alluxio.client.netty.ClientHandler.java Source code

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Here is the source code for alluxio.client.netty.ClientHandler.java

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/*
 * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
 * (the "License"). You may not use this work except in compliance with the License, which is
 * available at www.apache.org/licenses/LICENSE-2.0
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied, as more fully set forth in the License.
 *
 * See the NOTICE file distributed with this work for information regarding copyright ownership.
 */

package alluxio.client.netty;

import alluxio.Constants;
import alluxio.exception.ExceptionMessage;
import alluxio.network.protocol.RPCMessage;
import alluxio.network.protocol.RPCResponse;

import com.google.common.base.Preconditions;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.util.HashSet;
import java.util.Set;

import javax.annotation.concurrent.NotThreadSafe;

/**
 * This handles all the messages received by the client channel.
 */
@ChannelHandler.Sharable
@NotThreadSafe
public final class ClientHandler extends SimpleChannelInboundHandler<RPCMessage> {
    private static final Logger LOG = LoggerFactory.getLogger(Constants.LOGGER_TYPE);

    /**
     * The interface for listeners to implement to receive callbacks when messages are received.
     */
    public interface ResponseListener {
        /**
         * This method will be called when a message is received on the client.
         *
         * @param response the RPC response
         */
        void onResponseReceived(RPCResponse response);
    }

    private final Set<ResponseListener> mListeners;

    /**
     * Creates a new {@link ClientHandler}.
     */
    public ClientHandler() {
        mListeners = new HashSet<>(4);
    }

    /**
     * Adds a {@link ResponseListener} listener to the client handler.
     *
     * @param listener the listener to add
     */
    public void addListener(ResponseListener listener) {
        mListeners.add(Preconditions.checkNotNull(listener));
    }

    /**
     * Removes a {@link ResponseListener} listener from the client handler.
     *
     * @param listener the listener to remove
     */
    public void removeListener(ResponseListener listener) {
        mListeners.remove(listener);
    }

    @Override
    public void channelRead0(final ChannelHandlerContext ctx, final RPCMessage msg) throws IOException {
        if (msg instanceof RPCResponse) {
            handleResponse((RPCResponse) msg);
        } else {
            // The client should only receive RPCResponse messages.
            throw new IllegalArgumentException(ExceptionMessage.NO_RPC_HANDLER.getMessage(msg.getType()));
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        LOG.warn("Exception thrown while processing request", cause);
        ctx.close();
    }

    private void handleResponse(final RPCResponse resp) throws IOException {
        for (ResponseListener listener : mListeners) {
            listener.onResponseReceived(resp);
        }
    }
}