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Class java.rmi.activation.ActivationGroup

java.lang.Object
    |
    +----java.rmi.server.RemoteObject
            |
            +----java.rmi.server.RemoteServer
                    |
                    +----java.rmi.server.UnicastRemoteObject
                            |
                            +----java.rmi.activation.ActivationGroup

public abstract class ActivationGroup
extends UnicastRemoteObject
implements ActivationInstantiator

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:

as a side-effect of creating a "default" ActivationDesc for an object, or
via the ActivationGroup.createGroup method
as a side-effect of activating the first object in a group whose ActivationGroupDesc was only registered.
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:
- the group's ActivationGroupID, and
- the group's initialization data (in a java.rmi.MarshalledObject)
When created, the default implementation of ActivationGroup will set the system properties to the system properties in force when its ActivationGroupDesc was created, and will set the security manager to the java.rmi.RMISecurityManager. If your application requires some specific properties to be set when objects are activated in the group, the application should set the properties before creating any ActivationDescs (before the default ActivationGroupDesc is created). If your application requires the use of a security manager other than the RMISecurityManager, set the following two properties to specify the SecurityManager class and codebase:
- java.rmi.activation.security.class
- java.rmi.activation.security.codebase
Since:
JDK1.2
See Also:
ActivationInstantiator, ActivationGroupDesc, ActivationGroupID

ActivationGroup(ActivationGroupID)
Constructs and exports an activation group.

activeObject(ActivationID, MarshalledObject)
This protected method is necessary for subclasses to make the activeObject callback to the group's monitor.
activeObject(ActivationID, Remote)
The group's activeObject method is called when an object is exported (either by Activatable object construction or an explicit call to Activatable.exportObject.
createGroup(ActivationGroupID, ActivationGroupDesc, long)
Create and set the activation group for the current VM.
currentGroupID()
Returns the current activation group's identifier.
getSystem()
Returns the activation system for the VM.
inactiveGroup()
This protected method is necessary for subclasses to make the inactiveGroup callback to the group's monitor.
inactiveObject(ActivationID)
The group's inactiveObject method is called indirectly via a call to the Activatable.inactive method.
newInstance(ActivationID, ActivationDesc)
Creates a new instance of an activatable remote object.
setSystem(ActivationSystem)
Set the activation system for the VM.
ActivationGroup protected ActivationGroup(ActivationGroupID groupID) throws RemoteException Constructs and exports an activation group. Parameters: groupID - the group's identifier Throws: RemoteException if group could not be exported newInstance public abstract MarshalledObject newInstance(ActivationID id, ActivationDesc desc) throws ActivationException Creates a new instance of an activatable remote object. The Activator calls this method to create an activatable object in this group. Parameters: id - the object's activation identifier desc - the object's activation descriptor Returns: a marshalled object containing the activated object's stub inactiveObject public void 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 collector since the group keeps strong references to the objects it creates. The group's inactiveObject method forcibly unexports the remote object from the RMI runtime so that the object can no longer receive incoming RMI calls. After removing the object from the RMI runtime, the group informs 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. Parameters: id - the object's activation identifier Throws: UnknownObjectException if object is unknown (may already be inactive) Throws: RemoteException if call informing monitor fails activeObject public abstract 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. Parameters: id - the object's identifier obj - the remote object implementation Throws: UnknownObjectException if object is not registered Throws: RemoteException if call informing monitor fails createGroup public static 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 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. Note: if your application creates its own custom activation group, the group must set a security manager in the constructor, or objects cannot be activated in the group. 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. Parameters: id - the activation group's identifier desc - the activation group's descriptor incarnation - the group's incarnation number Returns: the activation group for the VM Throws: ActivationException if group already exists or if error occurs during group creation currentGroupID public static ActivationGroupID currentGroupID() Returns the current activation group's identifier. Returns null if no group is currently active for this VM. Returns: the activation group's identifier setSystem public static 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. Parameters: system - remote reference to the ActivationSystem Throws: ActivationException if activation system is already set getSystem public static 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. Returns: the activation system for the VM/group Throws: if activation system cannot be obtained or is not bound (means that it is not running) activeObject protected void activeObject(ActivationID id, MarshalledObject 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. Parameters: id - the object's identifier mobj - a marshalled object containing the remote object's stub Throws: UnknownObjectException if object is not registered Throws: RemoteException if call informing monitor fails inactiveGroup 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. Throws: UnknownGroupException if group is not registered Throws: RemoteException if call informing monitor fails All Packages Class Hierarchy This Package Previous Next Index Submit a bug or feature