/*
* 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.
ReferenceCountUtil;
import io.netty.util.internal.
TypeParameterMatcher;
/**
* {@link ChannelInboundHandlerAdapter} which allows to explicit only handle a specific type of messages.
*
* For example here is an implementation which only handle {@link String} messages.
*
* <pre>
* public class StringHandler extends
* {@link SimpleChannelInboundHandler}<{@link String}> {
*
* {@code @Override}
* protected void channelRead0({@link ChannelHandlerContext} ctx, {@link String} message)
* throws {@link Exception} {
* System.out.println(message);
* }
* }
* </pre>
*
* Be aware that depending of the constructor parameters it will release all handled messages 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}.
*
* <h3>Forward compatibility notice</h3>
* <p>
* Please keep in mind that {@link #channelRead0(ChannelHandlerContext, I)} will be renamed to
* {@code messageReceived(ChannelHandlerContext, I)} in 5.0.
* </p>
*/
public abstract class
SimpleChannelInboundHandler<I> extends
ChannelInboundHandlerAdapter {
private final
TypeParameterMatcher matcher;
private final boolean
autoRelease;
/**
* see {@link #SimpleChannelInboundHandler(boolean)} with {@code true} as boolean parameter.
*/
protected
SimpleChannelInboundHandler() {
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 messages should be released automatically by passing them to
* {@link ReferenceCountUtil#release(Object)}.
*/
protected
SimpleChannelInboundHandler(boolean
autoRelease) {
matcher =
TypeParameterMatcher.
find(this,
SimpleChannelInboundHandler.class, "I");
this.
autoRelease =
autoRelease;
}
/**
* see {@link #SimpleChannelInboundHandler(Class, boolean)} with {@code true} as boolean value.
*/
protected
SimpleChannelInboundHandler(
Class<? extends I>
inboundMessageType) {
this(
inboundMessageType, true);
}
/**
* Create a new instance
*
* @param inboundMessageType The type of messages to match
* @param autoRelease {@code true} if handled messages should be released automatically by passing them to
* {@link ReferenceCountUtil#release(Object)}.
*/
protected
SimpleChannelInboundHandler(
Class<? extends I>
inboundMessageType, boolean
autoRelease) {
matcher =
TypeParameterMatcher.
get(
inboundMessageType);
this.
autoRelease =
autoRelease;
}
/**
* Returns {@code true} if the given message should be handled. If {@code false} it will be passed to the next
* {@link ChannelInboundHandler} in the {@link ChannelPipeline}.
*/
public boolean
acceptInboundMessage(
Object msg) throws
Exception {
return
matcher.
match(
msg);
}
@
Override
public void
channelRead(
ChannelHandlerContext ctx,
Object msg) throws
Exception {
boolean
release = true;
try {
if (
acceptInboundMessage(
msg)) {
@
SuppressWarnings("unchecked")
I
imsg = (I)
msg;
channelRead0(
ctx,
imsg);
} else {
release = false;
ctx.
fireChannelRead(
msg);
}
} finally {
if (
autoRelease &&
release) {
ReferenceCountUtil.
release(
msg);
}
}
}
/**
* <strong>Please keep in mind that this method will be renamed to
* {@code messageReceived(ChannelHandlerContext, I)} in 5.0.</strong>
*
* Is called for each message of type {@link I}.
*
* @param ctx the {@link ChannelHandlerContext} which this {@link SimpleChannelInboundHandler}
* belongs to
* @param msg the message to handle
* @throws Exception is thrown if an error occurred
*/
protected abstract void
channelRead0(
ChannelHandlerContext ctx, I
msg) throws
Exception;
}