AnaBransonPart No: 806-2983December 1999Sun Microsystems, Inc.

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1999Sun MicrosystemsThe Getting Started with the Java Dynamic Management Kit 4.0 Guide presents the the architecture of the Java Dynamic Management Kit, introducing the key concepts of the product and the development process. This book is aimed at anyone seeking an introduction to the components of the Java Dynamic Management Kit. Familiarity with the Java programming language model is assumed.This product or document is protected by copyright and distributed under licenses restricting its use, copying, distribution, and decompilation. No part of this product or related documentation may be reproduced in any form by any means without prior written authorization of Sun and its licensors, if any. Third party software, including font technology, is copyrighted and licensed from Sun suppliers. Federal Acquisitions: Commercial Software--Government Users Subject to Standard License Terms and Conditions.Sun, Sun Microsystems, the Sun Logo, Java, Java Dynamic Management, JavaBeans, the Java Coffee Cup logo, docs.sun.com, AnswerBook, AnswerBook2, and Solaris are trademarks or registered trademarks of Sun Microsystems, Inc in the U.S. and other countries. UNIX is a registered trademark in the U.S. and other countries, exclusively licensed through X/Open, Ltd.All SPARC trademarks are used under license and are trademarks or registered trademarks of SPARC International, Inc. in the U.S. and other countries. Products bearing SPARC trademarks are based upon an architecture developed by Sun Microsystems, Inc.DOCUMENTATION IS PROVIDED "AS IS" AND ALL EXPRESS OR IMPLIED CONDITIONS. REPRESENTATIONS AND WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE DISCLAIMED, EXCEPT TO THE EXTENT THAT SUCH DISCLAIMERS ARE HELD TO BE LEGALLY INVALID. Ce produit ou document est protégé par un copyright et distribué avec des licences qui en restreignent l'utilisation, la copie, la distribution, et la décompilation. Aucune partie de ce produit ou document ne peut être reproduite sous aucune forme, par quelque moyen que ce soit, sans l'autorisation préalable et écrite de Sun et de ses bailleurs de licence, s'il y en a. Le logiciel détenu par des tiers, et qui comprend la technologie relative aux polices de caractères, est protégé par un copyright et licencié par des fournisseurs de Sun.Sun, Sun Microsystems, le logo Sun, Java, Java Dynamic Management, JavaBeans, Java Coffee Cup logo, docs.sun.com, AnswerBook, AnswerBook2 et Solaris sont des marques de fabrique ou des marques déposées de Sun Microsystems, Inc. aux Etats-Unis et dans d'autres pays. UNIX est une marque enregistrée aux Etats-Unis et dans d'autres pays, et exclusivement licenciée par X/Open Ltd.Toutes les marques SPARC sont utilisées sous licence et sont des marques de fabrique ou des marques déposées de SPARC International, Inc. aux Etats-Unis et dans d'autres pays. Les produits portant les marques SPARC sont basés sur une architecture développée par Sun Microsystems, Inc.LA DOCUMENTATION EST FOURNIE "EN L'ETAT" ET TOUTES AUTRES CONDITIONS, DÉCLARATIONS ET GARANTIES EXPRESSES OU TACITES SONT FORMELLEMENT EXCLUES DANS LA MESURE AUTORISÉE PAR LA LOI APPLICABLE, Y COMPRIS NOTAMMENT TOUTE GARANTIE IMPLICITE RELATIVE À LA QUALITÉ MARCHANDE, À L'APTITUDE À UNE UTILISATION PARTICULIÈRE OU À L'ABSENCE DE CONTREFAÇON.Introduction & OverviewJavaNetwork SoftwareProgramming & ToolsPrefacePrefaceThe Java Dynamic Management Kit provides a set of Java classes and tools for developing management solutions. This product conforms to the specification of the Java Management extensions (JMX) which define a three-level architecture: resource instrumentation, dynamic agents and remote management applications. Such an architecture is applicable to network management, remote system maintenance, application maintenance and service provisioning. The Getting Started with the Java Dynamic Management Kit 4.0 Guide presents the architecture of the Java Dynamic Management Kit, introducing the key concepts of the product and the development process.This book is aimed at anyone seeking an introduction to the concepts and components of the Java Dynamic Management Kit. Familiarity with Java programming and the JavaBeans component model is assumed. This book is not intended to be an exhaustive reference: management tutorials intended to demonstrate each of the management levels and how they interact are covered in Java Dynamic Management Kit 4.0 Tutorials, and the complete Javadoc API definitions are provided in the product documentation package.In order to build and run the sample programs in these tutorials, or use the tool commands, you must have a complete installation of the Java Dynamic Management on your machine. Please refer to the Java Dynamic Management Kit 4.0 Installation Guide and Release Notes document for instructions on how to install the product components and configure your environment.After familiarizing yourself with the concepts of the Java Dynamic Management Kit, you should familiarize yourself with the tools provided with the Java Dynamic Management Kit and learn how to instrument new or existing resources for management. The following books are part of the product documentation set:Java Dynamic Management Kit 4.0 Tools ReferenceJava Dynamic Management Kit 4.0 TutorialsThese books are available on-line after you have installed the documentation package of the Java Dynamic Management. The on-line documentation also includes the Javadoc API for the Java packages and classes, including those of the Java Management extensions. Using any web browser, open the home-page corresponding to your platform:Operating EnvironmentHome-Page LocationSolarisinstallDir/SUNWjdmk/jdmk4.0/JDKversion/index.htmlWindows NTinstallDir\SUNWjdmk\jdmk4.0\JDKversion\index.htmlIn these file names, installDir refers to the base directory of your Java Dynamic Management installation. The JDKversion is that of the Java Development Kit which you use and which you selected during installation; it can be either 1.1 or 1.2. This convention is used throughout this book whenever referring to files or directories which are part of the installation. In a default installation procedure, installDir is:/opt on the Solaris platformC:\Program Files on the Windows NT platformThis book explains the key concepts of the Java Dynamic Management Kit, introduces the main components of the product, provides an overview of the development process and outlines the tools you need to use the Java Dynamic Management Kit. It is divided into the following sections:"What is the Java Dynamic Management Kit ?""The Java Dynamic Management Kit Development Process"The Java Dynamic Management Kit relies on the management architecture of the Java Management extensions. The three specifications documents are provided in the product documentation package:"Java Management Extensions Instrumentation and Agent Specification" (jmx_instr_agent.pdf)"Java Management Extensions SNMP Manager API" (jmx_snmp_api.pdf)Fatbrain.com, an Internet professional bookstore, stocks select product documentation from Sun Microsystems, Inc.For a list of documents and how to order them, visit the Sun Documentation Center on Fatbrain.com at