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Java example source code file (EmbeddedChannel.java)

This example Java source code file (EmbeddedChannel.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstractunsafe, channelconfig, channelfuture, channelhandler, channelmetadata, defaultunsafe, embeddedchannel, embeddedchannelpipeline, embeddedeventloop, exception, net, network, object, override, queue, socketaddress, util

The EmbeddedChannel.java Java example source code

/*
 * 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.channel.embedded;

import io.netty.channel.AbstractChannel;
import io.netty.channel.Channel;
import io.netty.channel.ChannelConfig;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelId;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelMetadata;
import io.netty.channel.ChannelOutboundBuffer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.ChannelPromise;
import io.netty.channel.DefaultChannelConfig;
import io.netty.channel.DefaultChannelPipeline;
import io.netty.channel.EventLoop;
import io.netty.util.ReferenceCountUtil;
import io.netty.util.internal.ObjectUtil;
import io.netty.util.internal.PlatformDependent;
import io.netty.util.internal.RecyclableArrayList;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;

import java.net.SocketAddress;
import java.nio.channels.ClosedChannelException;
import java.util.ArrayDeque;
import java.util.Queue;

/**
 * Base class for {@link Channel} implementations that are used in an embedded fashion.
 */
public class EmbeddedChannel extends AbstractChannel {

    private static final SocketAddress LOCAL_ADDRESS = new EmbeddedSocketAddress();
    private static final SocketAddress REMOTE_ADDRESS = new EmbeddedSocketAddress();

    private static final ChannelHandler[] EMPTY_HANDLERS = new ChannelHandler[0];
    private enum State { OPEN, ACTIVE, CLOSED }

    private static final InternalLogger logger = InternalLoggerFactory.getInstance(EmbeddedChannel.class);

    private static final ChannelMetadata METADATA_NO_DISCONNECT = new ChannelMetadata(false);
    private static final ChannelMetadata METADATA_DISCONNECT = new ChannelMetadata(true);

    private final EmbeddedEventLoop loop = new EmbeddedEventLoop();
    private final ChannelFutureListener recordExceptionListener = new ChannelFutureListener() {
        @Override
        public void operationComplete(ChannelFuture future) throws Exception {
            recordException(future);
        }
    };

    private final ChannelMetadata metadata;
    private final ChannelConfig config;

    private Queue<Object> inboundMessages;
    private Queue<Object> outboundMessages;
    private Throwable lastException;
    private State state;

    /**
     * Create a new instance with an {@link EmbeddedChannelId} and an empty pipeline.
     */
    public EmbeddedChannel() {
        this(EMPTY_HANDLERS);
    }

    /**
     * Create a new instance with the specified ID and an empty pipeline.
     *
     * @param channelId the {@link ChannelId} that will be used to identify this channel
     */
    public EmbeddedChannel(ChannelId channelId) {
        this(channelId, EMPTY_HANDLERS);
    }

    /**
     * Create a new instance with the pipeline initialized with the specified handlers.
     *
     * @param handlers the {@link ChannelHandler}s which will be add in the {@link ChannelPipeline}
     */
    public EmbeddedChannel(ChannelHandler... handlers) {
        this(EmbeddedChannelId.INSTANCE, handlers);
    }

    /**
     * Create a new instance with the pipeline initialized with the specified handlers.
     *
     * @param hasDisconnect {@code false} if this {@link Channel} will delegate {@link #disconnect()}
     *                      to {@link #close()}, {@link false} otherwise.
     * @param handlers the {@link ChannelHandler}s which will be add in the {@link ChannelPipeline}
     */
    public EmbeddedChannel(boolean hasDisconnect, ChannelHandler... handlers) {
        this(EmbeddedChannelId.INSTANCE, hasDisconnect, handlers);
    }

    /**
     * Create a new instance with the channel ID set to the given ID and the pipeline
     * initialized with the specified handlers.
     *
     * @param channelId the {@link ChannelId} that will be used to identify this channel
     * @param handlers the {@link ChannelHandler}s which will be add in the {@link ChannelPipeline}
     */
    public EmbeddedChannel(ChannelId channelId, final ChannelHandler... handlers) {
        this(channelId, false, handlers);
    }

