com.github.sparkfy.network.protocol.MessageEncoder.java Source code

Introduction

Here is the source code for com.github.sparkfy.network.protocol.MessageEncoder.java

Source

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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 com.github.sparkfy.network.protocol;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageEncoder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;

/**
 * Encoder used by the server side to encode server-to-client responses.
 * This encoder is stateless so it is safe to be shared by multiple threads.
 */
@ChannelHandler.Sharable
public final class MessageEncoder extends MessageToMessageEncoder<Message> {

    private final Logger logger = LoggerFactory.getLogger(MessageEncoder.class);

    /***
     * Encodes a Message by invoking its encode() method. For non-data messages, we will add one
     * ByteBuf to 'out' containing the total frame length, the message type, and the message itself.
     * In the case of a ChunkFetchSuccess, we will also add the ManagedBuffer corresponding to the
     * data to 'out', in order to enable zero-copy transfer.
     */
    @Override
    public void encode(ChannelHandlerContext ctx, Message in, List<Object> out) throws Exception {
        Object body = null;
        long bodyLength = 0;
        boolean isBodyInFrame = false;

        // If the message has a body, take it out to enable zero-copy transfer for the payload.
        if (in.body() != null) {
            try {
                bodyLength = in.body().size();
                body = in.body().convertToNetty();
                isBodyInFrame = in.isBodyInFrame();
            } catch (Exception e) {
                in.body().release();
                if (in instanceof AbstractResponseMessage) {
                    AbstractResponseMessage resp = (AbstractResponseMessage) in;
                    // Re-encode this message as a failure response.
                    String error = e.getMessage() != null ? e.getMessage() : "null";
                    logger.error(
                            String.format("Error processing %s for client %s", in, ctx.channel().remoteAddress()),
                            e);
                    encode(ctx, resp.createFailureResponse(error), out);
                } else {
                    throw e;
                }
                return;
            }
        }

        Message.Type msgType = in.type();
        // All messages have the frame length, message type, and message itself. The frame length
        // may optionally include the length of the body data, depending on what message is being
        // sent.
        int headerLength = 8 + msgType.encodedLength() + in.encodedLength();
        long frameLength = headerLength + (isBodyInFrame ? bodyLength : 0);
        ByteBuf header = ctx.alloc().heapBuffer(headerLength);
        header.writeLong(frameLength);
        msgType.encode(header);
        in.encode(header);
        assert header.writableBytes() == 0;

        if (body != null) {
            // We transfer ownership of the reference on in.body() to MessageWithHeader.
            // This reference will be freed when MessageWithHeader.deallocate() is called.
            out.add(new MessageWithHeader(in.body(), header, body, bodyLength));
        } else {
            out.add(header);
        }
    }

}