http://www1.fatbrain.com/documentation/sun.Sun Documentation OnlineThe docs.sun.com Web site enables you to access Sun technical documentation online. You can browse the docs.sun.com archive or search for a specific book title or subject. The URL is http://docs.sun.com.The following table describes the typographic changes used in this book.Table P-1 Typeface or SymbolMeaningExampleAaBbCc123Book titles, new words or terms, or words to be emphasizedRead Chapter 6 in User's Guide. These are called class options. You must be root to do this.AaBbCc123Class or object names, methods, parameters or any other element of the Java programming languageInstantiate the MyBean class.AaBbCc123The names of commands, files, and directories; on-screen computer outputEdit your .login file. Use ls -a to list all files. machine_name% you have mail.AaBbCc123What you type, contrasted with on-screen computer outputmachine_name% su Password:AaBbCc123Command-line placeholder: replace with a real name or valueTo delete a file, type rm filename.The following table shows the default system prompts for the different platforms and shells.Table P-2 ShellPromptC shell promptmachine_name%C shell superuser promptmachine_name#Bourne shell and Korn shell prompt$Bourne shell and Korn shell superuser prompt#Windows NT system promptC:\Unless otherwise noted, the command examples in this book use the Korn shell prompt.Chapter 11. What is the Java Dynamic Management Kit ?The Java Dynamic Management Kit is a Java based solution for building and distributing management intelligence into system, application, and network devices. It achieves this by providing a set of Java classes and tools that simplify the development of dynamically extensible agents.An agentagent is an application which provides one or more services. Agents act as invisible assistants, alerting you to potential problems throughout the network or performing management tasks without human intervention. Agents are smart, autonomous, and dynamic. They can download management services from the management web server, pulling new management services as soon as they become available. This allows new management services to be implemented and started at any time.Firstly, network management, under the current paradigm, is performed by management applications. These management applicationsmanagement applications are aided by agents. The agents act as interpreters and filters, sending commands to the network elements they control and collecting information about them. They are usually situated near the network elements they control, which means that these agents are limited in nature, as they contain little management intelligence and can only perform basic network management operations. Secondly, and from a wider perspective, existing system, application, and network management systems are implemented with diverse protocols and technologies. Developers must choose a single management technology for a portion of the target market. In some cases, developers may implement multiple management technologies, in order to provide more complete coverage of their potential markets. Frequently, developers choose not to implement any management technology, in order not to be encumbered in the market.The Java Dynamic Management Kit solves both of these problems. It is a single suite of products offering a uniform instrumentation for managing system, application, and network management systems. It is also a key enabling technology for the service-driven networkservice-driven network. The service-driven network is a new approach to the provision of network computing that concentrates on the services you want to provide. These services range from the low-level services that manage relationships between networked devices to the value-added services you provide to end-users. These services drive your network. With the Java Dynamic Management Kit, services are incorporated directly into agents. Agents are granted permission to perform management tasks themselves, enabling management intelligence to be distributed throughout the whole network.Thus, the Java Dynamic Management Kit opens the door to new types of lightweight, flexible management applications that can be created, deployed, enhanced or deleted in real time. The Java Dynamic Management Kit is different in that it offers more functionality than any other network management product of its kind. This unique combination of features gives the Java Dynamic Management Kit a wide domain of application.The Java Dynamic Management Kit supports management protocols, such as SNMPSNMP. It also uses a dynamic web-based pull mechanism enabling new services to be downloaded from the Web server at runtime. Services are not only implemented inside devices, but can also be network-based, stored as files in very simple Web pages in the same way as Java technology-based applets. This dynamic, on-demand paradigm means that it is no longer necessary to know what will need to be configured, managed, and monitored in the future or in advance of network deployment. servicesServices can be created and downloaded as needed. Autonomous management functionality is yet another key feature of the Java Dynamic Management Kit, allowing a very large installed base to be managed.The Java Dynamic Management Kit relies on Java Management extensions (JMX)Java Management extensions (JMX) principles to manage resources. In order to ensure that your resource is a manageable resource, you need to make sure that it adheres to the JMX specification, as the JMX instrumentation level provides a specification for implementing JMX manageable resources. Manageable resources are implemented as Managed Beans, or simply MBeans. An MBeanMBean is a manageable resources that conforms to certain design patterns and may be any resource you wish to manage (for example, an application, an implementation of a service, a device, a user, and so forth). These resources are developed in Java, or at least offer a Java wrapper, and have been instrumented so that they can be managed by JMX-compliant applications. For more information regarding MBeans, please refer to "MBeans".The Java Dynamic Management Kit is the first commercial product to implement the public specification for the Java Management extensions (JMX). JMX defines an architecture, design patterns, APIs, and services for application and network management, all under a single umbrella specification. For more information regarding JMX, see the Java Management Extensions specifications document provided with the Java Dynamic Management Kit.One of the greatest advantages of the Java Dynamic Management Kit is that it allows you to manage resources from a remote location. Thus, you can manipulate proxy objectsproxy objects which transparently map onto MBeans in a remote agent. You can access all remote JMX manageable resources by:Getting an attribute valueChanging an attribute valueInvoking an operationReceiving a notification emitted by a manageable resourceThe manager can also add new remote JMX manageable resources by:Using existing Java classes already loaded in the agentUsing new classes downloaded from an arbitrary locationThe Java Dynamic Management Kit greatly simplifies the development of management applications by providing multi-protocol communicationSee also