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JDBC Driver for Google Cloud Spanner
/*
* 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 nl.topicus.jdbc.shaded.io.netty.channel;
import nl.topicus.jdbc.shaded.io.netty.util.ReferenceCountUtil;
import nl.topicus.jdbc.shaded.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.
*
*
* 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);
* }
* }
*
*
* 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}.
*
* Forward compatibility notice
*
* Please keep in mind that {@link #channelRead0(ChannelHandlerContext, I)} will be renamed to
* {@code messageReceived(ChannelHandlerContext, I)} in 5.0.
*
*/
public abstract class SimpleChannelInboundHandler 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 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 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);
}
}
}
/**
* Please keep in mind that this method will be renamed to
* {@code messageReceived(ChannelHandlerContext, I)} in 5.0.
*
* 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;
}