/*
 * 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 io.netty.handler.codec.serialization;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufInputStream;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;

import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.StreamCorruptedException;

A decoder which deserializes the received ByteBufs into Java objects. 
 Please note that the serialized form this decoder expects is not compatible with the standard ObjectOutputStream. Please use ObjectEncoder or ObjectEncoderOutputStream to ensure the interoperability with this decoder. /**
 * A decoder which deserializes the received {@link ByteBuf}s into Java
 * objects.
 * <p>
 * Please note that the serialized form this decoder expects is not
 * compatible with the standard {@link ObjectOutputStream}.  Please use
 * {@link ObjectEncoder} or {@link ObjectEncoderOutputStream} to ensure the
 * interoperability with this decoder.
 */
public class ObjectDecoder extends LengthFieldBasedFrameDecoder {

    private final ClassResolver classResolver;

    
Creates a new decoder whose maximum object size is 1048576 bytes. If the size of the received object is greater than 1048576 bytes, a StreamCorruptedException will be raised. 
Params:
classResolver –  the ClassResolver to use for this decoder/**
     * 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.
     *
     * @param classResolver  the {@link ClassResolver} to use for this decoder
     */
    public ObjectDecoder(ClassResolver classResolver) {
        this(1048576, classResolver);
    }

    
Creates a new decoder with the specified maximum object size.
Params:
maxObjectSize –  the maximum byte length of the serialized object. if the length of the received object is greater than this value, StreamCorruptedException will be raised.
classResolver –  the ClassResolver which will load the class of the serialized object/**
     * 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 StreamCorruptedException}
     *                       will be raised.
     * @param classResolver    the {@link ClassResolver} which will load the class
     *                       of the serialized object
     */
    public ObjectDecoder(int maxObjectSize, ClassResolver classResolver) {
        super(maxObjectSize, 0, 4, 0, 4);
        this.classResolver = classResolver;
    }

    @Override
    protected Object decode(ChannelHandlerContext ctx, ByteBuf in) throws Exception {
        ByteBuf frame = (ByteBuf) super.decode(ctx, in);
        if (frame == null) {
            return null;
        }

        ObjectInputStream ois = new CompactObjectInputStream(new ByteBufInputStream(frame, true), classResolver);
        try {
            return ois.readObject();
        } finally {
            ois.close();
        }
    }
}