javax.management (Java 2 Platform SE 5.0)

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Java^TM 2 Platform
Standard Ed. 5.0

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Package javax.management

Provides the core classes for the Java Management Extensions.

See:
Description

Interface Summary
Descriptor	This interface represents the behavioral metadata set for a JMX Element.
DescriptorAccess	This interface is used to gain access to descriptors of the Descriptor class which are associated with a JMX component, i.e.
DynamicMBean	Defines the methods that should be implemented by a Dynamic MBean (MBean that exposes a dynamic management interface).
MBeanRegistration	Can be implemented by an MBean in order to carry out operations before and after being registered or unregistered from the MBean server.
MBeanServer	This is the interface for MBean manipulation on the agent side.
MBeanServerConnection	This interface represents a way to talk to an MBean server, whether local or remote.
MBeanServerDelegateMBean	Defines the management interface of an object of class MBeanServerDelegate.
NotificationBroadcaster	Interface implemented by an MBean that emits Notifications.
NotificationEmitter	Interface implemented by an MBean that emits Notifications.
NotificationFilter	To be implemented by a any class acting as a notification filter.
NotificationListener	Should be implemented by an object that wants to receive notifications.
PersistentMBean	This class is the interface to be implemented by MBeans that are meant to be persistent.
QueryExp	Represents relational constraints that can be used in database query "where clauses".
ValueExp	Represents values that can be passed as arguments to relational expressions.

Class Summary
Attribute	Represents an MBean attribute by associating its name with its value.
AttributeChangeNotification	Provides definitions of the attribute change notifications sent by MBeans.
AttributeChangeNotificationFilter	This class implements of the `NotificationFilter` interface for the `attribute change notification`.
AttributeList	Represents a list of values for attributes of an MBean.
AttributeValueExp	Represents attributes used as arguments to relational constraints.
DefaultLoaderRepository	Deprecated. Use `MBeanServer.getClassLoaderRepository()` instead.
MBeanAttributeInfo	Describes an MBean attribute exposed for management.
MBeanConstructorInfo	Describes a constructor exposed by an MBean.
MBeanFeatureInfo	Provides general information for an MBean descriptor object.
MBeanInfo	Describes the management interface exposed by an MBean; that is, the set of attributes and operations which are available for management operations.
MBeanNotificationInfo	The `MBeanNotificationInfo` class is used to describe the characteristics of the different notification instances emitted by an MBean, for a given Java class of notification.
MBeanOperationInfo	Describes a management operation exposed by an MBean.
MBeanParameterInfo	Describes an argument of an operation exposed by an MBean.
MBeanPermission	Permission controlling access to MBeanServer operations.
MBeanServerBuilder	This class represents a builder that creates a default `MBeanServer` implementation.
MBeanServerDelegate	Represents the MBean server from the management point of view.
MBeanServerFactory	Provides MBean server references.
MBeanServerInvocationHandler	`InvocationHandler` that forwards methods in an MBean's management interface through the MBean server to the MBean.
MBeanServerNotification	Represents a notification emitted by the MBean server through the MBeanServerDelegate MBean.
MBeanServerPermission	A Permission to perform actions related to MBeanServers.
MBeanTrustPermission	This permission represents "trust" in a signer or codebase.
Notification	The Notification class represents a notification emitted by an MBean.
NotificationBroadcasterSupport	Provides an implementation of `NotificationEmitter` interface.
NotificationFilterSupport	Provides an implementation of the `NotificationFilter` interface.
ObjectInstance	Used to represent the object name of an MBean and its class name.
ObjectName	Represents the object name of an MBean, or a pattern that can match the names of several MBeans.
Query	Constructs query object constraints.
QueryEval	Allows a query to be performed in the context of a specific MBean server.
StandardMBean	An MBean whose management interface is determined by reflection on a Java interface.
StringValueExp	Represents strings that are arguments to relational constraints.

