Module java.management
Package javax.management.modelmbean

Class RequiredModelMBean

  • All Implemented Interfaces:
    DynamicMBean, MBeanRegistration, ModelMBean, ModelMBeanNotificationBroadcaster, NotificationBroadcaster, NotificationEmitter, PersistentMBean
    public class RequiredModelMBean
extends Object
implements ModelMBean, MBeanRegistration, NotificationEmitter
    This class is the implementation of a ModelMBean. An appropriate implementation of a ModelMBean must be shipped with every JMX Agent and the class must be named RequiredModelMBean.

    Java resources wishing to be manageable instantiate the RequiredModelMBean using the MBeanServer's createMBean method. The resource then sets the MBeanInfo and Descriptors for the RequiredModelMBean instance. The attributes and operations exposed via the ModelMBeanInfo for the ModelMBean are accessible from MBeans, connectors/adaptors like other MBeans. Through the Descriptors, values and methods in the managed application can be defined and mapped to attributes and operations of the ModelMBean. This mapping can be defined in an XML formatted file or dynamically and programmatically at runtime.

    Every RequiredModelMBean which is instantiated in the MBeanServer becomes manageable:
    its attributes and operations become remotely accessible through the connectors/adaptors connected to that MBeanServer.

    A Java object cannot be registered in the MBeanServer unless it is a JMX compliant MBean. By instantiating a RequiredModelMBean, resources are guaranteed that the MBean is valid. MBeanException and RuntimeOperationsException must be thrown on every public method. This allows for wrapping exceptions from distributed communications (RMI, EJB, etc.)

    Since:
    1.5

    • Method Detail

      • store

        public void store()
           throws MBeanException,
                  RuntimeOperationsException,
                  InstanceNotFoundException

        Captures the current state of this MBean instance and writes it out to the persistent store. The state stored could include attribute and operation values.

        If the implementation of this class does not support persistence, an MBeanException wrapping a ServiceNotFoundException is thrown.

        Persistence policy from the MBean and attribute descriptor is used to guide execution of this method. The MBean should be stored if 'persistPolicy' field is:

         != "never"
   = "always"
   = "onTimer" and now > 'lastPersistTime' + 'persistPeriod'
   = "NoMoreOftenThan" and now > 'lastPersistTime' + 'persistPeriod'
   = "onUnregister"

        Do not store the MBean if 'persistPolicy' field is:

            = "never"
    = "onUpdate"
    = "onTimer" && now < 'lastPersistTime' + 'persistPeriod'
        Specified by:
        store in interface PersistentMBean
        Throws:
        MBeanException - Wraps another exception, or persistence is not supported
        RuntimeOperationsException - Wraps exceptions from the persistence mechanism
        InstanceNotFoundException - Could not find/access the persistent store

      • getMBeanInfo

        public MBeanInfo getMBeanInfo()
        Returns the attributes, operations, constructors and notifications that this RequiredModelMBean exposes for management.
        Specified by:
        getMBeanInfo in interface DynamicMBean
        Returns:
        An instance of ModelMBeanInfo allowing retrieval all attributes, operations, and Notifications of this MBean.

      • invoke

        public Object invoke​(String opName,
                     Object[] opArgs,
                     String[] sig)
              throws MBeanException,
                     ReflectionException
        Invokes a method on or through a RequiredModelMBean and returns the result of the method execution.

        If the given method to be invoked, together with the provided signature, matches one of RequiredModelMbean accessible methods, this one will be call. Otherwise the call to the given method will be tried on the managed resource.

        The last value returned by an operation may be cached in the operation's descriptor which is in the ModelMBeanOperationInfo's descriptor. The valid value will be in the 'value' field if there is one. If the 'currencyTimeLimit' field in the descriptor is:

        • <0 Then the value is not cached and is never valid. The operation method is invoked. The 'value' and 'lastUpdatedTimeStamp' fields are cleared.
        • =0 Then the value is always cached and always valid. The 'value' field is returned. If there is no 'value' field then the operation method is invoked for the attribute. The 'lastUpdatedTimeStamp' field and `value' fields are set to the operation's return value and the current time stamp.
        • >0 Represents the number of seconds that the 'value' field is valid. The 'value' field is no longer valid when 'lastUpdatedTimeStamp' + 'currencyTimeLimit' > Now.
          • When 'value' is valid, 'value' is returned.
          • When 'value' is no longer valid then the operation method is invoked. The 'lastUpdatedTimeStamp' field and `value' fields are updated.

