Rocketmq的tag过滤和sql过滤

    rocketmq支持两种方式的消息过滤。

    1.tag过滤 （可以根据表达式来过滤tag）

       

consumer.subscribe("topic10", "*");

    2.根据自定义属性进行过滤

consumer.subscribe("topic10", MessageSelector.bySql("age > 16"));

    此时sql过滤遵循SQL92规范

    注意:rocketmq默认是关闭了属性过滤，所以如果需要使用该功能，需要开启enablePropertyFilter的属性，将该属性置为true才可以。

     使用示例:

  producer

public class SyncProducer {

    public static void main(String[] args) throws Exception{
        //Instantiate with a producer group name
        DefaultMQProducer producer = new DefaultMQProducer("producer_group_01");
        //Specify name server addresses
        producer.setNamesrvAddr("localhost:9876");
        //Launch the instance
        producer.start();
        //Create a message instance, specifying topic, tag and message body.
        Message msg = new Message("topic10",
        "TagA",
                ("Hello RocketMQ ").getBytes(RemotingHelper.DEFAULT_CHARSET));
        //set user property
        msg.putUserProperty("name", "zhangsan");
        msg.putUserProperty("age", "18");
        //Call send message to deliver message to one of brokers.
        SendResult sendResult = producer.send(msg);
        System.out.printf("%s%n", sendResult);
        //Shut down once the producer instance is not longer in use.
        producer.shutdown();

    }
}

  consumer

public class Consumer {

    public static void main(String[] args) throws Exception{
        //Instantiate with specified consumer group name.
        DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("consumer_group_01");
        //Specify name server addresses.
        consumer.setNamesrvAddr("localhost:9876");

        //Subscribe one more more topics to consume.
//        consumer.subscribe("topic10", "*");
        consumer.subscribe("topic10", MessageSelector.bySql("age > 16"));

        //Register callback to execute on arrival of messages fetched from brokers.
        consumer.registerMessageListener(new MessageListenerConcurrently() {
            @Override
            public ConsumeConcurrentlyStatus consumeMessage(List list, ConsumeConcurrentlyContext consumeConcurrentlyContext) {
                System.out.printf("%s Receive New Messages: %s %n", Thread.currentThread().getName(), list);
                return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
            }
        });

        //Launch the consumer instance.
        consumer.start();

        System.out.printf("Consumer Started. %n");

    }
}