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今天就跟大家聊聊有關(guān)rocketmq中MessageQueueSelector的作用是什么，可能很多人都不太了解，為了讓大家更加了解，小編給大家總結(jié)了以下內(nèi)容，希望大家根據(jù)這篇文章可以有所收獲。

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MessageQueueSelector

rocketmq-client-4.5.2-sources.jar!/org/apache/rocketmq/client/producer/MessageQueueSelector.java

public interface MessageQueueSelector {
    MessageQueue select(final List mqs, final Message msg, final Object arg);
}

• MessageQueueSelector接口定義了select方法，返回MessageQueue；它有幾個實現(xiàn)類，分別是SelectMessageQueueByHash、SelectMessageQueueByRandom、SelectMessageQueueByMachineRoom

SelectMessageQueueByHash

rocketmq-client-4.5.2-sources.jar!/org/apache/rocketmq/client/producer/selector/SelectMessageQueueByHash.java

public class SelectMessageQueueByHash implements MessageQueueSelector {

    @Override
    public MessageQueue select(List mqs, Message msg, Object arg) {
        int value = arg.hashCode();
        if (value < 0) {
            value = Math.abs(value);
        }

        value = value % mqs.size();
        return mqs.get(value);
    }
}

• SelectMessageQueueByHash實現(xiàn)了MessageQueueSelector接口，其select方法取arg參數(shù)的hashcode的絕對值，然后對mqs.size()取余，得到目標隊列在mqs的下標

SelectMessageQueueByRandom

rocketmq-client-4.5.2-sources.jar!/org/apache/rocketmq/client/producer/selector/SelectMessageQueueByRandom.java

public class SelectMessageQueueByRandom implements MessageQueueSelector {
    private Random random = new Random(System.currentTimeMillis());

    @Override
    public MessageQueue select(List mqs, Message msg, Object arg) {
        int value = random.nextInt(mqs.size());
        return mqs.get(value);
    }
}

• SelectMessageQueueByRandom實現(xiàn)了MessageQueueSelector接口，其select方法直接根據(jù)mqs.size()隨機一個值作為目標隊列在mqs的下標

SelectMessageQueueByMachineRoom

rocketmq-client-4.5.2-sources.jar!/org/apache/rocketmq/client/producer/selector/SelectMessageQueueByMachineRoom.java

public class SelectMessageQueueByMachineRoom implements MessageQueueSelector {
    private Set consumeridcs;

    @Override
    public MessageQueue select(List mqs, Message msg, Object arg) {
        return null;
    }

    public Set getConsumeridcs() {
        return consumeridcs;
    }

    public void setConsumeridcs(Set consumeridcs) {
        this.consumeridcs = consumeridcs;
    }
}

• SelectMessageQueueByMachineRoom實現(xiàn)了MessageQueueSelector接口，其select方法目前返回null

RocketMQTemplate

rocketmq-spring-boot-2.0.3-sources.jar!/org/apache/rocketmq/spring/core/RocketMQTemplate.java

public class RocketMQTemplate extends AbstractMessageSendingTemplate implements InitializingBean, DisposableBean {
    private static final  Logger log = LoggerFactory.getLogger(RocketMQTemplate.class);

    private DefaultMQProducer producer;

    private ObjectMapper objectMapper;

    private String charset = "UTF-8";

    private MessageQueueSelector messageQueueSelector = new SelectMessageQueueByHash();

    private final Map cache = new ConcurrentHashMap<>(); //only put TransactionMQProducer by now!!!

    public DefaultMQProducer getProducer() {
        return producer;
    }

    public void setProducer(DefaultMQProducer producer) {
        this.producer = producer;
    }

    public ObjectMapper getObjectMapper() {
        return objectMapper;
    }

    public void setObjectMapper(ObjectMapper objectMapper) {
        this.objectMapper = objectMapper;
    }

    public String getCharset() {
        return charset;
    }

    public void setCharset(String charset) {
        this.charset = charset;
    }

    public MessageQueueSelector getMessageQueueSelector() {
        return messageQueueSelector;
    }

    public void setMessageQueueSelector(MessageQueueSelector messageQueueSelector) {
        this.messageQueueSelector = messageQueueSelector;
    }

    //......
}

• RocketMQTemplate默認創(chuàng)建的MessageQueueSelector是SelectMessageQueueByHash

看完上述內(nèi)容，你們對rocketmq中MessageQueueSelector的作用是什么有進一步的了解嗎？如果還想了解更多知識或者相關(guān)內(nèi)容，請關(guān)注創(chuàng)新互聯(lián)行業(yè)資訊頻道，感謝大家的支持。

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