        Note: because of inconsistencies in previous versions of this specification, it is recommended not to use negative or zero values for currencyTimeLimit. To indicate that a cached value is never valid, omit the currencyTimeLimit field. To indicate that it is always valid, use a very large number for this field.

        Specified by:
        invoke in interface DynamicMBean
        Parameters:
        opName - The name of the method to be invoked. The name can be the fully qualified method name including the classname, or just the method name if the classname is defined in the 'class' field of the operation descriptor.
        opArgs - An array containing the parameters to be set when the operation is invoked
        sig - An array containing the signature of the operation. The class objects will be loaded using the same class loader as the one used for loading the MBean on which the operation was invoked.
        Returns:
        The object returned by the method, which represents the result of invoking the method on the specified managed resource.
        Throws:
        MBeanException - Wraps one of the following Exceptions:
        • An Exception thrown by the managed object's invoked method.
        • ServiceNotFoundException: No ModelMBeanOperationInfo or no descriptor defined for the specified operation or the managed resource is null.
        • InvalidTargetObjectTypeException: The 'targetType' field value is not 'objectReference'.
        ReflectionException - Wraps an Exception thrown while trying to invoke the method.
        RuntimeOperationsException - Wraps an IllegalArgumentException Method name is null.

      • getAttribute

        public Object getAttribute​(String attrName)
                    throws AttributeNotFoundException,
                           MBeanException,
                           ReflectionException
        Returns the value of a specific attribute defined for this ModelMBean. The last value returned by an attribute may be cached in the attribute's descriptor. The valid value will be in the 'value' field if there is one. If the 'currencyTimeLimit' field in the descriptor is:
        • <0 Then the value is not cached and is never valid. The getter method is invoked for the attribute. The 'value' and 'lastUpdatedTimeStamp' fields are cleared.
        • =0 Then the value is always cached and always valid. The 'value' field is returned. If there is no'value' field then the getter method is invoked for the attribute. The 'lastUpdatedTimeStamp' field and `value' fields are set to the attribute's value and the current time stamp.
        • >0 Represents the number of seconds that the 'value' field is valid. The 'value' field is no longer valid when 'lastUpdatedTimeStamp' + 'currencyTimeLimit' > Now.
          • When 'value' is valid, 'value' is returned.
          • When 'value' is no longer valid then the getter method is invoked for the attribute. The 'lastUpdatedTimeStamp' field and `value' fields are updated.

        Note: because of inconsistencies in previous versions of this specification, it is recommended not to use negative or zero values for currencyTimeLimit. To indicate that a cached value is never valid, omit the currencyTimeLimit field. To indicate that it is always valid, use a very large number for this field.

        If the 'getMethod' field contains the name of a valid operation descriptor, then the method described by the operation descriptor is executed. The response from the method is returned as the value of the attribute. If the operation fails or the returned value is not compatible with the declared type of the attribute, an exception will be thrown.

        If no 'getMethod' field is defined then the default value of the attribute is returned. If the returned value is not compatible with the declared type of the attribute, an exception will be thrown.

        The declared type of the attribute is the String returned by MBeanAttributeInfo.getType(). A value is compatible with this type if one of the following is true:

        • the value is null;
        • the declared name is a primitive type name (such as "int") and the value is an instance of the corresponding wrapper type (such as java.lang.Integer);
        • the name of the value's class is identical to the declared name;
        • the declared name can be loaded by the value's class loader and produces a class to which the value can be assigned.

        In this implementation, in every case where the getMethod needs to be called, because the method is invoked through the standard "invoke" method and thus needs operationInfo, an operation must be specified for that getMethod so that the invocation works correctly.

