java – 如何从Activemq异步拉取消息
作者:互联网
我想编写用于从Activemq中提取消息的代码.我不想一次从Activemq中提取所有消息,因为我的要求是每当我的Java应用程序从Activemq收到1条消息时,基于消息体我将找到相应的HTTP链接并转发到该链接.对于这整个逻辑,我写了2个.java文件名
MessageConsumer.java
MyListener.java
MessageConsumer.java文件仅用于连接建立.相应的代码如下.
package PackageName;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.jms.*;
import org.apache.activemq.ActiveMQConnectionFactory;
public class MessageConsumer extends HttpServlet {
@Override
protected void service(HttpServletRequest arg0, HttpServletResponse arg1)
throws ServletException, IOException {
try {
//creating connectionfactory object for way
ConnectionFactory connectionFactory=new
ActiveMQConnectionFactory("admin","admin","tcp://localhost:61617");
//establishing the connection b/w this Application and Activemq
Connection connection=connectionFactory.createConnection();
Session session=connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
Queue queue=session.createQueue("MessageTesing");
javax.jms.MessageConsumer consumer=session.createConsumer(queue);
//fetching queues from Activemq
MessageListener listener = new MyListener();
consumer.setMessageListener(listener);
connection.start();
System.out.println("Press a key to terminate");
}
catch (Exception e) {
// TODO: handle exception
}
}
}
MyListener.java文件用于触发相应的Applications.code,如下所示
package PackageName;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageListener;
import javax.jms.TextMessage;
public class MyListener implements MessageListener {
public void onMessage(Message msg) {
try {
TextMessage msg1=(TextMessage)msg;
//just for your understanding I mention dummy code
System.out.println(msg1.getText());
if (msg1.getText()=="Google") {
System.out.println("Forwarding http link to Google");
}
else {
System.out.println("Forwarding http link to Facebook");
}
} catch (JMSException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
在我的帖子中,我正在触发Google和Facebook链接.但是就我的要求而言,我将调用我自己的Applications.each应用程序花费超过20分钟.所以我想逐个拉消息.之前的消息处理完成然后只有它将收到来自Activemq的另一条消息.
但是知道我一次收到所有的消息.我怎么能解决这个问题.我看过Activemq-Hellowworld计划.我不明白.
对不起,我是Java技术的新手.任何人都可以帮助我.
谢谢.
解决方法:
如果您正在使用MessageListener,那么您实际上是异步接收消息(在另一个线程中).
您可能正在寻找同步消息接收,因此请在主线程中尝试:
final QueueReceiver queueReceiver = queueSession.createReceiver(queue);
queueConnection.start();
while (true) {
Message message = queueReceiver.receive();
// Process your message: insert the code from MyListener.onMessage here
// Possibly add an explit message.acknowledge() here,
// if you want to make sure that in case of an exception no message is lost
// (requires Session.CLIENT_ACKNOWLEDGE, when you create the queue session)
// Possibly terminate program, if a certain condition/situation arises
}
没有MessageListener.
receive()阻塞直到消息可用,因此您的主线程(以及您的程序)在receive方法中等待.如果消息到达,它将接收并处理它.
更新
如果你使用
Session session = connection.createSession(false, Session.CLIENT_ACKNOWLEDGE);
那你应该打电话
message.acknowledge()
消息完全处理完毕后.
而在Session.AUTO_ACKNOWLEDGE的情况下,消息立即从队列中删除(因此如果程序终止处理消息,则丢失).
标签:java,jms,activemq,java-ee-6 来源: https://codeday.me/bug/20190831/1777183.html