我目前正在为持久订阅编程一个信使服务(它可能最终是不持久的,我们仍在讨论),我正在寻找一些关于如何处理服务器因任何原因暂时关闭,我们需要自动重新订阅该主题的场景的建议。以下是它如何连接的示例代码:
public void DurableChatter(String broker, String username, String password)
{
javax.jms.MessageProducer publisher = null;
javax.jms.MessageConsumer subscriber = null;
javax.jms.Topic topic = null;
//Create a connection:
try{
javax.jms.ConnectionFactory factory;
factory = (new progress.message.jclient.ConnectionFactory (broker));
connection = factory.createConnection (username, password);
//Durable Subscriptions are indexed by username, clientID and subscription name
//It is a good proactice to set the clientID:
connection.setClientID(CLIENT_ID);
pubSession = connection.createSession(false,javax.jms.Session.AUTO_ACKNOWLEDGE);
subSession = connection.createSession(false,javax.jms.Session.AUTO_ACKNOWLEDGE);
}
catch (javax.jms.JMSException jmse){
System.err.println ("Error: Cannot connect to Broker - " + broker);
jmse.printStackTrace();
System.exit(1);
}
//Create Publisher and Durable Subscriber:
try{
topic = pubSession.createTopic(APP_TOPIC);
subscriber = subSession.createDurableSubscriber(topic, "SampleSubscription");
subscriber.setMessageListener(this);
publisher = pubSession.createProducer(topic);
connection.start();
}
catch (javax.jms.JMSException jmse){
System.out.println("Error: connection not started.");
jmse.printStackTrace();
System.exit(1);
}
//Wait for user input
try
{
System.out.println("Enter text to send as message and press enter.");
java.io.BufferedReader stdin =
new java.io.BufferedReader(new java.io.InputStreamReader(System.in));
while (true)
{
String s = stdin.readLine();
if(s == null){
exit();
}
else if (s.length()>0)
{
try
{
javax.jms.TextMessage msg = pubSession.createTextMessage();
msg.setText(username + ": " + s);
//Publish the message persistantly:
publisher.send(
msg, //message
javax.jms.DeliveryMode.PERSISTENT, //publish persistantly
javax.jms.Message.DEFAULT_PRIORITY,//priority
MESSAGE_LIFESPAN); //Time to Live
}
catch (javax.jms.JMSException jmse){
System.err.println("Error publishing message:" + jmse.getMessage());
}
}
}
}
catch (java.io.IOException ioe)
{
ioe.printStackTrace();
}
}
您应该将客户端设为implement javax.jmsExceptionListener
。
这将允许您的客户端在连接丢失时立即接收到来自JMS'API的回调,即使您的应用程序目前没有发布任何内容。
在创建Connection
、连接并启动它之后,调用connection.setExceptionListener(myListener)
。另请参阅连接的Javadoc。
故障检测需要多快?设置您的协议,确保每个客户端每分钟至少发送一条消息(您需要在通信协议中添加一些新的"错误"保活消息)-任何没有收到保活消息的客户端都可以安全地假设服务器已关闭并开始重新连接。
理想情况下,这类事情最好用UDP广播而不是JMS(为了开销)来完成,但我假设如果您有UDP广播作为选项,您会使用jgroups来为您进行集群detecion/ffailure/rejoin。