RocketMQ使用Filter问题！

OK,我们在使用RocketMQ的Filter服务时候，需要注意一些问题，如题我们迅速开始吧！

首先，我们需要启动我们的MQ服务，顺序为 namesrv、broker、filter。我配置的为：2m-2s-async（也就是两主两从模式）

我们需要在broker-*.properties文件里添加一句话，如下：

filterServerNums=1

其实我们也可以手工的去启动filter！

接下来：

马上进行建立rocketMQAPI工程，然后引入jar，可从github上来下载demo，地址为：https://github.com/alibaba/RocketMQ ，如图所示：

首先看一下product端代码，如下：发送100条消息到broker。

package bhz.mq.filter;

import com.alibaba.rocketmq.client.exception.MQClientException;
import com.alibaba.rocketmq.client.producer.DefaultMQProducer;
import com.alibaba.rocketmq.client.producer.SendResult;
import com.alibaba.rocketmq.common.message.Message;
 
 
public class Producer {
    public static void main(String[] args) throws MQClientException, InterruptedException {
        String group_name = "filter_producer";
        DefaultMQProducer producer = new DefaultMQProducer(group_name);
        producer.setNamesrvAddr("192.168.1.111:9876;192.168.1.112:9876;192.168.1.113:9876;192.168.1.114:9876");
        producer.start();
        try {
            for (int i = 0; i < 100; i++) {
                Message msg = new Message("TopicFilter7",// topic
                    "TagA",// tag
                    "OrderID001",// key
                    ("Hello MetaQ" + i).getBytes());// body
                msg.putUserProperty("SequenceId", String.valueOf(i));
                SendResult sendResult = producer.send(msg);
                System.out.println(sendResult);
            }
        }
        catch (Exception e) {
            e.printStackTrace();
        }
        producer.shutdown();
    }
}

接下来我们看一下consumer代码，如下：需要注意的一点是我们所上传的过滤器类里，一定不允许有中文，否则MixAll.file2String方法返回null，Filter不识别！！！！

package bhz.mq.filter;

import java.io.UnsupportedEncodingException;
import java.util.List;

import com.alibaba.rocketmq.client.consumer.DefaultMQPushConsumer;
import com.alibaba.rocketmq.client.consumer.listener.ConsumeConcurrentlyContext;
import com.alibaba.rocketmq.client.consumer.listener.ConsumeConcurrentlyStatus;
import com.alibaba.rocketmq.client.consumer.listener.MessageListenerConcurrently;
import com.alibaba.rocketmq.client.exception.MQClientException;
import com.alibaba.rocketmq.common.MixAll;
import com.alibaba.rocketmq.common.consumer.ConsumeFromWhere;
import com.alibaba.rocketmq.common.message.MessageExt;
 
 
public class Consumer {
 
    public static void main(String[] args) throws InterruptedException, MQClientException {
        String group_name = "filter_consumer";
        DefaultMQPushConsumer consumer = new DefaultMQPushConsumer(group_name);
        consumer.setNamesrvAddr("192.168.1.111:9876;192.168.1.112:9876;192.168.1.113:9876;192.168.1.114:9876");
        // 使用Java代码，在服务器做消息过滤
        String filterCode = MixAll.file2String("D:\\workspace_001\\rocketmqAPI\\src\\bhz\\mq\\filter\\MessageFilterImpl.java");
        System.out.println(filterCode);
        consumer.subscribe("TopicFilter7", "bhz.mq.filter.MessageFilterImpl", filterCode);
        consumer.registerMessageListener(new MessageListenerConcurrently() {
            @Override
            public ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs,
                    ConsumeConcurrentlyContext context) {
                //System.out.println(Thread.currentThread().getName() + " Receive New Messages: " + msgs);
                try {
                    System.out.println(new String(msgs.get(0).getBody(),"utf-8"));
                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                }
                return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
            }
        });
        consumer.start();
        System.out.println("Consumer Started.");
   }
}

OK 最后我们看一下MessageFilterImpl这个类：再次强调一下，注意这个类是上传到FilterSrv的，不要有中文，上面说了不然MixAll.file2String方法返回null。

package bhz.mq.filter;
import com.alibaba.rocketmq.common.filter.MessageFilter;
import com.alibaba.rocketmq.common.message.MessageExt;
 
 
public class MessageFilterImpl implements MessageFilter {
 
    @Override
    public boolean match(MessageExt msg) {
        // NO Chinese
        System.out.println("-------------");
        String property = msg.getUserProperty("SequenceId");
        System.out.println("---------" + property);
        if (property != null) {
            int id = Integer.parseInt(property);
            if((id % 2) == 0) {
            //if ((id % 3) == 0 && (id > 10)) {
                return true;
            }
        }
 
        return false;
    }
}

OK。我们进行测试，先运行consumer，然后运行producer发送数据，这样就好根据MessageFilterImpl的代码过滤出来 id % 2 == 0 的所有数据给Consumer端消费了！

最后我们总结下：我们一般是一个broker上配置多个filter服务，其实就是用cpu换取宝贵网卡的资源！