SNMP, HTTP/TCP, RMImulti-protocol communication between the manager side and the agent side. Devices or applications can be managed directly via a basic Web browser or through an existing SNMP management application. An extensible set of protocol adaptors (for example, HTTP/TCP, RMI, SNMP) is provided to allow developers to adapt their applications to the local communication environment. To create brand new agents, use a managed object generator (proxygen)See proxygenmanaged object generator (proxygen), which is provided with the Java Dynamic Management Kit. With this tool, you can create applications with automatically-generated remote access modules that handle communication support and protocol transparency. Simply put, you can create a proxy objectproxy object for each JMX object you wish to manage remotely.The Java Dynamic Management Kit also provides a toolkit for developing SNMPSNMP agents and managers, including the mibgen compiler, which takes as input a set of SNMP MIBs and generates standard MBeans that implement the MIBs.The Java Dynamic Management Kit provides:A management archictecturemanagement architecture which supports the JMX specification. This architecture, in turn, provides a set of Web-based mechanisms for automatic propagation of management services across the network to the agents. An agent frameworkagent framework, which includes a library of reusable core agent services in the form of management components based on the JavaBeans architecture. New services can be plugged in and old services removed as management requirements evolve. The services supplied include the following: monitoring, timer, mlet, and filtering.Service creation tools, which include: A managed object generatorSee proxygenmanaged object generator (proxygen), which helps developers to create their own specific Java technology-based client management services. A Java technology-based SNMP MIB Compiler (mibgen) which takes an SNMP MIB as input and outputs a set of Managed Beans. These MBeans implement the MIBs, enabling the JDMK agent to be managed by an SNMPSNMP manager. Java Management extensions (JMX)key conceptsFigure 1-1 below shows the key concepts for the Java Dynamic Management Kit. The five keywords are MBean server, MBeans, adaptors, connectors, and proxy MBeans.

Figure 1-1

The MBean serverMBean server, referred to as the framework in previous releases, is a registry for JMX manageable resources which are exposed to management operations in an agentagent. It provides a management framework with services for manipulating JMX manageable resources that is protocol-independent and information model-independent. All management operations performed on these resources are done through the MBean server management interface. You can create and manage objects by registering them within the MBean server, thus, making them visible to management applicationsmanagement applications. The MBean server includes a library of reusable core agent services in the form of manageable objects, as specified by Java Management extensions (JMX). These services include mlet, timer, monitoring and filtering.Java Management extensions (JMX)MBeanYou can register objects in the MBean serverMBean server through: The agent application itselfA remote management application (through a connector or a protocol adaptor)Any JMX manageable resource that you want to access for management operations must be registered in the MBean server. This MBean needs to be assigned a unique object name. The manager and the agent then use this object name to identify the object on which it is to perform a management operation. If you do not specify the object name explicitly, the MBean implementation may itself provide a name by default. It is possible to have multiple MBean servers within the same Java Dynamic Management Kit agent.JMX's instrumentation level provides standards for implementing JMX manageable resources. The instrumentation of a given manageable resource is provided by one or more Managed Beans, or MBeans (previously written m-beans). An MBeanMBean is a Java object that conforms to certain design patterns for exposing attributes and operations. These attributes and operations enable any Java Dynamic Management agent to recognize and manage the MBean. The design patterns for MBeans give the developer explicit control over how a resource, device or application will be managed. For example, attribute patterns enable you to make the distinction between a read-only and a read-write property in an MBean. The set of all attributes and operations exposed to management through the design patterns is called the management interfacemanagement interface of an MBean. MBeans implement a management interface which defines the attributes and operations accessible for management. Any object that you want to make accessible through the MBean server must be represented as an MBean, including the resources you want an agentagent to manage and any servicesservices that you want to provide to manage these resources. MBeans can both generate and propagate notification events to remote management applicationsmanagement applications. For more information regarding managing MBeans remotely, please refer to "Proxy MBeans" and "Generic Proxy MBeans". MBeans must be developed according to the rules specified by Java Management extensions (JMX)Java Management extensions (JMX).The JMX architecture enables you to carry out certain operations on a particular agent, by going through that agent's MBean server. These operations are as follows:Manage existing MBeans by:Listing MBeansEnabling MBean attributes to be accessed both locally and remotelyEnabling new MBeans to be instantiated and registered both locally and remotelyPerforming operations defined by the MBeansReceiving notifications emitted by MBeansDiscovering the management interfacemanagement interface of MBeansAllowing you to develop a generic managerProviding a view of the MBean through a specific protocolYou can manage a new MBean as soon as it is registered within the MBean serverMBean server. An MBean can be created and registered by:Another object within the agentagentA remote managment applicationmanagement application connected to the agentMBeans can also be downloaded from a Web server and plugged into an agent at any time, in response to a demand by the management application. This is called dynamic class loadingdynamic class loading and means that future services and applications can be loaded on-the-fly and without downtime once they have been deployed on the network. For example, dynamic class loading can be used to provide rapid, low-cost delivery of end-user applications across very large bases of Java technology-enabled devices, such as desktop PC's or Web phones.The management services supplied with the Java Dynamic Management Kit are implemented as MBeans. You can also write the MBeans representing objects you wish to manage. These objects could include the actual resources you want to manage and the value-added services provided to help manage resources. The Java Dynamic Management Kit does not impose any restrictions on where compiled MBean classes are stored. They can be stored at any location specified in the CLASSPATH environment variable of the agent, or at a remote site. Managed ObjectsYou can