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Java Dynamic Management Kit 5.1 Tutorial

2.2.2 getMBeanInfo Method

Because the MBean description should never change, it is usually created one time only at instantiation, and the getMBeanInfo method simply returns its reference at every call. The MBean constructor should therefore build the MBeanInfo object from the MBean metadata classes such that it accurately describes the management interface. And since most dynamic MBeans will always be instantiated with the same management interface, building the MBeanInfo object is fairly straightforward.

Example 2–2 shows how the SimpleDynamic MBean defines its management interface, as built at instantiation and returned by its getMBeanInfo method.

Example 2–2 Implementation of the getMBeanInfo Method

    private void buildDynamicMBeanInfo() {

        dAttributes[0] =
            new MBeanAttributeInfo("State",
                                   "java.lang.String",
                                   "State string.",
                                   true,
                                   true,
                                   false);
        dAttributes[1] =
            new MBeanAttributeInfo("NbChanges",
                                   "java.lang.Integer",
                                   "Number of times the " +
                                   "State string has been changed.",
                                   true,
                                   false,
                                   false);

        Constructor[] constructors = this.getClass().getConstructors();
        dConstructors[0] =
            new MBeanConstructorInfo("Constructs a " +
                                     "SimpleDynamic object",
                                     constructors[0]);

        MBeanParameterInfo[] params = null;
        dOperations[0] =
            new MBeanOperationInfo("reset",
                                   "reset State and NbChanges " +
                                   "attributes to their initial values",
                                   params , 
                                   "void", 
                                   MBeanOperationInfo.ACTION);

        dNotifications[0] =
            new MBeanNotificationInfo(
            new String[] { AttributeChangeNotification.ATTRIBUTE_CHANGE },
            AttributeChangeNotification.class.getName(),
            "This notification is emitted when the reset() method 
            is called.");

        dMBeanInfo = new MBeanInfo(dClassName,
                                   dDescription,
                                   dAttributes,
                                   dConstructors,
                                   dOperations,
                                   dNotifications);
    }
// PRIVATE VARIABLES

    private MBeanAttributeInfo[] dAttributes =
        new MBeanAttributeInfo[2];
    private MBeanConstructorInfo[] dConstructors =
        new MBeanConstructorInfo[1];
    private MBeanNotificationInfo[] dNotifications =
        new MBeanNotificationInfo[1];
    private MBeanOperationInfo[] dOperations =
        new MBeanOperationInfo[1];
    private MBeanInfo dMBeanInfo = null;
}