96 lines
3.7 KiB
Java
96 lines
3.7 KiB
Java
/*
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* Copyright 2012 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.channel;
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import io.netty.bootstrap.Bootstrap;
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import io.netty.bootstrap.ServerBootstrap;
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import io.netty.channel.ChannelHandler.Sharable;
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import io.netty.util.internal.logging.InternalLogger;
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import io.netty.util.internal.logging.InternalLoggerFactory;
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/**
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* A special {@link ChannelHandler} which offers an easy way to initialize a {@link Channel} once it was
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* registered to its {@link EventLoop}.
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*
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* Implementations are most often used in the context of {@link Bootstrap#handler(ChannelHandler)} ,
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* {@link ServerBootstrap#handler(ChannelHandler)} and {@link ServerBootstrap#childHandler(ChannelHandler)} to
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* setup the {@link ChannelPipeline} of a {@link Channel}.
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*
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* <pre>
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*
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* public class MyChannelInitializer extends {@link ChannelInitializer} {
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* public void initChannel({@link Channel} channel) {
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* channel.pipeline().addLast("myHandler", new MyHandler());
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* }
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* }
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*
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* {@link ServerBootstrap} bootstrap = ...;
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* ...
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* bootstrap.childHandler(new MyChannelInitializer());
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* ...
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* </pre>
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* Be aware that this class is marked as {@link Sharable} and so the implementation must be safe to be re-used.
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*
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* @param <C> A sub-type of {@link Channel}
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*/
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@Sharable
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public abstract class ChannelInitializer<C extends Channel> implements ChannelHandler {
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private static final InternalLogger logger = InternalLoggerFactory.getInstance(ChannelInitializer.class);
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/**
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* This method will be called once the {@link Channel} was registered. After the method returns this instance
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* will be removed from the {@link ChannelPipeline} of the {@link Channel}.
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*
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* @param ch the {@link Channel} which was registered.
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* @throws Exception is thrown if an error occurs. In that case it will be handled by
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* {@link #exceptionCaught(ChannelHandlerContext, Throwable)} which will by default close
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* the {@link Channel}.
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*/
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protected abstract void initChannel(C ch) throws Exception;
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/**
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* Handle the {@link Throwable} by logging and closing the {@link Channel}. Sub-classes may override this.
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*/
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@Override
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public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
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if (logger.isWarnEnabled()) {
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logger.warn("Failed to initialize a channel. Closing: " + ctx.channel(), cause);
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}
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ctx.close();
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}
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/**
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* {@inheritDoc} If override this method ensure you call super!
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*/
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@SuppressWarnings("unchecked")
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@Override
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public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
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try {
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initChannel((C) ctx.channel());
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} catch (Throwable cause) {
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// Explicitly call exceptionCaught(...) as we removed the handler before calling initChannel(...).
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// We do so to prevent multiple calls to initChannel(...).
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exceptionCaught(ctx, cause);
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} finally {
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ChannelPipeline pipeline = ctx.pipeline();
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if (pipeline.context(this) != null) {
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pipeline.remove(this);
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}
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}
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}
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}
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