develop two types of MBeans:Standard MBeansDynamic MBeansMBeans, StandardStandard MBeans are Java objects that conform to certain design patterns derived from the JavaBeans component model. Standard MBeans allow you to define your management interface as a Java Interface and this interface, in turn, defines the handles that are exposed to management of that particular resource. The methods for reading and writing the MBean's attributes and for invoking its operations are described in this management interfacemanagement interface. Standard MBeans are defined statically, in that the elements of their management interface are defined at compilation time and cannot be controlled or altered at runtime. They are the quickest and easiest type of MBeans to implement when you want to create new MBeans for new manageable resources where their data structure is defined in advance and is unlikely to change often.MBeans, DynamicDynamic MBeans allow your application or domain specific manager to define the management interface for a resource at run time. This provides a simple way to wrap existing non-MBean style or even non-Java technology based resources and offers greater flexibility than standard MBeans. Dynamic MBeans are more suited to management structures that change over time and are, hence, dynamic. Dynamic MBeans allow manageable resources to be flexible because they have a pre-defined interface which allows attributes and operations to be exposed only at run time.MBeans, ProxyA proxy MBeanproxy MBean (referred to as a client bean or c-bean in previous releases) represents the manager view of the managed MBean, where the manager has been developed using the remote MBean serverMBean server interface. This interface makes the functionality of the MBean server available in the remote management application (also referred to as the manager) and lets the manager interact directly with the MBean server of the agent, or instantiate proxy MBeans to manipulate remote MBeans transparently.The manager accesses an MBean by performing operations on the proxy MBean, which are then propagated to the MBean. These operations are: Getting or setting attributesOperation invocationsNotifications emitted by the MBean are propagated to the remote manager applicationA Proxy MBean is generated from an MBean by using the proxygen compiler, supplied with the Java Dynamic Management Kit. A proxy MBean can only be generated from a standard MBean and is created to mirror an existing MBean. Proxy MBeans are ideal when the management interface does not need to change over time, hence, where the attributes and operations available are stable. Managed Object GeneratorSee proxygenMBeans, Generic ProxyA generic proxy MBean acts in the same manner as a proxy MBean. However, you do not generate generic proxy MBeans using the proxygen compiler as with proxy MBeans, but simply by creating a new instance of a generic proxy MBean. Generic proxy MBeans are ideal when you want to perform operations on one MBean and when you know that the attributes and operations of that MBean will change. For example, sometimes you may have write permissions on an attribute and other times you may only be able to read the attribute. This makes generic proxy MBeans the perfect solution for dynamic management systems, where an MBean's properties are likely to change at run time. Generic proxy MBeans can be used to manage either standard MBeans or dynamic MBeans, thus, can mirror both types of MBeans.MBeans, StandardMBeans, DynamicConnectors and Protocol Adaptors allows an agent to be accessed and managed by remote custom management applications. These applications could be outside the agent's Java Virtual Machine (JVM). This can be seen in the previous illustration, Figure 1-1 .Connectors (referred to as adaptors in previous releases) connect the MBean server to management applications and enable MBeans to be instantiated and managed remotely. Every connector provides the same remote management interface, but through a different protocol, which allows remote management applications to connect to agents transparently through the network, regardless of the specific protocol. One or more connector clients can be connected to the MBean server, providing views through specific protocols of the MBeans instantiated and registered with the MBean serverMBean server. The Java Dynamic Management Kit provides connectors for most major internet protocols (for example, HTTP/TCPSee also RMIHTTP/TCP and RMI) .Multi-Protocol CommunicationA connector is composed of two parts:A connector server on the agent sideA connector client on the manager sideThe interface of the remote MBean server is implemented by the connector client. Connectors allow management applications to be transposed onto a manager site, offering the same level of functionality at both the agent and manager side while ensuring seamless, transparent connectivity.Protocol Adaptors have only a server component and provide connection between a remote management application and an agent, via a specific network protocol. From a manager side, you can view and manage all MBeans registered in the MBean server. This can be achieved by directly accessing the MBean server's interface through a given protocol. For example, a web browser accesses the HTMLHTML protocol adaptor directly and, therefore, a client of the HTML protocol adaptor is an HTML browser. Similarly, an SNMPSNMP manager accesses the SNMP adaptor directly. Therefore, a client of the SNMP adaptor is an SNMP manager. In addition, the Java Dynamic Management Kit provides an SNMP toolkit that allows you to generate MBeans that support standard or proprietary MIB's, enabling new Java technology-based agents to be integrated into existing network infrastructures, including most SNMP-based management products.Connectors and protocol adaptors enable management applications to:Find existing MBeans through their object namesGet or set attributes of existing MBean instancesInvoke operations on existing MBean instancesInstantiate an MBean and register the new MBean instanceReceive notifications from known MBeans (except through the HTML adaptor)For an agent to be managed remotely, it must include at least one connector or protocol adaptor. However, an agent can include any number of connectors or protocol adaptors, enabling it to be managed remotely by many managers, through different protocols. Proxy MBeans, at the manager side, are used to perform management operations on the corresponding MBeans at the agent side. These MBeans are registered with the MBean serverMBean server in a manner that is protocol-independent. Neither connectors nor protocol adaptors are automatically started when they are created, which allows you to specify the port number before you start them.Agent, ManagedThe management interface of an MBean allows an MBean's agent to perform control and configuration operations on the managed resources. The JMX MBean notification model allows MBeans to broadcast management notifications. Management applicationsManagement applications and other objects register as listeners with the broadcaster MBean. The JMX MBean notification model enables a listenerlistener to register only once and still receive all different notifications that may occur in the broadcast.

