16 MXBeans
This example demonstrates the use of MXBeans. The source code contained in this
section is used to create corresponding files in the
examples/
directory specified in
the appropriate setup procedure and includes:
-
README file
-
Main
-
QueueSample
-
QueueSampler
-
QueueSamplerMXBean
examples/MXBean/README
# ==============================================================================
#
# JMX Tutorial Introductory Example : Instrumenting Your Own Applications.
# Using MXBeans.
#
# The aim of this introductory example is to show the basic features of
# the JMX technology first by instrumenting a simple resource using the new
# type of MBean, i.e. MXBeans, and second by performing operations on it using
# the jconsole tool. This example shows the implementation of an MXBean, how to
# register it in the Platform MBean Server and how to perform remote operations
# on it by connecting to the RMI connector server using the jconsole tool. The
# goal of this example is to show a simple MXBean that manages a resource of
# type Queue<String>. The MXBean declares a getter getQueueSample that takes
# a snapshot of the queue when invoked and returns a Java class QueueSample
# that bundles the following values together: the time the snapshot was taken,
# the queue size and the head of the queue at that given time. The MXBean also
# declares an operation clearQueue that clears all the elements in the queue
# being managed. The example also shows how to register this MXBean in the
# Platform MBean Server alongside the MBeans you can already see in jconsole.
# This examples also shows how the existing Platform MBean Server can be
# shared between the JVM and the application itself to register the application
# MBeans, thus avoiding the creation of multiple MBean Server instances on the
# same JVM.
#
# ==============================================================================
#
# In order to compile and run the example, make a copy of this README file, and
# then simply cut and paste all the commands as needed into a terminal window.
#
# This README makes the assumption that you are running under Java SE 6 on Unix,
# you are familiar with the JMX technology, and with the bourne shell or korn
# shell syntax.
#
# All the commands below are defined using Unix korn shell syntax.
#
# If you are not running Unix and korn shell you are expected to be able to
# adapt these commands to your favorite OS and shell environment.
#
# Compile Java classes
#
# The Java classes used in this example are contained in the com.example.mxbeans
# Java package.
#
# * Main.java: gets the Platform MBean Server, and creates
# and registers the QueueSampler MXBean on it.
#
# * QueueSampler.java: implements the QueueSampler MXBean.
#
# * QueueSamplerMXBean.java: the management interface exposed
# by the QueueSampler MXBean.
#
# * QueueSample.java: the Java type returned by the getQueueSample()
# method in the QueueSampler MXBean interface.
#
javac com/example/mxbeans/*.java
# Start the Main application
#
java com.example.mxbeans.Main
# Start jconsole on a different shell window on the same machine
#
# JConsole is located in $(J2SE_HOME)/bin/jconsole
#
jconsole
# ==============================================================================
examples/MXBean/com/example/mxbeans/Main.java
/**
* Main.java - main class for QueueSampler example. Create the Queue Sampler
* MXBean, register it, then wait forever (or until the program is interrupted).
*/
package com.example.mxbeans;
import java.lang.management.ManagementFactory;
import java.util.Queue;
import java.util.concurrent.ArrayBlockingQueue;
import javax.management.MBeanServer;
import javax.management.ObjectName;
public class Main {
/* For simplicity, we declare "throws Exception". Real programs
will usually want finer-grained exception handling. */
public static void main(String[] args) throws Exception {
// Get the Platform MBean Server
MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
// Construct the ObjectName for the MBean we will register
ObjectName name =
new ObjectName("com.example.mxbeans:type=QueueSampler");
// Create the Queue Sampler MXBean
Queue<String> queue = new ArrayBlockingQueue<String>(10);
queue.add("Request-1");
queue.add("Request-2");
queue.add("Request-3");
QueueSampler mxbean = new QueueSampler(queue);
// Register the Queue Sampler MXBean
mbs.registerMBean(mxbean, name);
// Wait forever
System.out.println("Waiting...");
Thread.sleep(Long.MAX_VALUE);
}
}
examples/MXBean/com/example/mxbeans/QueueSamplerMXBean.java
/**
* QueueSamplerMXBean.java - MXBean interface describing the management
* operations and attributes for the QueueSampler MXBean. In this case
* there is a read-only attribute "QueueSample" and an operation "clearQueue".
*/
package com.example.mxbeans;
public interface QueueSamplerMXBean {
public QueueSample getQueueSample();
public void clearQueue();
}
examples/MXBean/com/example/mxbeans/QueueSampler.java
/**
* QueueSampler.java - MXBean implementation for the QueueSampler MXBean.
* This class must implement all the Java methods declared in the
* QueueSamplerMXBean interface, with the appropriate behavior for each one.
*/
package com.example.mxbeans;
import java.util.Date;
import java.util.Queue;
public class QueueSampler implements QueueSamplerMXBean {
private Queue<String> queue;
public QueueSampler(Queue<String> queue) {
this.queue = queue;
}
public QueueSample getQueueSample() {
synchronized (queue) {
return new QueueSample(new Date(), queue.size(), queue.peek());
}
}
public void clearQueue() {
synchronized (queue) {
queue.clear();
}
}
}
examples/MXBean/com/example/mxbeans/QueueSample.java
/**
* QueueSample.java - Java type representing a snapshot of a given queue.
* It bundles together the instant time the snapshot was taken, the queue
* size and the queue head.
*/
package com.example.mxbeans;
import java.beans.ConstructorProperties;
import java.util.Date;
public class QueueSample {
private final Date date;
private final int size;
private final String head;
@ConstructorProperties({"date", "size", "head"})
public QueueSample(Date date, int size, String head) {
this.date = date;
this.size = size;
this.head = head;
}
public Date getDate() {
return date;
}
public int getSize() {
return size;
}
public String getHead() {
return head;
}
}