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< title > ActiveMQ Management Notification Example< / title >
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< h1 > Management Notification Example< / h1 >
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< p > This example shows how to receive management notifications from ActiveMQ using JMS Messages.< / p >
< p > ActiveMQ servers emit management notifications when events of interest occur (consumers are created or closed,
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destinations are created or deleted, security authentication fails, etc.).< br / >
These notifications can be received either by using JMX (see < a href = "../jmx/readme.html" > JMX example< / a > ) or by receiving JMS Messages
from a well-known destination.< / p >
< p > This example will setup a JMS MessageListener to receive management notifications. We will also perform normal JMS operations to see the kind
of notifications they trigger.< / p >
< h2 > Example configuration< / h2 >
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< p > ActiveMQ can configured to send JMS messages when management notifications are emitted on the server.< / p >
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< p > By default, the management name is called < code > activemq.notifications< / code > but this can be configured in < a href = "server0/activemq-configuration.xml" > activemq-configuration.xml< / a > .
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For this example, we will set it to < code > jms.topic.notificationsTopic< / code > to be able to receive notifications from a JMS Topic.< / p >
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< code > < management-notification-address> jms.topic.notificationsTopic< /management-notification-address> < / code >
< / pre >
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< p > Since we want to lookup the notifications topic using JNDI, we also declare it in < a href = "server0/activemq-jms.xml" > activemq-jms.xml< / a >
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< code > < topic name="notificationsTopic">
< entry name="/topic/notificationsTopic"/>
< /topic> < / code >
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< p > The notification queue requires permission to create/delete temporary queues and consume messages.
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This is also configured in < a href = "server0/activemq-configuration.xml" > activemq-configuration.xml< / a > < / p >
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< code > <!-- security for notification topic -->
< security-setting match="jms.topic.notificationsTopic">
< permission type="consume" roles="guest"/>
< permission type="createNonDurableQueue" roles="guest"/>
< permission type="deleteNonDurableQueue" roles="guest"/>
< /security-setting> < / code >
< / pre >
< h2 > Example step-by-step< / h2 >
< p > < em > To run the example, simply type < code > mvn verify< / code > from this directory< / em > < / p >
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< li > First we need to get an initial context so we can look-up the JMS connection factory and destination objects from JNDI. This initial context will get its properties from < a href = "server0/client-jndi.properties" > client-jndi.properties< / a > < / li >
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< code > InitialContext initialContext = getContext(0);< / code >
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< li > We look up the JMS queue object from JNDI< / li >
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< code > Queue queue = (Queue) initialContext.lookup("/queue/exampleQueue");< / code >
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< li > We look up the JMS connection factory object from JNDI< / li >
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< code > ConnectionFactory cf = (ConnectionFactory) initialContext.lookup("/ConnectionFactory");< / code >
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< li > We create a JMS connection, a session and a message producer for the example queue< / li >
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< code > connection = cf.createConnection();
Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
MessageProducer producer = session.createProducer(queue);< / code >
< / pre >
< li > We look up the JMS Topic used to receive the notifications from JNDI< / li >
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< code > Topic notificationsTopic = (Topic) initialContext.lookup("/topic/notificationsTopic");< / code >
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< li > We create a MessageConsumer for the notification queue and set its MessageListener. When a notification is received, we will simply display all the message properties< / li >
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< code > MessageConsumer notificationConsumer = session.createConsumer(notificationsTopic);
notificationConsumer.setMessageListener(new MessageListener()
{
public void onMessage(Message notif)
{
System.out.println("------------------------");
System.out.println("Received notification:");
try
{
Enumeration propertyNames = notif.getPropertyNames();
while (propertyNames.hasMoreElements())
{
String propertyName = (String)propertyNames.nextElement();
System.out.format(" %s: %s\n", propertyName, notif.getObjectProperty(propertyName));
}
}
catch (JMSException e)
{
}
System.out.println("------------------------");
}
});< / code >
< / pre >
< li > We start the connection to receive messages< / li >
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< code > connection.start();< / code >
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< p > < em > Now that a message listener is setup to receive management notifications, we will perform regular JMS operations to
see what kind of notifications are triggered< / em > < / p >
< li > We create a JMS message consumer on the example queue< / li >
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< code > MessageConsumer consumer = session.createConsumer(queue);< / code >
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< p > This will generate a < code > CONSUMER_CREATED< / code > notification:
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< code > ------------------------
Received notification:
_HQ_RoutingName: jms.queue.exampleQueue
_HQ_Address: jms.queue.exampleQueue
...
_HQ_ConsumerCount: 1
...
_HQ_NotifType: CONSUMER_CREATED
------------------------< / code >
< / pre >
< p > The notification tells us that a consumer was created for the JMS queue < code > exampleQueue< / code > . When the notification
was emitted, this consumer was the only one for the queue< / p >
< li > We close this consumer< / li >
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< code > consumer.close();< / code >
< / pre >
< p > This will generate a < code > CONSUMER_CLOSED< / code > notification:
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< code > ------------------------
Received notification:
_HQ_RoutingName: jms.queue.exampleQueue
_HQ_Address: jms.queue.exampleQueue
...
_HQ_ConsumerCount: 0
...
_HQ_NotifType: CONSUMER_CLOSED
------------------------< / code >
< / pre >
< p > The notification tells us that a consumer was closed for the JMS queue < code > exampleQueue< / code > . When the notification
was emitted, there were no other consumers on the queue< / p >
< li > As a last example, we will create a connection with invalid user credentials< / li >
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< code > try
{
cf.createConnection("not.a.valid.user", "not.a.valid.password");
} catch (JMSException e)
{
}< / code >
< / pre >
< p > This will generate a < code > SECURITY_AUTHENTICATION_VIOLATION< / code > notification:
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< code > ------------------------
Received notification:
_HQ_User: not.a.valid.user
...
_HQ_NotifType: SECURITY_AUTHENTICATION_VIOLATION
------------------------
< / code >
< / pre >
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< p > The notification tells us that a user named < code > not.a.valid.user< / code > failed to authenticate when creating a connection to ActiveMQ.< / p >
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< li > And finally, < b > always< / b > remember to close your JMS connections and resources after use, in a < code > finally< / code > block. Closing a JMS connection will automatically close all of its sessions, consumers, producer and browser objects< / li >
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< code > finally
{
if (initialContext != null)
{
initialContext.close();
}
if (connection != null)
{
connection.close();
}
}< / code >
< / pre >
< / ol >
< h2 > More information< / h2 >
< ul >
< li > User Manual's < a href = "../../../docs/user-manual/en/html_single/index.html#management.notifications" > Management Notifications chapter< / a > < / li >
< / ul >
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