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115 lines
4.5 KiB
115 lines
4.5 KiB
/*
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* Copyright (c) 1997, 2005, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*/
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package java.rmi.activation;
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import java.rmi.MarshalledObject;
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import java.rmi.Remote;
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import java.rmi.RemoteException;
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import java.rmi.activation.UnknownObjectException;
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/**
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* The <code>Activator</code> facilitates remote object activation. A
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* "faulting" remote reference calls the activator's
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* <code>activate</code> method to obtain a "live" reference to a
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* "activatable" remote object. Upon receiving a request for activation,
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* the activator looks up the activation descriptor for the activation
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* identifier, <code>id</code>, determines the group in which the
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* object should be activated initiates object re-creation via the
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* group's <code>ActivationInstantiator</code> (via a call to the
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* <code>newInstance</code> method). The activator initiates the
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* execution of activation groups as necessary. For example, if an
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* activation group for a specific group identifier is not already
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* executing, the activator initiates the execution of a VM for the
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* group. <p>
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*
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* The <code>Activator</code> works closely with
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* <code>ActivationSystem</code>, which provides a means for registering
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* groups and objects within those groups, and <code>ActivationMonitor</code>,
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* which recives information about active and inactive objects and inactive
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* groups. <p>
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*
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* The activator is responsible for monitoring and detecting when
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* activation groups fail so that it can remove stale remote references
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* to groups and active object's within those groups.<p>
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*
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* @author Ann Wollrath
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* @see ActivationInstantiator
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* @see ActivationGroupDesc
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* @see ActivationGroupID
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* @since 1.2
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*/
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public interface Activator extends Remote {
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/**
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* Activate the object associated with the activation identifier,
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* <code>id</code>. If the activator knows the object to be active
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* already, and <code>force</code> is false , the stub with a
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* "live" reference is returned immediately to the caller;
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* otherwise, if the activator does not know that corresponding
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* the remote object is active, the activator uses the activation
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* descriptor information (previously registered) to determine the
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* group (VM) in which the object should be activated. If an
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* <code>ActivationInstantiator</code> corresponding to the
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* object's group descriptor already exists, the activator invokes
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* the activation group's <code>newInstance</code> method passing
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* it the object's id and descriptor. <p>
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*
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* If the activation group for the object's group descriptor does
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* not yet exist, the activator starts an
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* <code>ActivationInstantiator</code> executing (by spawning a
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* child process, for example). When the activator receives the
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* activation group's call back (via the
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* <code>ActivationSystem</code>'s <code>activeGroup</code>
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* method) specifying the activation group's reference, the
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* activator can then invoke that activation instantiator's
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* <code>newInstance</code> method to forward each pending
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* activation request to the activation group and return the
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* result (a marshalled remote object reference, a stub) to the
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* caller.<p>
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*
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* Note that the activator receives a "marshalled" object instead of a
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* Remote object so that the activator does not need to load the
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* code for that object, or participate in distributed garbage
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* collection for that object. If the activator kept a strong
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* reference to the remote object, the activator would then
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* prevent the object from being garbage collected under the
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* normal distributed garbage collection mechanism. <p>
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*
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* @param id the activation identifier for the object being activated
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* @param force if true, the activator contacts the group to obtain
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* the remote object's reference; if false, returning the cached value
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* is allowed.
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* @return the remote object (a stub) in a marshalled form
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* @exception ActivationException if object activation fails
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* @exception UnknownObjectException if object is unknown (not registered)
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* @exception RemoteException if remote call fails
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* @since 1.2
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*/
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public MarshalledObject<? extends Remote> activate(ActivationID id,
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boolean force)
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throws ActivationException, UnknownObjectException, RemoteException;
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}
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