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/*
* Copyright 2018 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.ReferenceCountUtil;
import io.netty.util.internal.TypeParameterMatcher;
/**
* {@link ChannelInboundHandlerAdapter} which allows to conveniently only handle a specific type of user events.
*
* For example, here is an implementation which only handle {@link String} user events.
*
*
* public class StringEventHandler extends
* {@link SimpleUserEventChannelHandler}<{@link String}> {
*
* {@code @Override}
* protected void eventReceived({@link ChannelHandlerContext} ctx, {@link String} evt)
* throws {@link Exception} {
* System.out.println(evt);
* }
* }
*
*
* Be aware that depending of the constructor parameters it will release all handled events by passing them to
* {@link ReferenceCountUtil#release(Object)}. In this case you may need to use
* {@link ReferenceCountUtil#retain(Object)} if you pass the object to the next handler in the {@link ChannelPipeline}.
*/
public abstract class SimpleUserEventChannelHandler extends ChannelInboundHandlerAdapter {
private final TypeParameterMatcher matcher;
private final boolean autoRelease;
/**
* see {@link #SimpleUserEventChannelHandler(boolean)} with {@code true} as boolean parameter.
*/
protected SimpleUserEventChannelHandler() {
this(true);
}
/**
* Create a new instance which will try to detect the types to match out of the type parameter of the class.
*
* @param autoRelease {@code true} if handled events should be released automatically by passing them to
* {@link ReferenceCountUtil#release(Object)}.
*/
protected SimpleUserEventChannelHandler(boolean autoRelease) {
matcher = TypeParameterMatcher.find(this, SimpleUserEventChannelHandler.class, "I");
this.autoRelease = autoRelease;
}
/**
* see {@link #SimpleUserEventChannelHandler(Class, boolean)} with {@code true} as boolean value.
*/
protected SimpleUserEventChannelHandler(Class eventType) {
this(eventType, true);
}
/**
* Create a new instance
*
* @param eventType The type of events to match
* @param autoRelease {@code true} if handled events should be released automatically by passing them to
* {@link ReferenceCountUtil#release(Object)}.
*/
protected SimpleUserEventChannelHandler(Class eventType, boolean autoRelease) {
matcher = TypeParameterMatcher.get(eventType);
this.autoRelease = autoRelease;
}
/**
* Returns {@code true} if the given user event should be handled. If {@code false} it will be passed to the next
* {@link ChannelInboundHandler} in the {@link ChannelPipeline}.
*/
protected boolean acceptEvent(Object evt) throws Exception {
return matcher.match(evt);
}
@Override
public final void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
boolean release = true;
try {
if (acceptEvent(evt)) {
@SuppressWarnings("unchecked")
I ievt = (I) evt;
eventReceived(ctx, ievt);
} else {
release = false;
ctx.fireUserEventTriggered(evt);
}
} finally {
if (autoRelease && release) {
ReferenceCountUtil.release(evt);
}
}
}
/**
* Is called for each user event triggered of type {@link I}.
*
* @param ctx the {@link ChannelHandlerContext} which this {@link SimpleUserEventChannelHandler} belongs to
* @param evt the user event to handle
*
* @throws Exception is thrown if an error occurred
*/
protected abstract void eventReceived(ChannelHandlerContext ctx, I evt) throws Exception;
}