebook.presto.jdbc.internal.netty.channel.ChannelHandler.Sharable;
import com.facebook.presto.jdbc.internal.netty.channel.ChannelHandlerContext;
import com.facebook.presto.jdbc.internal.netty.handler.codec.oneone.OneToOneEncoder;
/**
* An encoder which serializes a Java object into a {@link ChannelBuffer}.
* <p>
* Please note that the serialized form this encoder produces is not
* compatible with the standard {@link ObjectInputStream}. Please use
* {@link ObjectDecoder} or {@link ObjectDecoderInputStream} to ensure the
* interoperability with this encoder.
*
* @apiviz.landmark
* @apiviz.has com.facebook.presto.jdbc.internal.netty.handler.codec.serialization.ObjectEncoderOutputStream - - - compatible with
*/
@Sharable
public class ObjectEncoder extends OneToOneEncoder {
private static final byte[] LENGTH_PLACEHOLDER = new byte[4];
private final int estimatedLength;
/**
* Creates a new encoder with the estimated length of 512 bytes.
*/
public ObjectEncoder() {
this(512);
}
/**
* Creates a new encoder.
*
* @param estimatedLength
* the estimated byte length of the serialized form of an object.
* If the length of the serialized form exceeds this value, the
* internal buffer will be expanded automatically at the cost of
* memory bandwidth. If this value is too big, it will also waste
* memory bandwidth. To avoid unnecessary memory copy or allocation
* cost, please specify the properly estimated value.
*/
public ObjectEncoder(int estimatedLength) {
if (estimatedLength < 0) {
throw new IllegalArgumentException(
"estimatedLength: " + estimatedLength);
}
this.estimatedLength = estimatedLength;
}
@Override
protected Object encode(ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
ChannelBufferOutputStream bout =
new ChannelBufferOutputStream(dynamicBuffer(
estimatedLength, ctx.getChannel().getConfig().getBufferFactory()));
bout.write(LENGTH_PLACEHOLDER);
ObjectOutputStream oout = new CompactObjectOutputStream(bout);
oout.writeObject(msg);
oout.flush();
oout.close();
ChannelBuffer encoded = bout.buffer();
encoded.setInt(0, encoded.writerIndex() - 4);
return encoded;
}
}