javax.management.modelmbean (Java SE 26 & JDK 26)
Description: declaration: module: java.management, package: javax.management.modelmbean
Keywords: javax.management.modelmbean package

# Package javax.management.modelmbean

package javax.management.modelmbean

Provides the definition of the ModelMBean classes. A Model MBean is an 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.

A Model MBean implements the `ModelMBean` interface. It is a `DynamicMBean` whose `getMBeanInfo` method returns an object implementing `ModelMBeanInfo`.

Every MBean has an `MBeanInfo` with information about the MBean itself, and its attributes, operations, constructors, and notifications. A Model MBean augments this `MBeanInfo` with `Descriptor`s that encode additional information in the form of (key,value) pairs. Usually, `Descriptor`s are instances of `DescriptorSupport`.

The class `RequiredModelMBean` provides a standard Model MBean implementation.

The following example shows a Model MBean being used to make the `get` method of a `HashMap` available for management through an MBean server. No other methods are available through the MBean server. There is nothing special about `HashMap` here. Public methods from any public class can be exposed for management in the same way.

    import java.lang.reflect.Method;
    import java.util.HashMap;
    import javax.management.*;
    import javax.management.modelmbean.*;

    // ...

    MBeanServer mbs = MBeanServerFactory.createMBeanServer();
    // The MBean Server

    HashMap map = new HashMap();
    // The resource that will be managed

    // Construct the management interface for the Model MBean
    Method getMethod = HashMap.class.getMethod("get", new Class[] {Object.class});
    ModelMBeanOperationInfo getInfo =
        new ModelMBeanOperationInfo("Get value for key", getMethod);
    ModelMBeanInfo mmbi =
        new ModelMBeanInfoSupport(HashMap.class.getName(),
                      "Map of keys and values",
                      null,  // no attributes
                      null,  // no constructors
                      new ModelMBeanOperationInfo[] {getInfo},
                      null); // no notifications

    // Make the Model MBean and link it to the resource
    ModelMBean mmb = new RequiredModelMBean(mmbi);
    mmb.setManagedResource(map, "ObjectReference");

    // Register the Model MBean in the MBean Server
    ObjectName mapName = new ObjectName(":type=Map,name=whatever");
    mbs.registerMBean(mmb, mapName);

    // Resource can evolve independently of the MBean
    map.put("key", "value");

    // Can access the "get" method through the MBean Server
    mbs.invoke(mapName, "get", new Object[] {"key"}, new String[] {Object.class.getName()});
    // returns "value"

## Package Specification

- See the JMX 1.4 Specification JMX Specification, version 1.4

Since:
  1.5

- Related Packages
  Package
  Description
  javax.management
  Provides the core classes for the Java Management Extensions.
- Class
  Description
  DescriptorSupport
  This class represents the metadata set for a ModelMBean element.
  InvalidTargetObjectTypeException
  Exception thrown when an invalid target object type is specified.
  ModelMBean
  This interface must be implemented by the ModelMBeans.
  ModelMBeanAttributeInfo
  The ModelMBeanAttributeInfo object describes an attribute of the ModelMBean.
  ModelMBeanConstructorInfo
  The ModelMBeanConstructorInfo object describes a constructor of the ModelMBean.
  ModelMBeanInfo
  This interface is implemented by the ModelMBeanInfo for every ModelMBean.
  ModelMBeanInfoSupport
  This class represents the meta data for ModelMBeans.
  ModelMBeanNotificationBroadcaster
  This interface must be implemented by the ModelMBeans.
  ModelMBeanNotificationInfo
  The ModelMBeanNotificationInfo object describes a notification emitted by a ModelMBean.
  ModelMBeanOperationInfo
  The ModelMBeanOperationInfo object describes a management operation of the ModelMBean.
  RequiredModelMBean
  This class is the implementation of a ModelMBean.