org.springframework.cloud.stream.annotation.rxjava.SubjectMessageHandler.java Source code

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Here is the source code for org.springframework.cloud.stream.annotation.rxjava.SubjectMessageHandler.java

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/*
 * Copyright 2015-2016 the original author or authors.
 *
 * Licensed 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 org.springframework.cloud.stream.annotation.rxjava;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import rx.Observable;
import rx.Subscription;
import rx.functions.Action0;
import rx.functions.Action1;
import rx.subjects.PublishSubject;
import rx.subjects.SerializedSubject;
import rx.subjects.Subject;

import org.springframework.context.SmartLifecycle;
import org.springframework.integration.handler.AbstractMessageProducingHandler;
import org.springframework.messaging.Message;
import org.springframework.messaging.support.MessageBuilder;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;

/**
 * Adapts the item at a time delivery of a {@link org.springframework.messaging.MessageHandler}
 * by delegating processing to a {@link Observable}.
 * <p/>
 * The outputStream of the processor is used to create a message and send it to the output channel.  If the
 * input channel and output channel are connected to the {@link org.springframework.cloud.stream.binder.Binder},
 * then data delivered to the input stream via a call to onNext is invoked on the dispatcher thread of the binder
 * and sending a message to the output channel will involve IO operations on the binder.
 * <p/>
 * The implementation uses a SerializedSubject.  This has the advantage that the state of the Observabale
 * can be shared across all the incoming dispatcher threads that are invoking onNext.  It has the disadvantage
 * that processing and sending to the output channel will execute serially on one of the dispatcher threads.
 * <p/>
 * The use of this handler makes for a very natural first experience when processing data.  For example given
 * the stream <code></code>http | rxjava-processor | log</code> where the <code>rxjava-processor</code> does a
 * <code>buffer(5)</code> and then produces a single value.  Sending 10 messages to the http source will
 * result in 2 messages in the log, no matter how many dispatcher threads are used.
 * <p/>
 * You can modify what thread the outputStream subscriber, which does the send to the output channel,
 * will use by explicitly calling <code>observeOn</code> before returning the outputStream from your processor.
 * <p/>
    
 * All error handling is the responsibility of the processor implementation.
 *
 * @author Mark Pollack
 * @author Ilayaperumal Gopinathan
 * @author Marius Bogoevici
 */
@SuppressWarnings({ "unchecked", "rawtypes" })
@Deprecated
public class SubjectMessageHandler extends AbstractMessageProducingHandler implements SmartLifecycle {

    private final Log logger = LogFactory.getLog(getClass());

    @SuppressWarnings("rawtypes")
    private final RxJavaProcessor processor;

    private volatile Subject subject;

    private volatile Subscription subscription;

    private volatile boolean running;

    @SuppressWarnings({ "unchecked", "rawtypes" })
    public SubjectMessageHandler(RxJavaProcessor processor) {
        Assert.notNull(processor, "RxJava processor must not be null.");
        this.processor = processor;
    }

    @Override
    public synchronized void start() {
        if (!this.running) {
            this.subject = new SerializedSubject(PublishSubject.create());
            Observable<?> outputStream = this.processor.process(this.subject);
            this.subscription = outputStream.subscribe(new Action1<Object>() {

                @Override
                public void call(Object outputObject) {
                    if (ClassUtils.isAssignable(Message.class, outputObject.getClass())) {
                        getOutputChannel().send((Message) outputObject);
                    } else {
                        getOutputChannel().send(MessageBuilder.withPayload(outputObject).build());
                    }
                }
            }, new Action1<Throwable>() {

                @Override
                public void call(Throwable throwable) {
                    SubjectMessageHandler.this.logger.error(throwable.getMessage(), throwable);
                }
            }, new Action0() {

                @Override
                public void call() {
                    SubjectMessageHandler.this.logger
                            .info("Subscription close for [" + SubjectMessageHandler.this.subscription + "]");
                }
            });
            this.running = true;
        }
    }

    @Override
    public synchronized boolean isRunning() {
        return this.running;
    }

    @Override
    public boolean isAutoStartup() {
        return false;
    }

    @Override
    public void stop(Runnable callback) {
        if (this.running) {
            stop();
            if (callback != null) {
                callback.run();
            }
        }
    }

    @Override
    public int getPhase() {
        return 0;
    }

    @Override
    protected void handleMessageInternal(Message<?> message) throws Exception {
        this.subject.onNext(message.getPayload());
    }

    @Override
    public synchronized void stop() {
        if (this.running) {
            this.subject.onCompleted();
            this.subscription.unsubscribe();
            this.subscription = null;
            this.subject = null;
            this.running = false;
        }
    }
}