    /**
     * Create a new instance with the channel ID set to the given ID and the pipeline
     * initialized with the specified handlers.
     *
     * @param channelId the {@link ChannelId} that will be used to identify this channel
     * @param hasDisconnect {@code false} if this {@link Channel} will delegate {@link #disconnect()}
     *                      to {@link #close()}, {@link false} otherwise.
     * @param handlers the {@link ChannelHandler}s which will be add in the {@link ChannelPipeline}
     */
    public EmbeddedChannel(ChannelId channelId, boolean hasDisconnect, final ChannelHandler... handlers) {
        super(null, channelId);
        metadata = metadata(hasDisconnect);
        config = new DefaultChannelConfig(this);
        setup(handlers);
    }

    /**
     * Create a new instance with the channel ID set to the given ID and the pipeline
     * initialized with the specified handlers.
     *
     * @param channelId the {@link ChannelId} that will be used to identify this channel
     * @param hasDisconnect {@code false} if this {@link Channel} will delegate {@link #disconnect()}
     *                      to {@link #close()}, {@link false} otherwise.
     * @param config the {@link ChannelConfig} which will be returned by {@link #config()}.
     * @param handlers the {@link ChannelHandler}s which will be add in the {@link ChannelPipeline}
     */
    public EmbeddedChannel(ChannelId channelId, boolean hasDisconnect, final ChannelConfig config,
                           final ChannelHandler... handlers) {
        super(null, channelId);
        metadata = metadata(hasDisconnect);
        this.config = ObjectUtil.checkNotNull(config, "config");
        setup(handlers);
    }

    private static ChannelMetadata metadata(boolean hasDisconnect) {
        return hasDisconnect ? METADATA_DISCONNECT : METADATA_NO_DISCONNECT;
    }

    private void setup(final ChannelHandler... handlers) {
        ObjectUtil.checkNotNull(handlers, "handlers");
        ChannelPipeline p = pipeline();
        p.addLast(new ChannelInitializer<Channel>() {
            @Override
            protected void initChannel(Channel ch) throws Exception {
                ChannelPipeline pipeline = ch.pipeline();
                for (ChannelHandler h: handlers) {
                    if (h == null) {
                        break;
                    }
                    pipeline.addLast(h);
                }
            }
        });

        ChannelFuture future = loop.register(this);
        assert future.isDone();
    }

    @Override
    protected final DefaultChannelPipeline newChannelPipeline() {
        return new EmbeddedChannelPipeline(this);
    }

    @Override
    public ChannelMetadata metadata() {
        return metadata;
    }

    @Override
    public ChannelConfig config() {
        return config;
    }

    @Override
    public boolean isOpen() {
        return state != State.CLOSED;
    }

    @Override
    public boolean isActive() {
        return state == State.ACTIVE;
    }

    /**
     * Returns the {@link Queue} which holds all the {@link Object}s that were received by this {@link Channel}.
     */
    public Queue<Object> inboundMessages() {
        if (inboundMessages == null) {
            inboundMessages = new ArrayDeque<Object>();
        }
        return inboundMessages;
    }

    /**
     * @deprecated use {@link #inboundMessages()}
     */
    @Deprecated
    public Queue<Object> lastInboundBuffer() {
        return inboundMessages();
    }

    /**
     * Returns the {@link Queue} which holds all the {@link Object}s that were written by this {@link Channel}.
     */
    public Queue<Object> outboundMessages() {
        if (outboundMessages == null) {
            outboundMessages = new ArrayDeque<Object>();
        }
        return outboundMessages;
    }

    /**
     * @deprecated use {@link #outboundMessages()}
     */
    @Deprecated
    public Queue<Object> lastOutboundBuffer() {
        return outboundMessages();
    }

    /**
     * Return received data from this {@link Channel}
     */
    @SuppressWarnings("unchecked")
    public <T> T readInbound() {
        return (T) poll(inboundMessages);
    }

    /**
     * Read data from the outbound. This may return {@code null} if nothing is readable.
     */
    @SuppressWarnings("unchecked")
    public <T> T readOutbound() {
        return (T) poll(outboundMessages);
    }

