Embedding ActiveMQ into Tomcat: three important knowledge points need to be mastered

ActiveMQ embedded in Tomcat

In some projects, opening an ActiveMQ separately is sometimes a bit cumbersome for project implementation. So we embed ActiveMQ into Tomcat, and ActiveMQ is started at the same time that Tomcat starts. From this we need to master three important knowledge points

• BrokerService in ActiveMQ

• Auto-start Servlet configuration

• Use jconsole to understand the running status of embedded ActiveMQ

1. Enable BrokerService

Add ActiveMQ dependency in pom.xml. This code example uses version 5.7 ,Remember that onlyactivemq-coreis enough.

 org.apache.activemq activemq-core 5.7.0 

When writing theBrokerServicecode part, pay attention to three main points

1. Whether monitoring information needs to be displayed injconsolebroker.setUseJmx(true)

2. Set the connection username and password, how to use the verification plug-in

3. Whether it is persistent, Storage location settings, persistence configuration

So you need to start a connection addresstcp://localhost:61616, the user name isadmin, The password isadmin, which needs to be persisted. The storage address of the persistent data file is/activemq. The code of the BrokerService that needs to be started byjconsoleis as follows:

// author:herbert qq:464884492 BrokerService broker = new BrokerService(); broker.setUseJmx(true); // 开启监控 broker.setPersistent(true); // 持久化 broker.setBrokerName("Test"); SimpleAuthenticationPlugin sap = new SimpleAuthenticationPlugin(); AuthenticationUser au = new AuthenticationUser("admin", "admin","users"); ArrayList d = new ArrayList(); d.add(au); sap.setUsers(d); // 用户验证 broker.setPlugins(new BrokerPlugin[] { sap }); String mqDataPath = "/activemq"; // 存储位置 broker.getPersistenceAdapter().setDirectory(new File(mqDataPath)); broker.addConnector("tcp://localhost:61616"); // 连接地址 broker.start();

2. Producers and consumers

In ActiveMQ, there are two general message delivery methods

• queue, which supports message persistence and unconsumed messages , persists after reboot. If there are multiple consumers, on the premise of extracting one message at a time, all consumers will share the message

• topics in the queue equally. Message persistence is not supported. Unconsumed messages will be Messages are lost after reboot. If there are multiple consumers, each consumer consumes all the messages in the topic in turn

Whether it is written by the producer or the consumer code, there are mainly4steps

1. Establish a connection, usefailover:()method, automatically disconnect and reconnect

2. EstablishSession, get the sending or receiving destinationDestination, specify whether it is a queue (session.createQueue(queueName)) or a topic (session.createTopic(topicName))

3. Get the producer or consumer throughSession

4. Produce or consume messages

We now write a producer code and loop to generate 10 messages

// author:herbert qq:464884492 String mqConnUrl = "tcp://localhost:61616"; String connUrl = "failover:(" + mqConnUrl.trim()+ ")?initialReconnectDelay=1000&maxReconnectDelay=30000"; ConnectionFactory connectionFactory = new ActiveMQConnectionFactory("admin","admin", connUrl); javax.jms.Connection connection = connectionFactory.createConnection(); connection.start(); Session session = connection.createSession(false,Session.AUTO_ACKNOWLEDGE); Destination destination = session.createQueue("system"); MessageProducer messageProducer = session.createProducer(destination); for (int i = 0; i < 10; i++) { javax.jms.TextMessage message = session.createTextMessage("ActiveMQ 发送的消息" + i); System.out.println("发送消息：" + "ActiveMQ 发送的消息" + i); messageProducer.send(message); }

Write a consumer to consume the above 10 messages

// author:herbert qq:464884492 String mqConnUrl = "tcp://localhost:61616"; String connUrl = "failover:(" + mqConnUrl.trim()+ ")?initialReconnectDelay=1000&maxReconnectDelay=30000"; ConnectionFactory connectionFactory = new ActiveMQConnectionFactory("admin", "admin", connUrl); javax.jms.Connection connection = connectionFactory.createConnection(); connection.start(); Session session = connection.createSession(false,Session.AUTO_ACKNOWLEDGE); Destination destination = session.createQueue("system"); MessageConsumer messageConsumer = session.createConsumer(destination); messageConsumer.setMessageListener(new MessageListener() { @Override public void onMessage(javax.jms.Message message) { ActiveMQTextMessage m = (ActiveMQTextMessage) message; try { System.out.println("接收到：" + m.getText()); } catch (JMSException e) { e.printStackTrace(); } } });

Operation effect

It can be seen that the 10 messages generated by our producer have been successfully processed by the consumer.

3. Monitor embedded ActiveMQ

For embedded ActiveMQ, you need to set broker.setUseJmx(true) before starting BrokerService; then find your JAVA_HOME, switch to bin, and enter the jconsole command.

#After jconsole starts, select the process where ActiveMQ is located. After connecting, select the Mbean tab

. The red boxes indicate the number of messages that have been consumed and those that have entered MQ. Select the operation, find the SendTextMessage, and you can also send messages to this queue.

4. Selvelt starts with Tomcat

For Tomcat after Tomcat7.This value>=0 indicates that self-starting is required. The smaller the value, the higher the priority.

// author:herbert qq:464884492 @WebServlet(urlPatterns = "/initmq", loadOnStartup = 1) public class InitMqServlet extends HttpServlet { @Override public void init(ServletConfig config) throws ServletException { super.init(config); // 这里编写启动ActiveMQ代码 } }

activemq-broker, resulting in messages being able to be connected but not being sent. Afterwards, directly replace it withactivemq-all. If there is a slf4j log conflict, usingexclusionsstill cannot solve the problem. In the end, we only rely onactivemq-core, which perfectly solves all problems.

JMS message persistence, persist ActiveMQ messages to mySql database

Related understanding of Session settings in ActiveMQ

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