rocketmq(三 java操作rocket API, rocketmq 幂等性)
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- JAVA操作rocketmq：
1.导入rocketmq所需要的依赖：
<
dependency
>
<
groupId
>com.alibaba.rocketmq</groupId><artifactId>rocketmq-client</artifactId><version>3.0.10</version></dependency><dependency><groupId>com.alibaba.rocketmq</groupId><artifactId>rocketmq-all</artifactId><version>3.0.10</version><type>pom</type></dependency>
2.创建生产者
package
com.example.producer;
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 {
DefaultMQProducer producer = new DefaultMQProducer("producer-group");
producer.setNamesrvAddr("192.168.31.165:9876;192.168.31.144:9876");
producer.setInstanceName("producer");
producer.start();
try {
for (int i = 0; i < 10; i++) {
// Thread.sleep(1000); // 每秒发送一次MQ
Message msg = new Message("producer-topic", // topic 主题名称
"msg", // pull 临时值 在消费者消费的时候 可以根据msg类型进行消费
("pushmsg-" + i).getBytes()// body 内容 );
SendResult sendResult = producer.send(msg);
System.out.println(sendResult.toString());
}
} catch (Exception e) {
e.printStackTrace();
}
producer.shutdown();
}
}
3.创建消费者
package
com.example.consumer;
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.message.MessageExt;
public
class
Consumer {
public
static
void main(String[] args) throws MQClientException {
DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("consumer-group");
consumer.setNamesrvAddr("192.168.31.165:9876;192.168.31.144:9876");
consumer.setInstanceName("consumer");
consumer.subscribe("producer-topic", "msg");//此处是根据Message对象的参数来获取
consumer.registerMessageListener(new MessageListenerConcurrently() {
@Override
public ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs, ConsumeConcurrentlyContext context) {
for (MessageExt msg : msgs) {
System.out.println("消息id:"+msg.getMsgId() + "---" + new String(msg.getBody()));
}
return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
}
});
consumer.start();
}
}
4.运行结果：
生产者运行结果：
消费者运行结果：
- rocetmq幂等性问题：
在Activemq中 jms规范支持两种消息模型：点对点和发布订阅，在rocketmq中 有两种消费模式：广播消费,和集群消费。
在消费的过程中，如果消费者出现异常或者超时，导致mq没有及时的相应消费的状态，则可能让mq重试，重试机制就有可能导致出现幂等性，而rocketmq的幂等性 只会出现在集群消费(类似activemq中的点对点消息模型)
生产者：
package
com.example.producer;
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 {
DefaultMQProducer producer = new DefaultMQProducer("producer-group");
producer.setNamesrvAddr("192.168.31.169:9876;192.168.31.177:9876");
producer.setInstanceName("producer");
producer.start();
try {
for (int i = 0; i < 10; i++) {
Message msg = new Message("topic", // topic 主题名称
"msg", // pull 临时值 在消费者消费的时候 可以根据msg类型进行消费
(i + "条消息").getBytes()// body 内容 );
SendResult sendResult = producer.send(msg);
System.out.println(sendResult.toString());
}
} catch (Exception e) {
e.printStackTrace();
}
producer.shutdown();
}
}
消费者：
package
com.example.consumer;
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.message.MessageExt;
public
class
Consumer {
public
static
void main(String[] args) throws MQClientException {
DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("consumer-group");
consumer.setNamesrvAddr("192.168.31.169:9876;192.168.31.177:9876");
consumer.setInstanceName("consumer");
consumer.subscribe("topic1", "msg");
consumer.registerMessageListener(new MessageListenerConcurrently() {
@Override
public ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs, ConsumeConcurrentlyContext context) {
for (MessageExt msg : msgs) {
System.out.println("消息id:" + msg.getMsgId() + "---" + new String(msg.getBody()));
}
// 超时的情况 或者程序异常int i = 2 / 0;
return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
}
});
consumer.start();
}
}
消费结果：
消息id:C0A81FB100002A9F00000000000268EC---5条消息 消息id:C0A81FB100002A9F000000000002686E---4条消息 消息id:C0A81FA900002A9F0000000000037E6A---1条消息 消息id:C0A81FB100002A9F000000000002696A---6条消息 消息id:C0A81FB100002A9F00000000000269E8---7条消息 消息id:C0A81FA900002A9F0000000000038062---9条消息 消息id:C0A81FA900002A9F0000000000037EE8---2条消息 消息id:C0A81FA900002A9F0000000000037FE4---8条消息 消息id:C0A81FA900002A9F0000000000037F66---3条消息 消息id:C0A81FA900002A9F0000000000037DEC---0条消息 消息id:C0A81FA900002A9F0000000000038704---1条消息 消息id:C0A81FA900002A9F000000000003880C---9条消息 消息id:C0A81FA900002A9F0000000000038914---2条消息 消息id:C0A81FA900002A9F0000000000038A1C---0条消息 消息id:C0A81FA900002A9F0000000000038B24---3条消息 消息id:C0A81FA900002A9F0000000000038C2C---8条消息 消息id:C0A81FB100002A9F0000000000026E7E---4条消息 消息id:C0A81FB100002A9F0000000000026F86---7条消息 消息id:C0A81FB100002A9F0000000000027196---5条消息 消息id:C0A81FB100002A9F000000000002708E---6条消息
在Activimq中,可以通过消息id 来作为全局变量，检测是不是重复消费。但是在rocketmq中消费重试的结果中，任意选出两条相同的消息，可以看出 重试的时候消息id是不同的，此时在用消息id作为全局变量判断是否重复消费显然是不可能的。rocketmq中提供了一个消息的key，可以将业务id作为该key。例如：订单号什么的。可以将消息设置的key 在第一次消费的时候存放到数据库之中
幂等性消费者：
package
com.example.consumer;
import
java.util.HashMap;
import
java.util.List;
import
java.util.Map;
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.message.MessageExt;
public
class
Consumer {
public
static Map<String, String> map = new HashMap<String, String>();// 模拟内存，实际情况可以将key放在redis之中publicstaticvoid main(String[] args) throws MQClientException {
DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("consumer-group");
consumer.setNamesrvAddr("192.168.31.169:9876;192.168.31.177:9876");
consumer.setInstanceName("consumer");
consumer.subscribe("topic1", "msg");
consumer.registerMessageListener(new MessageListenerConcurrently() {
@Override
public ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs, ConsumeConcurrentlyContext context) {
for (MessageExt msg : msgs) {
if (!map.containsKey(msg.getKeys())) {
// 如果此时的业务逻辑是将收到的消息存放到数据库
System.out.println("消息id:" + msg.getMsgId() + "---" + new String(msg.getBody()));
map.put(msg.getKeys(), new String(msg.getBody()));
} else {
System.out.println("重复消费");
return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
}
}
// 超时的情况 或者程序异常int i = 2 / 0;
return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
}
});
consumer.start();
}
}
原文：https://www.cnblogs.com/920913cheng/p/10730497.html
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