    /**
     * Write messages to the inbound of this {@link Channel}.
     *
     * @param msgs the messages to be written
     *
     * @return {@code true} if the write operation did add something to the inbound buffer
     */
    public boolean writeInbound(Object... msgs) {
        ensureOpen();
        if (msgs.length == 0) {
            return isNotEmpty(inboundMessages);
        }

        ChannelPipeline p = pipeline();
        for (Object m: msgs) {
            p.fireChannelRead(m);
        }
        p.fireChannelReadComplete();
        runPendingTasks();
        checkException();
        return isNotEmpty(inboundMessages);
    }

    /**
     * Write messages to the outbound of this {@link Channel}.
     *
     * @param msgs              the messages to be written
     * @return bufferReadable   returns {@code true} if the write operation did add something to the outbound buffer
     */
    public boolean writeOutbound(Object... msgs) {
        ensureOpen();
        if (msgs.length == 0) {
            return isNotEmpty(outboundMessages);
        }

        RecyclableArrayList futures = RecyclableArrayList.newInstance(msgs.length);
        try {
            for (Object m: msgs) {
                if (m == null) {
                    break;
                }
                futures.add(write(m));
            }
            // We need to call runPendingTasks first as a ChannelOutboundHandler may used eventloop.execute(...) to
            // delay the write on the next eventloop run.
            runPendingTasks();
            flush();

            int size = futures.size();
            for (int i = 0; i < size; i++) {
                ChannelFuture future = (ChannelFuture) futures.get(i);
                if (future.isDone()) {
                    recordException(future);
                } else {
                    // The write may be delayed to run later by runPendingTasks()
                    future.addListener(recordExceptionListener);
                }
            }

            checkException();
            return isNotEmpty(outboundMessages);
        } finally {
            futures.recycle();
        }
    }

    /**
     * Mark this {@link Channel} as finished. Any futher try to write data to it will fail.
     *
     * @return bufferReadable returns {@code true} if any of the used buffers has something left to read
     */
    public boolean finish() {
        return finish(false);
    }

    /**
     * Mark this {@link Channel} as finished and release all pending message in the inbound and outbound buffer.
     * Any futher try to write data to it will fail.
     *
     * @return bufferReadable returns {@code true} if any of the used buffers has something left to read
     */
    public boolean finishAndReleaseAll() {
        return finish(true);
    }

    /**
     * Mark this {@link Channel} as finished. Any futher try to write data to it will fail.
     *
     * @param releaseAll if {@code true} all pending message in the inbound and outbound buffer are released.
     * @return bufferReadable returns {@code true} if any of the used buffers has something left to read
     */
    private boolean finish(boolean releaseAll) {
        close();
        try {
            checkException();
            return isNotEmpty(inboundMessages) || isNotEmpty(outboundMessages);
        } finally {
            if (releaseAll) {
                releaseAll(inboundMessages);
                releaseAll(outboundMessages);
            }
        }
    }

    /**
     * Release all buffered inbound messages and return {@code true} if any were in the inbound buffer, {@code false}
     * otherwise.
     */
    public boolean releaseInbound() {
        return releaseAll(inboundMessages);
    }

    /**
     * Release all buffered outbound messages and return {@code true} if any were in the outbound buffer, {@code false}
     * otherwise.
     */
    public boolean releaseOutbound() {
        return releaseAll(outboundMessages);
    }

    private static boolean releaseAll(Queue<Object> queue) {
        if (isNotEmpty(queue)) {
            for (;;) {
                Object msg = queue.poll();
                if (msg == null) {
                    break;
                }
                ReferenceCountUtil.release(msg);
            }
            return true;
        }
        return false;
    }

    private void finishPendingTasks(boolean cancel) {
        runPendingTasks();
        if (cancel) {
            // Cancel all scheduled tasks that are left.
            loop.cancelScheduledTasks();
        }
    }

    @Override
    public final ChannelFuture close() {
        return close(newPromise());
    }

    @Override
    public final ChannelFuture disconnect() {
        return disconnect(newPromise());
    }

    @Override
    public final ChannelFuture close(ChannelPromise promise) {
        // We need to call runPendingTasks() before calling super.close() as there may be something in the queue
        // that needs to be run before the actual close takes place.
        runPendingTasks();
        ChannelFuture future = super.close(promise);

