68 lines
2.5 KiB
Java
68 lines
2.5 KiB
Java
/*
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* Copyright 2013 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.util.internal.InternalThreadLocalMap;
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import java.lang.reflect.AnnotatedType;
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import java.util.Map;
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/**
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* Skeleton implementation of a {@link ChannelHandler}.
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*/
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public abstract class ChannelHandlerAdapter implements ChannelHandler {
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// Not using volatile because it's used only for a sanity check.
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boolean added;
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/**
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* Throws {@link IllegalStateException} if {@link ChannelHandlerAdapter#isSharable()} returns {@code true}
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*/
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protected void ensureNotSharable() {
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if (isSharable()) {
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throw new IllegalStateException("ChannelHandler " + getClass().getName() + " is not allowed to be shared");
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}
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}
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/**
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* Return {@code true} if the implementation is {@link Sharable} and so can be added
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* to different {@link ChannelPipeline}s.
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*/
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public boolean isSharable() {
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/**
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* Cache the result of {@link Sharable} annotation detection to workaround a condition. We use a
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* {@link ThreadLocal} and {@link WeakHashMap} to eliminate the volatile write/reads. Using different
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* {@link WeakHashMap} instances per {@link Thread} is good enough for us and the number of
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* {@link Thread}s are quite limited anyway.
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*
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* See <a href="https://github.com/netty/netty/issues/2289">#2289</a>.
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*/
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Class<?> clazz = getClass();
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Map<Class<?>, Boolean> cache = InternalThreadLocalMap.get().handlerSharableCache();
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Boolean sharable = cache.get(clazz);
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if (sharable == null) {
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sharable = clazz.isAnnotationPresent(Sharable.class);
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if (!sharable) {
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AnnotatedType annotatedType = clazz.getAnnotatedSuperclass();
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sharable = annotatedType.isAnnotationPresent(Sharable.class);
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}
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cache.put(clazz, sharable);
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}
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return sharable;
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}
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}
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