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Java example source code file (CompatibleObjectEncoder.java)

This example Java source code file (CompatibleObjectEncoder.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

attributekey, bytebuf, bytebufoutputstream, compatibleobjectencoder, exception, illegalargumentexception, messagetobyteencoder, objectoutputstream, oos, override, reset, serializable

The CompatibleObjectEncoder.java Java example source code

/*
 * 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.ByteBufOutputStream;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;
import io.netty.util.Attribute;
import io.netty.util.AttributeKey;

import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.io.Serializable;

/**
 * An encoder which serializes a Java object into a {@link ByteBuf}
 * (interoperability version).
 * <p>
 * This encoder is interoperable with the standard Java object streams such as
 * {@link ObjectInputStream} and {@link ObjectOutputStream}.
 */
public class CompatibleObjectEncoder extends MessageToByteEncoder<Serializable> {

    private static final AttributeKey<ObjectOutputStream> OOS =
            AttributeKey.valueOf(CompatibleObjectEncoder.class, "OOS");

    private final int resetInterval;
    private int writtenObjects;

    /**
     * Creates a new instance with the reset interval of {@code 16}.
     */
    public CompatibleObjectEncoder() {
        this(16); // Reset at every sixteen writes
    }

    /**
     * Creates a new instance.
     *
     * @param resetInterval
     *        the number of objects between {@link ObjectOutputStream#reset()}.
     *        {@code 0} will disable resetting the stream, but the remote
     *        peer will be at the risk of getting {@link OutOfMemoryError} in
     *        the long term.
     */
    public CompatibleObjectEncoder(int resetInterval) {
        if (resetInterval < 0) {
            throw new IllegalArgumentException(
                    "resetInterval: " + resetInterval);
        }
        this.resetInterval = resetInterval;
    }

    /**
     * Creates a new {@link ObjectOutputStream} which wraps the specified
     * {@link OutputStream}.  Override this method to use a subclass of the
     * {@link ObjectOutputStream}.
     */
    protected ObjectOutputStream newObjectOutputStream(OutputStream out) throws Exception {
        return new ObjectOutputStream(out);
    }

    @Override
    protected void encode(ChannelHandlerContext ctx, Serializable msg, ByteBuf out) throws Exception {
        Attribute<ObjectOutputStream> oosAttr = ctx.attr(OOS);
        ObjectOutputStream oos = oosAttr.get();
        if (oos == null) {
            oos = newObjectOutputStream(new ByteBufOutputStream(out));
            ObjectOutputStream newOos = oosAttr.setIfAbsent(oos);
            if (newOos != null) {
                oos = newOos;
            }
        }

        synchronized (oos) {
            if (resetInterval != 0) {
                // Resetting will prevent OOM on the receiving side.
                writtenObjects ++;
                if (writtenObjects % resetInterval == 0) {
                    oos.reset();
                }
            }

            oos.writeObject(msg);
            oos.flush();
        }
    }
}

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