io.netty.handler.codec.MessageToMessageEncoder Maven / Gradle / Ivy
/*
* Copyright 2012 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.handler.codec;
import io.netty.buffer.MessageBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelOutboundMessageHandlerAdapter;
/**
* {@link ChannelOutboundMessageHandlerAdapter} which encodes from one message to an other message
*
* For example here is an implementation which decodes an {@link Integer} to an {@link String}.
*
*
* public class IntegerToStringEncoder extends
* {@link MessageToMessageEncoder}<{@link Integer}> {
* public StringToIntegerDecoder() {
* super(String.class);
* }
*
* {@code @Override}
* public {@link Object} encode({@link ChannelHandlerContext} ctx, {@link Integer} message)
* throws {@link Exception} {
* return message.toString();
* }
* }
*
*
*/
public abstract class MessageToMessageEncoder extends ChannelOutboundMessageHandlerAdapter {
@Override
public final void flush(ChannelHandlerContext ctx, I msg) throws Exception {
try {
ctx.nextOutboundMessageBuffer().unfoldAndAdd(encode(ctx, msg));
} catch (CodecException e) {
throw e;
} catch (Exception e) {
throw new CodecException(e);
}
}
/**
* Encode from one message to an other. This method will be called till either the {@link MessageBuf} has nothing
* left or till this method returns {@code null}.
*
* @param ctx the {@link ChannelHandlerContext} which this {@link MessageToMessageEncoder} belongs to
* @param msg the message to encode to an other one
* @return message the encoded message or {@code null} if more messages are needed be cause the implementation
* needs to do some kind of aggragation
* @throws Exception is thrown if an error accour
*/
protected abstract Object encode(ChannelHandlerContext ctx, I msg) throws Exception;
}