/*
* 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.
ByteBuf;
import io.netty.channel.
ChannelDuplexHandler;
import io.netty.channel.
ChannelHandlerContext;
import io.netty.channel.
ChannelPromise;
import io.netty.util.internal.
TypeParameterMatcher;
import java.util.
List;
/**
* A Codec for on-the-fly encoding/decoding of bytes to messages and vise-versa.
*
* This can be thought of as a combination of {@link ByteToMessageDecoder} and {@link MessageToByteEncoder}.
*
* Be aware that sub-classes of {@link ByteToMessageCodec} <strong>MUST NOT</strong>
* annotated with {@link @Sharable}.
*/
public abstract class
ByteToMessageCodec<I> extends
ChannelDuplexHandler {
private final
TypeParameterMatcher outboundMsgMatcher;
private final
MessageToByteEncoder<I>
encoder;
private final
ByteToMessageDecoder decoder = new
ByteToMessageDecoder() {
@
Override
public void
decode(
ChannelHandlerContext ctx,
ByteBuf in,
List<
Object>
out) throws
Exception {
ByteToMessageCodec.this.
decode(
ctx,
in,
out);
}
@
Override
protected void
decodeLast(
ChannelHandlerContext ctx,
ByteBuf in,
List<
Object>
out) throws
Exception {
ByteToMessageCodec.this.
decodeLast(
ctx,
in,
out);
}
};
/**
* see {@link #ByteToMessageCodec(boolean)} with {@code true} as boolean parameter.
*/
protected
ByteToMessageCodec() {
this(true);
}
/**
* see {@link #ByteToMessageCodec(Class, boolean)} with {@code true} as boolean value.
*/
protected
ByteToMessageCodec(
Class<? extends I>
outboundMessageType) {
this(
outboundMessageType, true);
}
/**
* Create a new instance which will try to detect the types to match out of the type parameter of the class.
*
* @param preferDirect {@code true} if a direct {@link ByteBuf} should be tried to be used as target for
* the encoded messages. If {@code false} is used it will allocate a heap
* {@link ByteBuf}, which is backed by an byte array.
*/
protected
ByteToMessageCodec(boolean
preferDirect) {
ensureNotSharable();
outboundMsgMatcher =
TypeParameterMatcher.
find(this,
ByteToMessageCodec.class, "I");
encoder = new
Encoder(
preferDirect);
}
/**
* Create a new instance
*
* @param outboundMessageType The type of messages to match
* @param preferDirect {@code true} if a direct {@link ByteBuf} should be tried to be used as target for
* the encoded messages. If {@code false} is used it will allocate a heap
* {@link ByteBuf}, which is backed by an byte array.
*/
protected
ByteToMessageCodec(
Class<? extends I>
outboundMessageType, boolean
preferDirect) {
ensureNotSharable();
outboundMsgMatcher =
TypeParameterMatcher.
get(
outboundMessageType);
encoder = new
Encoder(
preferDirect);
}
/**
* Returns {@code true} if and only if the specified message can be encoded by this codec.
*
* @param msg the message
*/
public boolean
acceptOutboundMessage(
Object msg) throws
Exception {
return
outboundMsgMatcher.
match(
msg);
}
@
Override
public void
channelRead(
ChannelHandlerContext ctx,
Object msg) throws
Exception {
decoder.
channelRead(
ctx,
msg);
}
@
Override
public void
write(
ChannelHandlerContext ctx,
Object msg,
ChannelPromise promise) throws
Exception {
encoder.
write(
ctx,
msg,
promise);
}
@
Override
public void
channelReadComplete(
ChannelHandlerContext ctx) throws
Exception {
decoder.
channelReadComplete(
ctx);
}
@
Override
public void
channelInactive(
ChannelHandlerContext ctx) throws
Exception {
decoder.
channelInactive(
ctx);
}
@
Override
public void
handlerAdded(
ChannelHandlerContext ctx) throws
Exception {
try {
decoder.
handlerAdded(
ctx);
} finally {
encoder.
handlerAdded(
ctx);
}
}
@
Override
public void
handlerRemoved(
ChannelHandlerContext ctx) throws
Exception {
try {
decoder.
handlerRemoved(
ctx);
} finally {
encoder.
handlerRemoved(
ctx);
}
}
/**
* @see MessageToByteEncoder#encode(ChannelHandlerContext, Object, ByteBuf)
*/
protected abstract void
encode(
ChannelHandlerContext ctx, I
msg,
ByteBuf out) throws
Exception;
/**
* @see ByteToMessageDecoder#decode(ChannelHandlerContext, ByteBuf, List)
*/
protected abstract void
decode(
ChannelHandlerContext ctx,
ByteBuf in,
List<
Object>
out) throws
Exception;
/**
* @see ByteToMessageDecoder#decodeLast(ChannelHandlerContext, ByteBuf, List)
*/
protected void
decodeLast(
ChannelHandlerContext ctx,
ByteBuf in,
List<
Object>
out) throws
Exception {
if (
in.
isReadable()) {
// Only call decode() if there is something left in the buffer to decode.
// See https://github.com/netty/netty/issues/4386
decode(
ctx,
in,
out);
}
}
private final class
Encoder extends
MessageToByteEncoder<I> {
Encoder(boolean
preferDirect) {
super(
preferDirect);
}
@
Override
public boolean
acceptOutboundMessage(
Object msg) throws
Exception {
return
ByteToMessageCodec.this.
acceptOutboundMessage(
msg);
}
@
Override
protected void
encode(
ChannelHandlerContext ctx, I
msg,
ByteBuf out) throws
Exception {
ByteToMessageCodec.this.
encode(
ctx,
msg,
out);
}
}
}