The VMMetrics example is a JMS application that monitors the Java VM used by the Sun Java(tm) System Message Queue broker
/*
* @(#)VMMetrics.java 1.3 04/01/05
*
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import java.util.Enumeration;
import java.util.Properties;
import javax.jms.*;
/**
* The VMMetrics example is a JMS application that monitors the
* Java VM used by the Sun Java(tm) System Message Queue broker. It does so by
* subscribing to a topic named 'mq.metrics.jvm'. The messages that arrive
* contain Java VM information such as:
* - amount of free memory
* - amount of maximum memory
* - total amount of memory
*
* By default VMMetrics will connect to the broker running on localhost:7676.
* You can use -DimqAddressList attribute to change the host, port and
* transport:
*
* java -DimqAddressList=mq://<host>:<port>/jms VMMetrics
*/
public class VMMetrics implements MessageListener {
ConnectionFactory metricConnectionFactory;
Connection metricConnection;
Session metricSession;
MessageConsumer metricConsumer;
Topic metricTopic;
MetricsPrinter mp;
int rowsPrinted = 0;
public static void main(String args[]) {
VMMetrics bm = new VMMetrics();
bm.initPrinter();
bm.initJMS();
bm.subscribeToMetric();
}
/*
* Initializes the class that does the printing, MetricsPrinter.
* See the MetricsPrinter class for details.
*/
private void initPrinter() {
String oneRow[] = new String[ 3 ];
int i = 0;
mp = new MetricsPrinter(3, 2, "-");
i = 0;
oneRow[i++] = "Free Memory";
oneRow[i++] = "Max Memory";
oneRow[i++] = "Total Memory";
mp.addTitle(oneRow);
}
/**
* Create the Connection and Session etc.
*/
public void initJMS() {
try {
metricConnectionFactory = new com.sun.messaging.ConnectionFactory();
metricConnection = metricConnectionFactory.createConnection();
metricConnection.start();
// creating Session
// Transaction Mode: None
// Acknowledge Mode: Automatic
metricSession = metricConnection.createSession(false,
Session.AUTO_ACKNOWLEDGE);
} catch(Exception e) {
System.err.println("Cannot create metric connection or session: "
+ e.getMessage());
e.printStackTrace();
System.exit(1);
}
}
public void subscribeToMetric() {
try {
metricTopic = metricSession.createTopic("mq.metrics.jvm");
metricConsumer = metricSession.createConsumer(metricTopic);
metricConsumer.setMessageListener(this);
} catch(JMSException e) {
System.err.println("Cannot subscribe to metric topic: "
+ e.getMessage());
e.printStackTrace();
System.exit(1);
}
}
/*
* When a metric message arrives
* - verify it's type
* - extract it's fields
* - print one row of output
*/
public void onMessage(Message m) {
try {
MapMessage mapMsg = (MapMessage)m;
String type = mapMsg.getStringProperty("type");
if (type.equals("mq.metrics.jvm")) {
String oneRow[] = new String[ 3 ];
int i = 0;
/*
* Extract broke metrics
*/
oneRow[i++] = Long.toString(mapMsg.getLong("freeMemory"));
oneRow[i++] = Long.toString(mapMsg.getLong("maxMemory"));
oneRow[i++] = Long.toString(mapMsg.getLong("totalMemory"));
mp.add(oneRow);
if ((rowsPrinted % 20) == 0) {
mp.print();
} else {
mp.print(false);
}
rowsPrinted++;
mp.clear();
} else {
System.err.println("Msg received: not vm metric type");
}
} catch (Exception e) {
System.err.println("onMessage: Exception caught: " + e);
}
}
}
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