        Specified by:
        getAttribute in interface DynamicMBean
        Parameters:
        attrName - A String specifying the name of the attribute to be retrieved. It must match the name of a ModelMBeanAttributeInfo.
        Returns:
        The value of the retrieved attribute from the descriptor 'value' field or from the invocation of the operation in the 'getMethod' field of the descriptor.
        Throws:
        AttributeNotFoundException - The specified attribute is not accessible in the MBean. The following cases may result in an AttributeNotFoundException:
        • No ModelMBeanInfo was found for the Model MBean.
        • No ModelMBeanAttributeInfo was found for the specified attribute name.
        • The ModelMBeanAttributeInfo isReadable method returns 'false'.
        MBeanException - Wraps one of the following Exceptions:
        • InvalidAttributeValueException: A wrong value type was received from the attribute's getter method or no 'getMethod' field defined in the descriptor for the attribute and no default value exists.
        • ServiceNotFoundException: No ModelMBeanOperationInfo defined for the attribute's getter method or no descriptor associated with the ModelMBeanOperationInfo or the managed resource is null.
        • InvalidTargetObjectTypeException The 'targetType' field value is not 'objectReference'.
        • An Exception thrown by the managed object's getter.
        ReflectionException - Wraps an Exception thrown while trying to invoke the getter.
        RuntimeOperationsException - Wraps an IllegalArgumentException: The attribute name in parameter is null.
        See Also:
        setAttribute(javax.management.Attribute)

      • setAttribute

        public void setAttribute​(Attribute attribute)
                  throws AttributeNotFoundException,
                         InvalidAttributeValueException,
                         MBeanException,
                         ReflectionException
        Sets the value of a specific attribute of a named ModelMBean. If the 'setMethod' field of the attribute's descriptor contains the name of a valid operation descriptor, then the method described by the operation descriptor is executed. In this implementation, the operation descriptor must be specified correctly and assigned to the modelMBeanInfo so that the 'setMethod' works correctly. The response from the method is set as the value of the attribute in the descriptor.

        If currencyTimeLimit is > 0, then the new value for the attribute is cached in the attribute descriptor's 'value' field and the 'lastUpdatedTimeStamp' field is set to the current time stamp.

        If the persist field of the attribute's descriptor is not null then Persistence policy from the attribute descriptor is used to guide storing the attribute in a persistent store.
        Store the MBean if 'persistPolicy' field is:

        • != "never"
        • = "always"
        • = "onUpdate"
        • = "onTimer" and now > 'lastPersistTime' + 'persistPeriod'
        • = "NoMoreOftenThan" and now > 'lastPersistTime' + 'persistPeriod'
        Do not store the MBean if 'persistPolicy' field is:
        • = "never"
        • = = "onTimer" && now < 'lastPersistTime' + 'persistPeriod'
        • = "onUnregister"
        • = = "NoMoreOftenThan" and now < 'lastPersistTime' + 'persistPeriod'

        The ModelMBeanInfo of the Model MBean is stored in a file.

        Specified by:
        setAttribute in interface DynamicMBean
        Parameters:
        attribute - The Attribute instance containing the name of the attribute to be set and the value it is to be set to.
        Throws:
        AttributeNotFoundException - The specified attribute is not accessible in the MBean.
        The following cases may result in an AttributeNotFoundException:
        • No ModelMBeanAttributeInfo is found for the specified attribute.
        • The ModelMBeanAttributeInfo's isWritable method returns 'false'.
        InvalidAttributeValueException - No descriptor is defined for the specified attribute.
        MBeanException - Wraps one of the following Exceptions:
        • An Exception thrown by the managed object's setter.
        • A ServiceNotFoundException if a setMethod field is defined in the descriptor for the attribute and the managed resource is null; or if no setMethod field is defined and caching is not enabled for the attribute. Note that if there is no getMethod field either, then caching is automatically enabled.
        • InvalidTargetObjectTypeException The 'targetType' field value is not 'objectReference'.
        • An Exception thrown by the managed object's getter.
        ReflectionException - Wraps an Exception thrown while trying to invoke the setter.
        RuntimeOperationsException - Wraps an IllegalArgumentException: The attribute in parameter is null.
        See Also:
        getAttribute(java.lang.String)