Exception Summary
AttributeNotFoundException	The specified attribute does not exist or cannot be retrieved.
BadAttributeValueExpException	Thrown when an invalid MBean attribute is passed to a query constructing method.
BadBinaryOpValueExpException	Thrown when an invalid expression is passed to a method for constructing a query.
BadStringOperationException	Thrown when an invalid string operation is passed to a method for constructing a query.
InstanceAlreadyExistsException	The MBean is already registered in the repository.
InstanceNotFoundException	The specified MBean does not exist in the repository.
IntrospectionException	An exception occurred during the introspection of an MBean.
InvalidApplicationException	Thrown when an attempt is made to apply either of the following: A subquery expression to an MBean or a qualified attribute expression to an MBean of the wrong class.
InvalidAttributeValueException	The value specified is not valid for the attribute.
JMException	Exceptions thrown by JMX implementations.
JMRuntimeException	Runtime exceptions emitted by JMX implementations.
ListenerNotFoundException	The specified MBean listener does not exist in the repository.
MalformedObjectNameException	The format of the string does not correspond to a valid ObjectName.
MBeanException	Represents "user defined" exceptions thrown by MBean methods in the agent.
MBeanRegistrationException	Wraps exceptions thrown by the preRegister(), preDeregister() methods of the `MBeanRegistration` interface.
NotCompliantMBeanException	Exception which occurs when trying to register an object in the MBean server that is not a JMX compliant MBean.
OperationsException	Represents exceptions thrown in the MBean server when performing operations on MBeans.
ReflectionException	Represents exceptions thrown in the MBean server when using the java.lang.reflect classes to invoke methods on MBeans.
RuntimeErrorException	When a `java.lang.Error` occurs in the agent it should be caught and re-thrown as a `RuntimeErrorException`.
RuntimeMBeanException	Represents runtime exceptions thrown by MBean methods in the agent.
RuntimeOperationsException	Represents runtime exceptions thrown in the agent when performing operations on MBeans.
ServiceNotFoundException	Represents exceptions raised when a requested service is not supported.

Package javax.management Description

Provides the core classes for the Java Management Extensions.

The Java Management Extensions (JMX^TM) API is a standard API for management and monitoring. Typical uses include:

consulting and changing application configuration
accumulating statistics about application behavior and making them available
notifying of state changes and erroneous conditions.

The JMX API can also be used as part of a solution for managing systems, networks, and so on.

The API includes remote access, so a remote management program can interact with a running application for these purposes.

MBeans

The fundamental notion of the JMX API is the MBean. An MBean is a named managed object representing a resource. It has a management interface consisting of:

named and typed attributes that can be read and/or written
named and typed operations that can be invoked
typed notifications that can be emitted by the MBean.

For example, an MBean representing an application's configuration could have attributes representing the different configuration items. Reading the CacheSize attribute would return the current value of that item. Writing it would update the item, potentially changing the behavior of the running application. An operation such as save could store the current configuration persistently. A notification such as ConfigurationChangedNotification could be sent every time the configuration is changed.

In the standard usage of the JMX API, MBeans are implemented as Java objects. However, as explained below, these objects are not usually referenced directly.

Standard MBeans

To make MBean implementation simple, the JMX API includes the notion of Standard MBeans. A Standard MBean is one whose attributes and operations are deduced from a Java interface using certain naming patterns, similar to those used by JavaBeans^TM. For example, consider an interface like this:

    public interface ConfigurationMBean {
        public int getCacheSize();
        public void setCacheSize(int size);
        public long getLastChangedTime();
        public void save();
    }

The methods getCacheSize and setCacheSize define a read-write attribute of type int called CacheSize (with an initial capital, unlike the JavaBeans convention).

The method getLastChangedTime defines an attribute of type long called LastChangedTime. This is a read-only attribute, since there is no method setLastChangedTime.

The method save defines an operation called save. It is not an attribute, since its name does not begin with get, set, or is.

The exact naming patterns for Standard MBeans are detailed in the JMX Specification.

There are two ways to make a Java object that is an MBean with this management interface. One is for the object to be of a class that has exactly the same name as the Java interface but without the MBean suffix. So in the example the object would be of the class Configuration, in the same Java package as ConfigurationMBean. The second way is to use the StandardMBean class.

Dynamic MBeans

A Dynamic MBean is an MBean that defines its management interface at run-time. For example, a configuration MBean could determine the names and types of the attributes it exposes by parsing an XML file.

Any Java object of a class that implements the DynamicMBean interface is a Dynamic MBean.