        // Now finish everything else and cancel all scheduled tasks that were not ready set.
        finishPendingTasks(true);
        return future;
    }

    @Override
    public final ChannelFuture disconnect(ChannelPromise promise) {
        ChannelFuture future = super.disconnect(promise);
        finishPendingTasks(!metadata.hasDisconnect());
        return future;
    }

    private static boolean isNotEmpty(Queue<Object> queue) {
        return queue != null && !queue.isEmpty();
    }

    private static Object poll(Queue<Object> queue) {
        return queue != null ? queue.poll() : null;
    }

    /**
     * Run all tasks (which also includes scheduled tasks) that are pending in the {@link EventLoop}
     * for this {@link Channel}
     */
    public void runPendingTasks() {
        try {
            loop.runTasks();
        } catch (Exception e) {
            recordException(e);
        }

        try {
            loop.runScheduledTasks();
        } catch (Exception e) {
            recordException(e);
        }
    }

    /**
     * Run all pending scheduled tasks in the {@link EventLoop} for this {@link Channel} and return the
     * {@code nanoseconds} when the next scheduled task is ready to run. If no other task was scheduled it will return
     * {@code -1}.
     */
    public long runScheduledPendingTasks() {
        try {
            return loop.runScheduledTasks();
        } catch (Exception e) {
            recordException(e);
            return loop.nextScheduledTask();
        }
    }

    private void recordException(ChannelFuture future) {
        if (!future.isSuccess()) {
            recordException(future.cause());
        }
    }

    private void recordException(Throwable cause) {
        if (lastException == null) {
            lastException = cause;
        } else {
            logger.warn(
                    "More than one exception was raised. " +
                            "Will report only the first one and log others.", cause);
        }
    }

    /**
     * Check if there was any {@link Throwable} received and if so rethrow it.
     */
    public void checkException() {
        Throwable t = lastException;
        if (t == null) {
            return;
        }

        lastException = null;

        PlatformDependent.throwException(t);
    }

    /**
     * Ensure the {@link Channel} is open and of not throw an exception.
     */
    protected final void ensureOpen() {
        if (!isOpen()) {
            recordException(new ClosedChannelException());
            checkException();
        }
    }

    @Override
    protected boolean isCompatible(EventLoop loop) {
        return loop instanceof EmbeddedEventLoop;
    }

    @Override
    protected SocketAddress localAddress0() {
        return isActive()? LOCAL_ADDRESS : null;
    }

    @Override
    protected SocketAddress remoteAddress0() {
        return isActive()? REMOTE_ADDRESS : null;
    }

    @Override
    protected void doRegister() throws Exception {
        state = State.ACTIVE;
    }

    @Override
    protected void doBind(SocketAddress localAddress) throws Exception {
        // NOOP
    }

    @Override
    protected void doDisconnect() throws Exception {
        if (!metadata.hasDisconnect()) {
            doClose();
        }
    }

    @Override
    protected void doClose() throws Exception {
        state = State.CLOSED;
    }

    @Override
    protected void doBeginRead() throws Exception {
        // NOOP
    }

    @Override
    protected AbstractUnsafe newUnsafe() {
        return new DefaultUnsafe();
    }

    @Override
    protected void doWrite(ChannelOutboundBuffer in) throws Exception {
        for (;;) {
            Object msg = in.current();
            if (msg == null) {
                break;
            }

            ReferenceCountUtil.retain(msg);
            outboundMessages().add(msg);
            in.remove();
        }
    }

    private class DefaultUnsafe extends AbstractUnsafe {
        @Override
        public void connect(SocketAddress remoteAddress, SocketAddress localAddress, ChannelPromise promise) {
            safeSetSuccess(promise);
        }
    }

    private final class EmbeddedChannelPipeline extends DefaultChannelPipeline {
        public EmbeddedChannelPipeline(EmbeddedChannel channel) {
            super(channel);
        }

        @Override
        protected void onUnhandledInboundException(Throwable cause) {
            recordException(cause);
        }

        @Override
        protected void onUnhandledInboundMessage(Object msg) {
            inboundMessages().add(msg);
        }
    }
}

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