Figure 1-2

Figure 1-2 illustrates the remote notificationremote notification mechanism. This can be seen in terms of the Pull mechanism and the Push mechanism. If you want to add a listenerlistener of notifications at the agent side you need to call the addNotificationListener method on the MBean server. In this case, the notification will not be forwarded to the connector client. You can also add a listener, addNotificationListeneron the remote MBean serverMBean server or on proxy MBean A.MBean, ProxyThere are two ways you can add a listener to the manager side. Firstly, you can call the appropriate addNotificationListener operation on proxy MBean A. This will transmit a call to the agent side and a protocol-dependent, appropriate listener will be created in the MBean server (L1 in Figure 1-2). This is a protocol-dependent, generated listener and is handled by the connector server. It is in charge of sending notifications throughout the network, from the agent side to the manager side, using a specified protocol. Secondly, you can call the addNotificationListener method on the remote MBean server.You can choose to use the Push Mechanism to push notifications from an agent to a manager. When the connectors run employ the Push Mechanism the connector server forwards the notifications to the connector client as soon as they are emitted by the MBeans. For example, you can register proxy MBean A as a listener of notifications emitted by MBean A. Thus, when MBean A, at the agent side, emits a notification, the HTTP or RMI adaptor forwards this notification to the connector client at the manager side. MBean server, remoteYou can choose to use the Pull Mechanism to forward notifications from an agent to a manager. This is useful, for instance, when the agent is unable to connect to a manager. For example, if there is a fire-wall in place between the agent side and the manager side. You can use the Pull Mechanism to pull notifications from the agent side to the manager side. When you create the remote MBean server you need to set the mechanism mode and the pull period. The pull period is the time period between pulls. Pulls occur when the HTTPSee also RMIRMISee also HTTPHTTP/RMI connector server at the agent side is instructed by the manager to attempt to pull notifications. Thus, the manager decides when, and how often, it wants to retrieve notifications . For example, the pull frequency could be set to try to get notifications every thirty seconds or every minute.MBean server, remoteChapter 22. The Java Dynamic Management Kit Development Processdevelopment process, overview

Figure 2-1

The main steps in developing an application with the Java Dynamic Management Kit are:Creating new MBeans/ adapting existing resources through instrumentationRegistering MBeansTesting the MBeans with a web browserOptional: generating proxy MBeansDeveloping a manager As discussed earlier in "Key Concepts", MBeans conform to the Java Management extensions (JMX)JMX specification, which formalizes the representation of the MBean's management interfacemanagement interface. Management interfaces are represented as attributes and operations which you can invoke. You must create new MBeans which adhere to the design patterns for exposing these attributes, specified by JMX. The design patterns for developing MBeans are specific to the MBean model, and are defined to ease the interaction between objects and the MBean serverMBean server. You may also select MBeans from those included in the toolkit and customize them, using a Java Development Environment in order to generate MBeans for the services you require. managed objectsAttributes define the appearance or behavior of an MBean or are attributes of the managed resource that the MBean represents. For example, an attributeattribute named ipackets in an MBean representing an Ethernet driver could be defined to represent the number of incoming packets. Attributes can have arbitrary types, including built-in Java types, and class or interface types such as java.awt.Color.Attributes are always accessed via operation calls on the object that owns them. For readable attributes, there is a getter operation to read the attribute value. For writable attributes, there is a setter operation to allow the attribute value to be updated. By default, the following design pattern is used for identifying attributes:public attributeType getattributeName(); public void setattributeName(attributeType value);If a class definition contains a matching pair of getattributeName() and setattributeName() operations these operations define a read-write attribute. If a class definition contains only one of these operations the operation defines either a read-only or write-only attribute called attributeName.To enable an MBean to be managed by a Java Dynamic Management agent, register it in the MBean server. Registering an MBean does not necessarily require any modification of code. You can write the MBean so that it can control its own registration, should you wish to do so. An MBean is registered by code in the agent which is to manage the MBean's resources. The Java Dynamic Management Kit enables you to register an existing MBean instance or to instantiate and register an MBean in a single operation. When registered, an MBean is assigned an object name by the user. If the user does not give the object a name then the object can assign a name for itself.An MBean can also be instantiated and registered remotely by code in a Java Dynamic Management client.Regardless of the registration operation, the MBean server generates a notification whenever an MBean is registered. The information sent with the notification includes the object name of the new MBean. After you have compiled your MBean classes, you are able to use a web browser to test them. You do this by connecting a web browser to a running agent (for example, the base agent), instantiating MBeans, and performing other operations on the MBean instances. Before connecting a web browser to an agent, make sure that:The agent is running on a machine that you can access by using the HTTPHTTP protocolThe agent contains an instance of HTMLHTML adaptorThe compiled MBean classes are stored at a location specified in the CLASSPATH environment variableCLASSPATH environment variable of the agentTo use a web browser to communicate with an agent, open the page given by the following URL in a web browser:http://host:portwhere:host is the host name of the machine on which the agent is runningport is the port number used by the HTML adaptor in the agent; the default port number is 8082The HTML page displayed is generated by the HTML adaptor and enables you to perform the following operations on MBeans in the agent:Reading or writing the attributes of an MBean instancePerforming an operation on an MBean instanceInstantiating an MBeanDeleting an MBeanMBean instanceMBean, ProxyAs discussed earlier in this guide, a proxy MBean is an object that represents a remote MBean to a Java Dynamic Management manager. The manager accesses an MBean by performing operations on the proxy MBean. The operations are then propagated to the MBean.A proxy MBean is