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    • com.google.cloud.spring.pubsub.integration.inbound.PubSubMessageSource Maven / Gradle / Ivy

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    /*
 * Copyright 2017-2019 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
 *
 *      https://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.google.cloud.spring.pubsub.integration.inbound;

import com.google.cloud.spring.pubsub.core.subscriber.PubSubSubscriberOperations;
import com.google.cloud.spring.pubsub.integration.AckMode;
import com.google.cloud.spring.pubsub.integration.PubSubHeaderMapper;
import com.google.cloud.spring.pubsub.support.GcpPubSubHeaders;
import com.google.cloud.spring.pubsub.support.converter.ConvertedAcknowledgeablePubsubMessage;
import java.util.ArrayDeque;
import java.util.List;
import java.util.Map;
import org.springframework.integration.IntegrationMessageHeaderAccessor;
import org.springframework.integration.endpoint.AbstractFetchLimitingMessageSource;
import org.springframework.integration.endpoint.AbstractMessageSource;
import org.springframework.integration.mapping.HeaderMapper;
import org.springframework.integration.support.AbstractIntegrationMessageBuilder;
import org.springframework.messaging.Message;
import org.springframework.util.Assert;

/**
 * A PubSub
 * Synchronous pull implementation of {@link AbstractMessageSource}.
 *
 * @since 1.2
 */
public class PubSubMessageSource extends AbstractFetchLimitingMessageSource {

  private final String subscriptionName;

  private final PubSubSubscriberOperations pubSubSubscriberOperations;

  private AckMode ackMode = AckMode.AUTO;

  private HeaderMapper> headerMapper = new PubSubHeaderMapper();

  private Class payloadType = byte[].class;

  private boolean blockOnPull;

  private final ArrayDeque> cachedMessages =
      new ArrayDeque<>();

  /**
   * Instantiates a Pub/Sub inbound message adapter to poll a given subscription for messages.
   *
   * @param pubSubSubscriberOperations {@link PubSubSubscriberOperations} to use
   * @param subscriptionName short or fully qualified subscription name
   */
  public PubSubMessageSource(
      PubSubSubscriberOperations pubSubSubscriberOperations, String subscriptionName) {
    Assert.notNull(pubSubSubscriberOperations, "Pub/Sub subscriber template can't be null.");
    Assert.notNull(subscriptionName, "Pub/Sub subscription name can't be null.");
    this.pubSubSubscriberOperations = pubSubSubscriberOperations;
    this.subscriptionName = subscriptionName;
  }

  public void setAckMode(AckMode ackMode) {
    Assert.notNull(ackMode, "The acknowledgement mode can't be null.");
    this.ackMode = ackMode;
  }

  public void setPayloadType(Class payloadType) {
    Assert.notNull(payloadType, "The payload type cannot be null.");
    this.payloadType = payloadType;
  }

  public void setHeaderMapper(HeaderMapper> headerMapper) {
    Assert.notNull(headerMapper, "The header mapper can't be null.");
    this.headerMapper = headerMapper;
  }

  /**
   * Instructs synchronous pull to wait until at least one message is available.
   *
   * @param blockOnPull whether to block until a message is available
   */
  public void setBlockOnPull(boolean blockOnPull) {
    this.blockOnPull = blockOnPull;
  }

  /**
   * Provides a single polled message.
   *
   * 
    Messages are received from Pub/Sub by synchronous pull, in batches determined by {@code
   * fetchSize}.
   *
   * @param fetchSize number of messages to fetch from Pub/Sub.
   * @return {@link Message} wrapper containing the original message.
   */
  @Override
  protected Object doReceive(int fetchSize) {
    if (this.cachedMessages.isEmpty()) {
      Integer maxMessages = (fetchSize > 0) ? fetchSize : 1;

      List> messages =
          this.pubSubSubscriberOperations.pullAndConvert(
              this.subscriptionName, maxMessages, !this.blockOnPull, this.payloadType);
      if (messages.isEmpty()) {
        return null;
      } else if (messages.size() == 1) {
        // don't bother storing.
        return processMessage(messages.get(0));
      } else {
        this.cachedMessages.addAll(messages);
      }
    }

    return processMessage(this.cachedMessages.pollFirst());
  }

  @Override
  public String getComponentType() {
    return "gcp-pubsub:message-source";
  }

  /**
   * Applies header customizations and acknowledges the message, if necessary.
   *
   * 
    {@link AckMode#AUTO} and {@link AckMode#AUTO_ACK} result in automatic acking on success.
   * {@link AckMode#AUTO} results in automatic nacking on failure.
   *
   * @param message source Pub/Sub message.
   * @return {@link Message} wrapper containing the original message.
   */
  private AbstractIntegrationMessageBuilder processMessage(
      ConvertedAcknowledgeablePubsubMessage message) {
    if (message == null) {
      return null;
    }

    Map messageHeaders =
        this.headerMapper.toHeaders(message.getPubsubMessage().getAttributesMap());

    messageHeaders.put(GcpPubSubHeaders.ORIGINAL_MESSAGE, message);
    messageHeaders.put(
        IntegrationMessageHeaderAccessor.ACKNOWLEDGMENT_CALLBACK,
        new PubSubAcknowledgmentCallback(message, this.ackMode));

    return getMessageBuilderFactory().withPayload(message.getPayload()).copyHeaders(messageHeaders);
  }
}
    
    
    
    

    




    
    
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