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java.rmi.activation
abstract public class: ActivationGroup [javadoc | source]
java.lang.Object
   java.rmi.server.RemoteObject
      java.rmi.server.RemoteServer
         java.rmi.server.UnicastRemoteObject
            java.rmi.activation.ActivationGroup

All Implemented Interfaces:
    ActivationInstantiator, Remote, Serializable

An ActivationGroup is responsible for creating new instances of "activatable" objects in its group, informing its ActivationMonitor when either: its object's become active or inactive, or the group as a whole becomes inactive.

An ActivationGroup is initially created in one of several ways:

Only the activator can recreate an ActivationGroup. The activator spawns, as needed, a separate VM (as a child process, for example) for each registered activation group and directs activation requests to the appropriate group. It is implementation specific how VMs are spawned. An activation group is created via the ActivationGroup.createGroup static method. The createGroup method has two requirements on the group to be created: 1) the group must be a concrete subclass of ActivationGroup, and 2) the group must have a constructor that takes two arguments:

When created, the default implementation of ActivationGroup will override the system properties with the properties requested when its ActivationGroupDesc was created, and will set a java.rmi.RMISecurityManager as the default system security manager. If your application requires specific properties to be set when objects are activated in the group, the application should create a special Properties object containing these properties, then create an ActivationGroupDesc with the Properties object, and use ActivationGroup.createGroup before creating any ActivationDescs (before the default ActivationGroupDesc is created). If your application requires the use of a security manager other than java.rmi.RMISecurityManager, in the ActivativationGroupDescriptor properties list you can set java.security.manager property to the name of the security manager you would like to install.

Fields inherited from java.rmi.server.RemoteObject:
ref
Constructor:
 protected ActivationGroup(ActivationGroupID groupID) throws RemoteException 
    Constructs an activation group with the given activation group identifier. The group is exported as a java.rmi.server.UnicastRemoteObject.
    Parameters:
    groupID - the group's identifier
    Throws:
    RemoteException - if this group could not be exported
    since: 1.2 -
Method from java.rmi.activation.ActivationGroup Summary:
activeObject,   activeObject,   createGroup,   currentGroup,   currentGroupID,   getSystem,   inactiveGroup,   inactiveObject,   internalCurrentGroupID,   setSystem
Methods from java.rmi.server.UnicastRemoteObject:
clone,   exportObject,   exportObject,   exportObject,   unexportObject
Methods from java.rmi.server.RemoteServer:
getClientHost,   getLog,   setLog
Methods from java.rmi.server.RemoteObject:
equals,   getRef,   hashCode,   toString,   toStub
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from java.rmi.activation.ActivationGroup Detail:
 abstract public  void activeObject(ActivationID id,
    Remote obj) throws ActivationException, UnknownObjectException, RemoteException
    The group's activeObject method is called when an object is exported (either by Activatable object construction or an explicit call to Activatable.exportObject. The group must inform its ActivationMonitor that the object is active (via the monitor's activeObject method) if the group hasn't already done so.
 protected  void activeObject(ActivationID id,
    MarshalledObject<Remote> mobj) throws ActivationException, UnknownObjectException, RemoteException 
    This protected method is necessary for subclasses to make the activeObject callback to the group's monitor. The call is simply forwarded to the group's ActivationMonitor.
 public static synchronized ActivationGroup createGroup(ActivationGroupID id,
    ActivationGroupDesc desc,
    long incarnation) throws ActivationException 
    Create and set the activation group for the current VM. The activation group can only be set if it is not currently set. An activation group is set using the createGroup method when the Activator initiates the re-creation of an activation group in order to carry out incoming activate requests. A group must first be registered with the ActivationSystem before it can be created via this method.

    The group class specified by the ActivationGroupDesc must be a concrete subclass of ActivationGroup and have a public constructor that takes two arguments: the ActivationGroupID for the group and the MarshalledObject containing the group's initialization data (obtained from the ActivationGroupDesc.

    If the group class name specified in the ActivationGroupDesc is null, then this method will behave as if the group descriptor contained the name of the default activation group implementation class.

    Note that if your application creates its own custom activation group, a security manager must be set for that group. Otherwise objects cannot be activated in the group. java.rmi.RMISecurityManager is set by default.

    If a security manager is already set in the group VM, this method first calls the security manager's checkSetFactory method. This could result in a SecurityException. If your application needs to set a different security manager, you must ensure that the policy file specified by the group's ActivationGroupDesc grants the group the necessary permissions to set a new security manager. (Note: This will be necessary if your group downloads and sets a security manager).

    After the group is created, the ActivationSystem is informed that the group is active by calling the activeGroup method which returns the ActivationMonitor for the group. The application need not call activeGroup independently since it is taken care of by this method.

    Once a group is created, subsequent calls to the currentGroupID method will return the identifier for this group until the group becomes inactive.

 static synchronized ActivationGroup currentGroup() throws ActivationException 
    Returns the current group for the VM.
 public static synchronized ActivationGroupID currentGroupID() 
    Returns the current activation group's identifier. Returns null if no group is currently active for this VM.
 public static synchronized ActivationSystem getSystem() throws ActivationException 
    Returns the activation system for the VM. The activation system may be set by the setSystem method. If the activation system is not set via the setSystem method, then the getSystem method attempts to obtain a reference to the ActivationSystem by looking up the name "java.rmi.activation.ActivationSystem" in the Activator's registry. By default, the port number used to look up the activation system is defined by ActivationSystem.SYSTEM_PORT. This port can be overridden by setting the property java.rmi.activation.port.
 protected  void inactiveGroup() throws UnknownGroupException, RemoteException 
    This protected method is necessary for subclasses to make the inactiveGroup callback to the group's monitor. The call is simply forwarded to the group's ActivationMonitor. Also, the current group for the VM is set to null.
 public boolean inactiveObject(ActivationID id) throws ActivationException, UnknownObjectException, RemoteException 
    The group's inactiveObject method is called indirectly via a call to the Activatable.inactive method. A remote object implementation must call Activatable's inactive method when that object deactivates (the object deems that it is no longer active). If the object does not call Activatable.inactive when it deactivates, the object will never be garbage collected since the group keeps strong references to the objects it creates.

    The group's inactiveObject method unexports the remote object from the RMI runtime so that the object can no longer receive incoming RMI calls. An object will only be unexported if the object has no pending or executing calls. The subclass of ActivationGroup must override this method and unexport the object.

    After removing the object from the RMI runtime, the group must inform its ActivationMonitor (via the monitor's inactiveObject method) that the remote object is not currently active so that the remote object will be re-activated by the activator upon a subsequent activation request.

    This method simply informs the group's monitor that the object is inactive. It is up to the concrete subclass of ActivationGroup to fulfill the additional requirement of unexporting the object.

 static synchronized ActivationGroupID internalCurrentGroupID() throws ActivationException 
    Returns the activation group identifier for the VM. If an activation group does not exist for this VM, a default activation group is created. A group can be created only once, so if a group has already become active and deactivated.
 public static synchronized  void setSystem(ActivationSystem system) throws ActivationException 
    Set the activation system for the VM. The activation system can only be set it if no group is currently active. If the activation system is not set via this call, then the getSystem method attempts to obtain a reference to the ActivationSystem by looking up the name "java.rmi.activation.ActivationSystem" in the Activator's registry. By default, the port number used to look up the activation system is defined by ActivationSystem.SYSTEM_PORT. This port can be overridden by setting the property java.rmi.activation.port.

    If there is a security manager, this method first calls the security manager's checkSetFactory method. This could result in a SecurityException.