javatmanagementextensionsjmxt-111224090411-phpapp02

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Java Management Extensions (JMX)

Introduction

Tarun Telang,SAP NetWeaver Life Cycle Management,

May 2008


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1. Overview1.1. Introduction?

1.2. Architecture

1.2. Why JMX?

2. MBeans

2.1. What are MBeans?

2.2. Writing MBeans

3. Agents

3.1. What are Agents?3.2. Registering MBeans

4. Code Snippets

4.1. Connecting to MBean Server

4.2. Accessing MBean

Agenda


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Introduction

Java Management Extensions (JMX) is an open technology specification that defines the

management architecture, which enables management and monitoring of applications andservices.

JMX Architecture provides interfacesfor defining runtime monitoring, managementandconfiguration supportfor applications.

The JMX architecturehas three layers:

Distributed layer - adaptors or connectors

Agent layer - JMX Services and MBean Server

Instrumentation layer - Managed Beans encapsulating the resources

JMX is part of both Java SE and Java EE specifications.


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JMX Architecture

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JVM( host2)

JVM(host1)

Application

MBeans

Instrumentation Layer

Mbean Server

AgentServices

Agent Level

Protocol Adaptersand Connectors

Web Browser

JMX CompliantManagementApplication

JMX Manager

ProprietaryManagementApplication

Distributed Services Level


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Why JMX?

JMX is suitable for:

adapting legacy systems

implementing new solution for management, and monitoring

plugging into future applications.

JMX is usedto provide application management for:

Web applications.

Stand-alone applications.

Application servers.

Services.

Java-enabled devices.

The roleof JMX in J2EE applications is to:

Expose portions of JMS and EJB components to a management console.

Monitor the application server.

Configure the runtime environment for your application.

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MBeans

MBeans are managed Java objects, similar to Java Bean

MBeans represents a resourcethat needs to be managed.

resources are instrumented by MBeans

MBeans exposes management interface.

MBeans must have an object name Getters/Setters for attributes

Management operations

Self description

Object Name Represents an MBean, or a patternthat can match the names of several MBeans.

Syntax: "domain:=

Example: com.example.mbean:key1=value1, key2=value2, ... keyN=valueN

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Writing MBean

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// The Memory MBean Interface

public interfaceMemoryMBean {

// read

public int getUsedMemory();

// write

public voidsetUsedMemory(int size);

// read only

public int getTotalMemory();

// operation

public intcalculateFreeMemory();

}

// Memory MBean Implementation

public classMemory implementsMemoryMBean {

private static final int MEMORY_SIZE = 512;

private int totalMemory = MEMORY_SIZE;

private int usedMemory = 0;

....

public int getUsedMemory() {

return this.usedMemory;

}

public synchronized void setUsedMemory(int size)

{

this.usedMemory = size;

}

public float calculateFreeMemory() {

returntotalMemory - usedMemory;

}

}


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Registering MBean with MBean Server

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import java.lang.management.*;

import javax.management.*;

public class MemoryAgent {

public static void main(String[] args)throws Exception {

MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();

ObjectName name = new ObjectName("com.developersummit.mbeans:type=Memory");

MemoryMBean mbean = newMemory();

mbs.registerMBean(mbean, name);

System.out.println("Agent is running...");

Thread.sleep(Long.MAX_VALUE);

}

}


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Agent

Management of resources are performed by JMX agent

Agent includes set of services to manage MBeans

Agent contains a managed object server (MBean Server)

MBeans are registeredin MBean Server

JConsole

$ java -Dcom.sun.management.jmxremote MemoryAgent

allows monitoringon the host

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Code Snippets

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// Lookup MBeanServer from the JNDIInitialContext initCtx = newInitialContext();

MBeanServer mbs = (MBeanServer) initCtx.lookup("jmx");

ObjectName name;

...

mbs.setAttribute(name, newAttribute("Test", "test value"));

Connecting to MBean Server

Access to an MBean

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mbs.invoke(ObjectNamename, StringoperationName, Object[] params, String[] signature)

throws InstanceNotFoundException, MBeanException, ReflectionException

Invoking an MBean Operations

// the query returns a set of matching ObjectNames

Set names = mbs.queryName(pattern, null);

Query an MBean
http://java.sun.com/j2se/1.5.0/docs/api/javax/management/ObjectName.htmlhttp://java.sun.com/j2se/1.5.0/docs/api/java/lang/String.htmlhttp://java.sun.com/j2se/1.5.0/docs/api/java/lang/Object.htmlhttp://java.sun.com/j2se/1.5.0/docs/api/java/lang/String.htmlhttp://java.sun.com/j2se/1.5.0/docs/api/javax/management/InstanceNotFoundException.htmlhttp://java.sun.com/j2se/1.5.0/docs/api/javax/management/MBeanException.htmlhttp://java.sun.com/j2se/1.5.0/docs/api/javax/management/ReflectionException.htmlhttp://java.sun.com/j2se/1.5.0/docs/api/javax/management/ReflectionException.htmlhttp://java.sun.com/j2se/1.5.0/docs/api/javax/management/MBeanException.htmlhttp://java.sun.com/j2se/1.5.0/docs/api/javax/management/InstanceNotFoundException.htmlhttp://java.sun.com/j2se/1.5.0/docs/api/java/lang/String.htmlhttp://java.sun.com/j2se/1.5.0/docs/api/java/lang/Object.htmlhttp://java.sun.com/j2se/1.5.0/docs/api/java/lang/String.htmlhttp://java.sun.com/j2se/1.5.0/docs/api/javax/management/ObjectName.html


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Thank you!

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