generated from its MBean by using the proxygenSee Managed Object Generatorproxygen compiler supplied with the Java Dynamic Management Kit. A generic proxy MBean can be created by simply creating an instance and, hence, there it is not generated using the proxygen compiler. The MBean's input to proxygen must be in the form of compiled Java classes, not source files. The numerous options of this tool allow you to customize your MBeans depending on how you wish to use them in your management application.A proxy MBeanproxy MBean consists of two components: A Java interface that defines which of the operations of the MBean are accessible to a Java managerA Java class that implements the operations defined in the Java interfaceMBean, ProxyFor example, if you have an MBean MyClass, the proxygen compiler gives you a proxy MBean that consists of the following files:MyClassProxyMBean.java - the Java interfaceMyClassProxy.java - the Java classThe proxygen compiler generates Java source code, not compiled Java classes. For your proxy MBeans to be accessible to a Java manager, you have to compile the files that proxygen generates, and make sure that the compiled Java classes are stored at the location specified by the CLASSPATH environment variableCLASSPATH environment variable of the manager, or are accessible by the class loader of the manager.A proxy MBean consists of:A Java interface that defines which of the operations of an MBean are accessible to a Java management applicationA Java class which implements the operations defined in the MBean's interfaceThe interface of a proxy MBean exposes the attributes and operations of the corresponding MBean. All operations have the same signature as in the original MBean, apart from the exceptions which are unique to the proxy MBean interface.The generated class provides an implementation for the proxy MBean's interface. Therefore, the Java class contains the code to implement the getters, setters and operations of the proxy MBean. To do this, the Java class relies on the com.sun.jdmk.comm.RemoteMBeanServer interface. This interface specifies the API for the connector client object which the management application uses to communicate with its agents. For example, the Java class implementation of a getter operation calls the appropriate operations of the interface. Through this interface, the corresponding getter operation of the MBean is called remotely, and its result is sent back to the proxy MBean.The generated class implements the com.sun.jdmk.Proxy interface in order to provide additional management capabilities. As the interface is used by all connector client objects in the Java Dynamic Management Kit, all proxy MBeansproxy MBeans can be connected to their corresponding MBean through any of the communication protocols. It also guarantees that the behavior of the proxies is not affected by how the connector client is implemented. The proxygen compiler takes the compiled Java class of an MBean and generates the Java interface and Java proxies of a proxy MBean. The Java proxies consist of Java source code that implements the interface. To develop a Java manager with code generated by proxygen, you call the operations of the proxy MBean's interface. This allows you to remotely manipulate the corresponding MBean on an agent. Options of the proxygen compiler enable you to modify the characteristics of the proxies you generate from an MBean. For example, options are available that enable you to generate read-only or read-write proxies. By generating a set of stubs with different characteristics from the same MBean, you can develop a Java ManagerJava manager whose behavior is modified at runtime, depending on which stubs are loaded. For example, when the read-only stubs are loaded, the Java manager will not be able to modify properties in the MBean.To start proxygen, type the command for your operating environment:In a Solaris operating environment:prompt% installDir/SUNWjdmk/jdmk4.0/1.1 or 1.2/bin/proxygen <options> < classes>In a Windows NT operating environment:C:\> "installDir\SUNWjdmk\jdmk4.0\1.1 or 1.2\bin\proxygen" <options> < classes>You can develop a manager in the Java language by using the connector client management interface. The main steps in developing a Java manager are:Initializing a connector clientAdding and Implementing a Connector/Protocol Adaptor to an AgentControlling access by a manager to an agentAdding the services that the connector client requires in order to operate (refer to "Agent Services")Instantiating MBeans in an agentGetting or setting attributes of MBeansPerforming operations on MBeansA connector provides access to MBeans through a communication protocol. It enables management applications to perform management operations on a Java Dynamic Management agent. For a Java Dynamic Management agent to be manageable, it must contain at least one connector. However, a Java Dynamic Management agent can contain many protocol adaptors, allowing it to be managed remotely through different protocols.The following connectors/protocol adaptors are supplied with the Java Dynamic Management Kit:RMIRMIHTTP/TCPHTTP/TCPHTMLHTMLSNMPSNMPMulti-Protocol CommunicationThe RMI connector enables Java managers to access a Java Dynamic Management agent using the Java remote operation invocation (RMI) system. The HTTP/TCP connector enables Java managers to access a Java Dynamic Management agent using HTTP over a TCP/IP connection. It also allows these management applications to access an agent across proxy servers. By default, the HTTP/TCP adaptor listens for incoming requests on port 8081. The HTTP/TCP connector provides login/password authentication. The HTML protocol adaptor is an HTML server that enables web browsers to access a Java Dynamic Management agent through the HTTP communication protocol. When an HTML protocol adaptor is instantiated, it creates a TCP/IP socket and waits for incoming requests. By default, the HTML adaptor listens for incoming requests on port 8082. The HTML adaptor provides login/password authentication. The HTML protocol adaptor is provided as a tool for debugging and speeding the development of agents. As such, it has certain limitations, for example it does not display complex types or multi-dimensional arrays. SNMPThe SNMP protocol adaptor enables an SNMP manager to perform management operations on a Java Dynamic Management Kit agent. Before using the SNMP protocol adaptor, you need to configure it for the MIB used by the SNMP manager application. To add a connector/protocol adaptor to an agent, create an instance of the Java class that implements the connector/protocol adaptor you want to use.AdaptorJava ClassRMIcom.sun.jdmk.comm.RmiConnectorServerHTTP/TCPcom.sun.jdmk.comm.HttpConnectorServerHTMLcom.sun.jdmk.comm.HtmlAdaptorServerSNMPcom.sun.jdmk.comm.SnmpAdaptorServerThe Java Dynamic Management Kit provides the following ways to add a connector/protocol adaptor to an agent:A connector/protocol adaptor is an abstraction of a communications protocol. This means that the communication mechanism between agent and manager is hidden. The connectors/protocol adaptors provided by the Java Dynamic Management