MessageToMessageEncoder.java — netty Source File

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:
 *
 *   https://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;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelOutboundHandler;
import io.netty.channel.ChannelOutboundHandlerAdapter;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.ChannelPromise;
import io.netty.util.ReferenceCountUtil;
import io.netty.util.ReferenceCounted;
import io.netty.util.concurrent.PromiseCombiner;
import io.netty.util.internal.PlatformDependent;
import io.netty.util.internal.StringUtil;
import io.netty.util.internal.TypeParameterMatcher;

import java.util.List;

/**
 * {@link ChannelOutboundHandlerAdapter} which encodes from one message to an other message
 *
 * For example here is an implementation which decodes an {@link Integer} to an {@link String}.
 *
 * <pre>
 *     public class IntegerToStringEncoder extends
 *             {@link MessageToMessageEncoder}&lt;{@link Integer}&gt; {
 *
 *         {@code @Override}
 *         public void encode({@link ChannelHandlerContext} ctx, {@link Integer} message, List&lt;Object&gt; out)
 *                 throws {@link Exception} {
 *             out.add(message.toString());
 *         }
 *     }
 * </pre>
 *
 * Be aware that you need to call {@link ReferenceCounted#retain()} on messages that are just passed through if they
 * are of type {@link ReferenceCounted}. This is needed as the {@link MessageToMessageEncoder} will call
 * {@link ReferenceCounted#release()} on encoded messages.
 */
public abstract class MessageToMessageEncoder<I> extends ChannelOutboundHandlerAdapter {

    private final TypeParameterMatcher matcher;

    /**
     * Create a new instance which will try to detect the types to match out of the type parameter of the class.
     */
    protected MessageToMessageEncoder() {
// ... (97 more lines)