      • setAttributes

        public AttributeList setAttributes​(AttributeList attributes)
        Sets the values of an array of attributes of this ModelMBean. Executes the setAttribute() method for each attribute in the list.
        Specified by:
        setAttributes in interface DynamicMBean
        Parameters:
        attributes - A list of attributes: The identification of the attributes to be set and the values they are to be set to.
        Returns:
        The array of attributes that were set, with their new values in Attribute instances.
        Throws:
        RuntimeOperationsException - Wraps an IllegalArgumentException: The object name in parameter is null or attributes in parameter is null.
        See Also:
        getAttributes(java.lang.String[])

      • getNotificationInfo

        public MBeanNotificationInfo[] getNotificationInfo()
        Returns the array of Notifications always generated by the RequiredModelMBean.

        RequiredModelMBean may always send also two additional notifications:

        • One with descriptor "name=GENERIC,descriptorType=notification,log=T,severity=6,displayName=jmx.modelmbean.generic"
        • Second is a standard attribute change notification with descriptor "name=ATTRIBUTE_CHANGE,descriptorType=notification,log=T,severity=6,displayName=jmx.attribute.change"
        Thus these two notifications are always added to those specified by the application.
        Specified by:
        getNotificationInfo in interface NotificationBroadcaster
        Returns:
        MBeanNotificationInfo[]

      • getClassLoaderRepository

        protected ClassLoaderRepository getClassLoaderRepository()
        Return the Class Loader Repository used to perform class loading. Subclasses may wish to redefine this method in order to return the appropriate ClassLoaderRepository that should be used in this object.
        Returns:
        the Class Loader Repository.

      • preRegister

        public ObjectName preRegister​(MBeanServer server,
                              ObjectName name)
                       throws Exception
        Allows the MBean to perform any operations it needs before being registered in the MBean server. If the name of the MBean is not specified, the MBean can provide a name for its registration. If any exception is raised, the MBean will not be registered in the MBean server.

        In order to ensure proper run-time semantics of RequireModelMBean, Any subclass of RequiredModelMBean overloading or overriding this method should call super.preRegister(server, name) in its own preRegister implementation.

        Specified by:
        preRegister in interface MBeanRegistration
        Parameters:
        server - The MBean server in which the MBean will be registered.
        name - The object name of the MBean. This name is null if the name parameter to one of the createMBean or registerMBean methods in the MBeanServer interface is null. In that case, this method must return a non-null ObjectName for the new MBean.
        Returns:
        The name under which the MBean is to be registered. This value must not be null. If the name parameter is not null, it will usually but not necessarily be the returned value.
        Throws:
        Exception - This exception will be caught by the MBean server and re-thrown as an MBeanRegistrationException.

      • postRegister

        public void postRegister​(Boolean registrationDone)
        Allows the MBean to perform any operations needed after having been registered in the MBean server or after the registration has failed.

        In order to ensure proper run-time semantics of RequireModelMBean, Any subclass of RequiredModelMBean overloading or overriding this method should call super.postRegister(registrationDone) in its own postRegister implementation.

        Specified by:
        postRegister in interface MBeanRegistration
        Parameters:
        registrationDone - Indicates whether or not the MBean has been successfully registered in the MBean server. The value false means that the registration phase has failed.

      • preDeregister

        public void preDeregister()
                   throws Exception
        Allows the MBean to perform any operations it needs before being unregistered by the MBean server.

        In order to ensure proper run-time semantics of RequireModelMBean, Any subclass of RequiredModelMBean overloading or overriding this method should call super.preDeregister() in its own preDeregister implementation.

        Specified by:
        preDeregister in interface MBeanRegistration
        Throws:
        Exception - This exception will be caught by the MBean server and re-thrown as an MBeanRegistrationException.

      • postDeregister

        public void postDeregister()
        Allows the MBean to perform any operations needed after having been unregistered in the MBean server.

        In order to ensure proper run-time semantics of RequireModelMBean, Any subclass of RequiredModelMBean overloading or overriding this method should call super.postDeregister() in its own postDeregister implementation.

        Specified by:
        postDeregister in interface MBeanRegistration