Kit are implemented as MBeans. This enables them to be managed. The Java Dynamic Management Kit does not require a connector/protocol adaptor to conform to a specific interface definition or implementation. However, a connector/protocol adaptor must be able to access the MBean server to retrieve and change information in MBeans in an agent.The Java Dynamic Management Kit provides mechanisms for controlling access by a manager to an agentagent. The access control operations available depend on the connector/protocol adaptor used. The HTTP connector and HTML protocol adaptor both provide login/password authentication.The SNMP protocol adaptor provides access control using information contained in an access control (ACL) file.The SNMP protocol adaptor can also provide access controlaccess control using information contained in an access control object.The Java Dynamic Management Kit does not provide access control for the RMI connector.The HTTP/TCP connector and the HTML protocol adaptor provide login/password authentication. In this authentication scheme, the client object and the server object contain authentication information. The server side object contains an array of objects that contain authentication information for all known clients. When a client attempts to login, the login/password object that it sends is compared with the array to see if the client is on the list of permitted clients. If the list of permitted clients is null, no client authentication is performed by the adaptor and access is granted to all clients.A connector client enables a Java manager to access MBeans in a remote agent through a particular communications protocol. The Java Dynamic Management Kit provides a connector client for each of the protocols supported . All connector clients have the same interface, meaning that the manager is protocol-independent. Connector client objects are the objects that management applicationsmanagement applications use to communicate with the agentsagents that they wish to manipulate. These objects establish a connection to a corresponding connector server in an agent, through the specific protocol they implement. There is thus one connector server and client pair for each protocol supported.Connector, ServerConnector, clientA connector client enables Java managers to perform management operations on a Java agent. Connector clients provide a level of abstraction by allowing a manager to manipulate local objects, the effects of which are remote. The manager does not need information on the protocol used to communicate with the agent; it needs either the class name or object name of the objects to be managed. There are two ways for a manager to interact with its connector client:The management application can call the operations of the connector client to interact with remote MBeans directlyMBean, RemoteThe application can have the connector client instantiate local proxy MBean objects which represent each MBean in a remote agent; in this case, the manager calls the operations of the proxy MBeanproxy MBean, derived from its corresponding MBean.MBean, ProxyThe proxy MBeans themselves rely upon the remote MBean server interface; they provide simplified access to the remote objects. In both cases, a manager must have information on the semantics of the MBeans it manages. It is much easier to write a management application using proxy MBeans, rather than calling the remote MBean server interface. However, this requires that the appropriate proxy MBean objects be available to the management application. Manipulating proxy MBeansproxy MBeans also uses more memory resources as they are instantiated objects.MBean server, remoteJava managers access a connector through a connector client. The Java Dynamic Management Kit provides connector clients to enable a Java manager to access a connector using these protocols: Connector, ClientRMIRMIHTTP/TCPHTTP/TCPThe purpose of a protocol adaptor is to enable a manager to:Read and, if allowed, set attributes of MBeansInvoke operations on MBeansReceive notifications emitted by MBeansRequest that MBeans are instantiated, registered and deregisteredWhen a request from a manager to instantiate and register an MBean is carried out, the Java class of the MBean needs to be specified. The code of the class does not have to be present on the same machine as the agent in which the MBean is to be instantiated.These types of management applicationsmanagement applications access adaptors directly:Web browsers accessing the HTMLHTML adaptorSNMPSNMP managersBenefits of the Java Dynamic Management Kit include:Dynamic extensibility and scalabilityEasy management of Java applicationsEasy development of smart agentsProtocol independenceThe Java Dynamic Management Kit simplifies the development of extensible agents. An agent is able to instantiate Java classes loaded from an arbitrary location. Therefore, it is possible to extend the functionality of a running agent by making new classes available at an arbitrary location and requesting that the agent load and instantiate them.Agents developed using the Java Dynamic Management Kit are also scalable. MBeans can be registered and unregistered with the MBean serverMBean server in an agentagent while it is running. By registering and un-registering new MBeans, the agent can use only what it needs when it needs it. This feature enables the size and complexity of an agent to be modified while the agent is running, without having to stop the agent.agent, extensibleThe MBean server enables easy management of Java applications. For a Java application to be manageable, it only needs to be modified so that it:Instantiates the MBean server and a connectorRegisters the objects that, in conjunction with their states, accurately represent the applicationThe only restriction is that the registered objects have to be instances of an MBean. This is not a serious restriction, as it does not force the existing design to be changed, nor does it require a fixed class inheritance scheme. When you design an MBean, you do not need to explicitly take into account the interaction of the MBean with the MBean server or the adaptors. This is handled for you by the design patterns for MBeans. An application that includes the MBean server and a connectorconnector provides remote access for management operations without the need for any further development.Agents developed using the Java Dynamic Management Kit are smart agents. A smart agent provides the services needed to process management requests. In a smart agent, much of the processing can be done locally in the agent itself, reducing the load on the network connection between the agent and the manager. This also enables an agent to continue to work if the connection between it and its manager is lost.The design patterns for MBeans do not depend in any way on the protocol an agent uses for communicating with external applications. This is because the connectors interact with MBeans through the MBean server. New connectors (with new protocols) can be developed and used without rewriting existing MBeans or external applications. All that is required is that the new connector is