Open MBeans

An Open MBean is a kind of Dynamic MBean where the types of attributes and of operation parameters and return values are built using a small set of predefined Java classes. Open MBeans facilitate operation with remote management programs that do not necessarily have access to application-specific types, including non-Java programs. Open MBeans are defined by the package javax.management.openmbean.

Model MBeans

A Model MBean is a kind of Dynamic MBean that acts as a bridge between the management interface and the underlying managed resource. Both the management interface and the managed resource are specified as Java objects. The same Model MBean implementation can be reused many times with different management interfaces and managed resources, and it can provide common functionality such as persistence and caching. Model MBeans are defined by the package javax.management.modelmbean.

MBean Server

To be useful, an MBean must be registered in an MBean Server. An MBean Server is a repository of MBeans. Usually the only access to the MBeans is through the MBean Server. In other words, code no longer accesses the Java object implementing the MBean directly, but instead accesses the MBean by name through the MBean Server. Each MBean has a unique name within the MBean Server, defined by the ObjectName class.

An MBean Server is an object implementing the interface MBeanServer. As of J2SE 1.5, a Platform MBean Server is available. This is a single MBean Server that can be shared by different managed components running within the same Java Virtual Machine. The Platform MBean Server is accessed with the method ManagementFactory.getPlatformMBeanServer().

Application code can also create a new MBean Server, or access already-created MBean Servers, using the MBeanServerFactory class.

Creating MBeans in the MBean Server

There are two ways to create an MBean. One is to construct a Java object that will be the MBean, then use the registerMBean method to register it in the MBean Server. The other is to create and register the MBean in a single operation using one of the createMBean methods.

The registerMBean method is simpler for local use, but cannot be used remotely. The createMBean method can be used remotely, but sometimes requires attention to class loading issues.

An MBean can perform actions when it is registered in or unregistered from an MBean Server if it implements the MBeanRegistration interface.

Accessing MBeans in the MBean Server

Given an ObjectName name and an MBeanServer mbs, you can access attributes and operations as in this example:

    int cacheSize = mbs.getAttribute(name, "CacheSize");
    Attribute newCacheSize =
        new Attribute("CacheSize", new Integer(2000));
    mbs.setAttribute(name, newCacheSize);
    mbs.invoke(name, "save", new Object[0], new Class[0]);

Alternatively, if you have a Java interface that corresponds to the management interface for the MBean, you can use an MBean proxy like this:

    ConfigurationMBean conf = (ConfigurationMBean)
        MBeanServerInvocationHandler.newProxyInstance(mbs,
                                                      name,
                                                      ConfigurationMBean.class,
                                                      false);
    int cacheSize = conf.getCacheSize();
    conf.setCacheSize(2000);
    conf.save();

Using an MBean proxy is just a convenience. The second example ends up calling the same MBeanServer operations as the first one.

An MBean Server can be queried for MBeans whose names match certain patterns and/or whose attributes meet certain constraints. Name patterns are constructed using the ObjectName class and constraints are constructed using the Query class. The methods queryNames and queryMBeans then perform the query.

Notifications

A notification is an instance of the Notification class or a subclass. In addition to its Java class, it has a type string that can distinguish it from other notifications of the same class.

An MBean that will emit notifications must implement the NotificationBroadcaster or NotificationEmitter interface. Usually, it does this by subclassing NotificationBroadcasterSupport or by delegating to an instance of that class.

Notifications can be received by a listener, which is an object that implements the NotificationListener interface. You can add a listener to an MBean with the method MBeanServer.addNotificationListener(ObjectName, NotificationListener, NotificationFilter, Object). You can optionally supply a filter to this method, to select only notifications of interest. A filter is an object that implements the NotificationFilter interface.

An MBean can be a listener for notifications emitted by other MBeans in the same MBean Server. In this case, it implements NotificationListener and the method MBeanServer.addNotificationListener(ObjectName, ObjectName, NotificationFilter, Object) is used to listen.

Remote Access to MBeans

An MBean Server can be accessed remotely through a connector. A connector allows a remote Java application to access an MBean Server in essentially the same way as a local one. The package javax.management.remote defines connectors.

The JMX specification also defines the notion of an adaptor. An adaptor translates between requests in a protocol such as SNMP or HTML and accesses to an MBean Server. So for example an SNMP GET operation might result in a getAttribute on the MBean Server.

Package Specification

Specification of the JMX API, version 1.2

Since:: 1.5