A Destination List Metrics Example
The source file for this code example is DestListMetrics.java. This client application monitors the list of destinations on a broker by subscribing to the topic mq.metrics.destination_list. The messages that arrive contain information describing the destinations that currently exist on the broker, such as destination name, destination type, and whether the destination is temporary.
Example 4–3 shows how to subscribe to mq.metrics.destination_list.
Example 4–3 Example of Subscribing to the Destination List Metrics Topic
com.sun.messaging.TopicConnectionFactory metricConnectionFactory;
TopicConnection metricConnection;
TopicSession metricSession;
TopicSubscriber metricSubscriber;
Topic metricTopic;
String metricTopicName = null;
metricConnectionFactory = new com.sun.messaging.TopicConnectionFactory();
metricConnection = metricConnectionFactory.createTopicConnection();
metricConnection.start();
metricSession = metricConnection.createTopicSession(false,
Session.AUTO_ACKNOWLEDGE);
metricTopicName = "mq.metrics.destination_list";
metricTopic = metricSession.createTopic(metricTopicName);
metricSubscriber = metricSession.createSubscriber(metricTopic);
metricSubscriber.setMessageListener(this);
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The incoming message is processed in the onMessage() method, as shown in Example 4–4:
Example 4–4 Example of Processing a Destination List Metrics Message
public void onMessage(Message m) {
try{
MapMessage mapMsg = (MapMessage)m;
String type = mapMsg.getStringProperty("type");
if (type.equals(metricTopicName)) {
String oneRow[] = new String[ 3 ];
/*
* Extract metrics
*/
for (Enumeration e = mapMsg.getMapNames();
e.hasMoreElements();) {
String metricDestName = (String)e.nextElement();
Hashtable destValues =
(Hashtable)mapMsg.getObject(metricDestName);
int i = 0;
oneRow[i++] = (destValues.get("name")).toString();
oneRow[i++] = (destValues.get("type")).toString();
oneRow[i++] = (destValues.get("isTemporary")).toString();
mp.add(oneRow);
}
mp.print();
System.out.println("");
mp.clear();
} else {
System.err.println("Msg received:
not destination list metric type");
}
} catch (Exception e) {
System.err.println("onMessage: Exception caught: " + e);
}
}
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Notice how the metrics type is extracted and checked, and how the list of destinations is extracted. By iterating through the map names in mapMsg and extracting the corresponding value (a hashtable), you can construct a list of all the destinations and their related information.
As discussed in Format of Metrics Messages, these map names are metrics topic names having one of two forms:
mq.metrics.destination.queue.monitored_destination_name mq.metrics.destination.topic.monitored_destination_name
(The map names can also be used to monitor a destination, but that is not done in this particular example.)
Notice that from each extracted hashtable, the information on each destination is extracted using the keys name, type, and isTemporary. The extraction code from the previous code example is reiterated here for your convenience.
Example 4–5 Example of Extracting Destination Information From a Hash Table
String metricDestName = (String)e.nextElement();
Hashtable destValues = (Hashtable)mapMsg.getObject(metricDestName);
int i = 0;
oneRow[i++] = (destValues.get("name")).toString();
oneRow[i++] = (destValues.get("type")).toString();
oneRow[i++] = (destValues.get("isTemporary")).toString();
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Run this example monitoring client with the following command:
java DestListMetrics
The output looks like the following:
--------------------------------------------------- Destination Name Type IsTemporary --------------------------------------------------- SimpleQueue queue false fooQueue queue false topic1 topic false |
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