able to interact with the MBean server. To simplify the development of agents for network, system, application, and service management, the Java Dynamic Management Kit supplies a set of agent services, which includes base services. Agent services are simply manageable resources, implemented as MBeans, that can perform management operations on other MBeans, thus, enabling agents to manage resources.The filtering service selects MBeans to be the subjects of management operations. Selection is based on the presence and values of specific attributes in object names. For example, a filter could select all the MBeans for which the attribute color is red. The filtering service is not implemented as an MBean. It is part of the infrastructure of the MBean server.The monitoring service observes numerical values and strings, enabling the variation over time of a attribute in an MBean to be monitored. The observed attribute is monitored at intervals specified by the granularity period. An event notification is sent when the value of the attribute satisfies one of a set of conditions, thus monitors can notify other objects of several types of changes in the target. You specify the conditions when you initialize a monitor.The timer service enables you to create notifications for specific dates and times, providing a scheduling mechanism based either on a one-time notification or on a repeated, periodic notification. The notifications or notification events are sent to all objects registered to receive timer events. This service performs a function similar to that of the cron daemon of the UNIX operating system. There are two types of timer notifications:One-time notificationPeriodic notification: a set number of occurrences at equal intervals over a given time periodThe management applet or m-let service enables an agent to obtain MBeans from a remote Java Archive (JAR) file. The agent does this by loading an m-let text file, which specifies information on the MBeans to be obtained. The information on each MBean is specified in a single instance of a tag, called an MLET tag. The location of the m-let text file is specified by a URL. When an m-let text file is loaded, an instance of each MBean specified in the file is created.The Java Dynamic Management Kit provides a toolkit for developing SNMPSNMP agents and managers. This includes:an SNMP agent toolkitDeveloping An SNMP AgentSNMP MIB Compiler -- mibgenSNMP Protocol AdaptorSNMP Manager APIDeveloping an SMNP Agent using the Java Dynamic Management Kit involves three steps:Generating Java code by running mibgen on the target SNMP MIBFilling in the access operations in the generated Java codeConfiguring the SNMP adaptor with the target MIBmibgen parses an SNMP MIB and generates the following:an MBean representing the whole MIBa class representing the metadata definitions for the MIB variablesclasses representing SNMP groups/entries as MBeans (and a metadata class for each instance generated)classes representing SNMP tablesclasses representing SNMP enumerated typesMBeans generated by mibgen need to be updated to provide the definitive implementation.SNMP agents developed with the Java Dynamic Management Kit are extensible in that MIBs can be added or removed during an agent's lifetime. They are open as SNMPSNMP is not the only protocol available and HTTPHTTP, HTMLHTML and RMIRMI protocol adaptors can also be used to access the agent. They can be SNMP-only because the SNMP adaptor can be used alone and the MBean server is not mandatory.For more information regarding this development process, please refer to the Java Dynamic Management Kit Tools Reference Guide.The mibgen compilermibgen compiler takes as input a set of SNMP MIBs and generates standard MBeans that implement the MIBs. MIBs can be expressed using SNMP v1 or SNMP v2 syntax. The mibgen compiler is able to process:Tables with cross references indexed across several MIBsMIBs that contain both v1 and v2 definitionsThe mibgen compiler also generates the Java source code required for representing a whole MIB in an SNMP manager. Table objects provide methods for adding and removing entries from the table.When the whole MIB file is registered in the MBean server, all the associated groups are automatically instantiated and added to the MBean server. The SNMP adaptor implements the SNMP v1 and v2 protocol stack. The protocol adaptor is able to manage an unlimited number of different Management Information Bases, commonly referred to as MIBs. By providing a unified view of all the MIBs, the SNMP adaptor solves the subagent problem that commonly occurs with SNMP. The SNMP protocol adaptor allows MIBs to be loaded or unloaded dynamically. This enables a MIB to be loaded into, updated, and unloaded from an agent while it is running.The SNMP manager API is a set of Java classes that simplifies the development of applications for managing SNMP agents. The agents may be developed using the Java Dynamic Management Kit, or by other means. IndexIndexaccess controlindexterm-90agentindexterm-2indexterm-20indexterm-27indexterm-33indexterm-89indexterm-107agent, extensibleindexterm-108Agent, Managedindexterm-53agent frameworkindexterm-15agentsindexterm-92attributeindexterm-69CLASSPATH environment variableindexterm-72indexterm-79connectorindexterm-109Connector, Clientindexterm-100Connector, clientindexterm-94Connector, Serverindexterm-93development process, overviewindexterm-64dynamic class loadingindexterm-35HTMLindexterm-50indexterm-71indexterm-85indexterm-104indexterm-113HTTPSee also RMIHTTP/TCPSee also RMIJava Management extensions (JMX)indexterm-7indexterm-18indexterm-22indexterm-30indexterm-65Java Managerindexterm-82key conceptsintro-ix2listenerindexterm-55indexterm-57Managed Object GeneratorSee proxygenmanaged object generatorSee proxygenmanaged object generator (proxygen)See proxygenManaged Objectsindexterm-36managed objectsindexterm-68management applicationsindexterm-3indexterm-21indexterm-29indexterm-91indexterm-103Management applicationsindexterm-54management archictectureindexterm-14management interfaceindexterm-26indexterm-31indexterm-38indexterm-66managment applicationindexterm-34MBeanindexterm-8indexterm-23indexterm-25indexterm-73MBean, Proxyindexterm-59indexterm-75indexterm-78indexterm-97MBean, Remoteindexterm-95MBean serverindexterm-19indexterm-24indexterm-32indexterm-42indexterm-47indexterm-52indexterm-58indexterm-67indexterm-106MBean server, remoteindexterm-60indexterm-63indexterm-99MBeans, Dynamicindexterm-39indexterm-46MBeans, Generic Proxyindexterm-44MBeans, Proxyindexterm-40MBeans, Standardindexterm-37indexterm-45mibgen compilerindexterm-115multi-protocol communicationSee also SNMP, HTTP/TCP, RMIMulti-Protocol Communicationindexterm-49indexterm-87proxy MBeanindexterm-41indexterm-77indexterm-96proxy MBeansindexterm-74indexterm-80indexterm-98proxy objectindexterm-12proxy objectsindexterm-9proxygenSee Managed Object Generatorremote notificationindexterm-56RMISee also HTTPservice-driven networkindexterm-4servicesindexterm-6indexterm-28SNMPindexterm-5indexterm-13indexterm-17indexterm-51indexterm-86indexterm-88indexterm-105indexterm-110indexterm-111Sun Documentation Onlineindexterm-1