io.netty.channel.ChannelHandlerAdapter Maven / Gradle / Ivy
/*
* Copyright 2013 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.channel;
import io.netty.util.internal.InternalThreadLocalMap;
import java.util.Map;
/**
* Skeleton implementation of a {@link ChannelHandler}.
*/
public abstract class ChannelHandlerAdapter implements ChannelHandler {
// Not using volatile because it's used only for a sanity check.
boolean added;
/**
* Throws {@link IllegalStateException} if {@link ChannelHandlerAdapter#isSharable()} returns {@code true}
*/
protected void ensureNotSharable() {
if (isSharable()) {
throw new IllegalStateException("ChannelHandler " + getClass().getName() + " is not allowed to be shared");
}
}
/**
* Return {@code true} if the implementation is {@link Sharable} and so can be added
* to different {@link ChannelPipeline}s.
*/
public boolean isSharable() {
/**
* Cache the result of {@link Sharable} annotation detection to workaround a condition. We use a
* {@link ThreadLocal} and {@link WeakHashMap} to eliminate the volatile write/reads. Using different
* {@link WeakHashMap} instances per {@link Thread} is good enough for us and the number of
* {@link Thread}s are quite limited anyway.
*
* See #2289.
*/
Class clazz = getClass();
Map, Boolean> cache = InternalThreadLocalMap.get().handlerSharableCache();
Boolean sharable = cache.get(clazz);
if (sharable == null) {
sharable = clazz.isAnnotationPresent(Sharable.class);
cache.put(clazz, sharable);
}
return sharable;
}
/**
* Do nothing by default, sub-classes may override this method.
*/
@Override
public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
// NOOP
}
/**
* Do nothing by default, sub-classes may override this method.
*/
@Override
public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
// NOOP
}
/**
* Calls {@link ChannelHandlerContext#fireExceptionCaught(Throwable)} to forward
* to the next {@link ChannelHandler} in the {@link ChannelPipeline}.
*
* Sub-classes may override this method to change behavior.
*/
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
ctx.fireExceptionCaught(cause);
}
}