- java.lang.Object
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- java.rmi.server.RemoteObject
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- java.rmi.server.RemoteServer
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- java.rmi.server.UnicastRemoteObject
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- java.rmi.activation.ActivationGroup
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- All Implemented Interfaces:
Serializable,ActivationInstantiator,Remote
public abstract class ActivationGroup extends UnicastRemoteObject implements ActivationInstantiator
AnActivationGroupis responsible for creating new instances of "activatable" objects in its group, informing itsActivationMonitorwhen either: its object's become active or inactive, or the group as a whole becomes inactive.An
ActivationGroupis initially created in one of several ways:- as a side-effect of creating an
ActivationDescwithout an explicitActivationGroupIDfor the first activatable object in the group, or - via the
ActivationGroup.createGroupmethod - as a side-effect of activating the first object in a group
whose
ActivationGroupDescwas 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 theActivationGroup.createGroupstatic method. ThecreateGroupmethod has two requirements on the group to be created: 1) the group must be a concrete subclass ofActivationGroup, 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
ActivationGroupwill override the system properties with the properties requested when itsActivationGroupDescwas created, and will set aSecurityManageras 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 specialPropertiesobject containing these properties, then create anActivationGroupDescwith thePropertiesobject, and useActivationGroup.createGroupbefore creating anyActivationDescs (before the defaultActivationGroupDescis created). If your application requires the use of a security manager other thanSecurityManager, in the ActivativationGroupDescriptor properties list you can setjava.security.managerproperty to the name of the security manager you would like to install.- Since:
- 1.2
- See Also:
ActivationInstantiator,ActivationGroupDesc,ActivationGroupID, Serialized Form
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Field Summary
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Fields declared in class java.rmi.server.RemoteObject
ref
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Constructor Summary
Constructors Modifier Constructor Description protectedActivationGroup(ActivationGroupID groupID)Constructs an activation group with the given activation group identifier.
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Method Summary
All Methods Static Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description protected voidactiveObject(ActivationID id, MarshalledObject<? extends Remote> mobj)This protected method is necessary for subclasses to make theactiveObjectcallback to the group's monitor.abstract voidactiveObject(ActivationID id, Remote obj)The group'sactiveObjectmethod is called when an object is exported (either byActivatableobject construction or an explicit call toActivatable.exportObject.static ActivationGroupcreateGroup(ActivationGroupID id, ActivationGroupDesc desc, long incarnation)Create and set the activation group for the current VM.static ActivationGroupIDcurrentGroupID()Returns the current activation group's identifier.static ActivationSystemgetSystem()Returns the activation system for the VM.protected voidinactiveGroup()This protected method is necessary for subclasses to make theinactiveGroupcallback to the group's monitor.booleaninactiveObject(ActivationID id)The group'sinactiveObjectmethod is called indirectly via a call to theActivatable.inactivemethod.static voidsetSystem(ActivationSystem system)Set the activation system for the VM.-
Methods declared in class java.rmi.server.UnicastRemoteObject
clone, exportObject, exportObject, exportObject, exportObject, exportObject, unexportObject
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Methods declared in class java.rmi.server.RemoteServer
getClientHost, getLog, setLog
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Methods declared in interface java.rmi.activation.ActivationInstantiator
newInstance
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Constructor Detail
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ActivationGroup
protected ActivationGroup(ActivationGroupID groupID) throws RemoteException
Constructs an activation group with the given activation group identifier. The group is exported as ajava.rmi.server.UnicastRemoteObject.- Parameters:
groupID- the group's identifier- Throws:
RemoteException- if this group could not be exportedUnsupportedOperationException- if and only if activation is not supported by this implementation- Since:
- 1.2
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Method Detail
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inactiveObject
public boolean inactiveObject(ActivationID id) throws ActivationException, UnknownObjectException, RemoteException
The group'sinactiveObjectmethod is called indirectly via a call to theActivatable.inactivemethod. A remote object implementation must callActivatable'sinactivemethod when that object deactivates (the object deems that it is no longer active). If the object does not callActivatable.inactivewhen it deactivates, the object will never be garbage collected since the group keeps strong references to the objects it creates.The group's
inactiveObjectmethod 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 ofActivationGroupmust override this method and unexport the object.After removing the object from the RMI runtime, the group must inform its
ActivationMonitor(via the monitor'sinactiveObjectmethod) 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.
- Parameters:
id- the object's activation identifier- Returns:
- true if the object was successfully deactivated; otherwise returns false.
- Throws:
UnknownObjectException- if object is unknown (may already be inactive)RemoteException- if call informing monitor failsActivationException- if group is inactive- Since:
- 1.2
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activeObject
public abstract void activeObject(ActivationID id, Remote obj) throws ActivationException, UnknownObjectException, RemoteException
The group'sactiveObjectmethod is called when an object is exported (either byActivatableobject construction or an explicit call toActivatable.exportObject. The group must inform itsActivationMonitorthat the object is active (via the monitor'sactiveObjectmethod) if the group hasn't already done so.- Parameters:
id- the object's identifierobj- the remote object implementation- Throws:
UnknownObjectException- if object is not registeredRemoteException- if call informing monitor failsActivationException- if group is inactive- Since:
- 1.2
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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 thecreateGroupmethod when theActivatorinitiates the re-creation of an activation group in order to carry out incomingactivaterequests. A group must first be registered with theActivationSystembefore it can be created via this method.The group class specified by the
ActivationGroupDescmust be a concrete subclass ofActivationGroupand have a public constructor that takes two arguments: theActivationGroupIDfor the group and theMarshalledObjectcontaining the group's initialization data (obtained from theActivationGroupDesc.If the group class name specified in the
ActivationGroupDescisnull, 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.
SecurityManageris set by default.If a security manager is already set in the group VM, this method first calls the security manager's
checkSetFactorymethod. This could result in aSecurityException. If your application needs to set a different security manager, you must ensure that the policy file specified by the group'sActivationGroupDescgrants 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
ActivationSystemis informed that the group is active by calling theactiveGroupmethod which returns theActivationMonitorfor the group. The application need not callactiveGroupindependently since it is taken care of by this method.Once a group is created, subsequent calls to the
currentGroupIDmethod will return the identifier for this group until the group becomes inactive.- Parameters:
id- the activation group's identifierdesc- the activation group's descriptorincarnation- the group's incarnation number (zero on group's initial creation)- Returns:
- the activation group for the VM
- Throws:
ActivationException- if group already exists or if error occurs during group creationSecurityException- if permission to create group is denied. (Note: The default implementation of the security managercheckSetFactorymethod requires the RuntimePermission "setFactory")UnsupportedOperationException- if and only if activation is not supported by this implementation- Since:
- 1.2
- See Also:
SecurityManager.checkSetFactory()
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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
- Throws:
UnsupportedOperationException- if and only if activation is not supported by this implementation- Since:
- 1.2
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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 thegetSystemmethod attempts to obtain a reference to theActivationSystemby 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 byActivationSystem.SYSTEM_PORT. This port can be overridden by setting the propertyjava.rmi.activation.port.If there is a security manager, this method first calls the security manager's
checkSetFactorymethod. This could result in a SecurityException.- Parameters:
system- remote reference to theActivationSystem- Throws:
ActivationException- if activation system is already setSecurityException- if permission to set the activation system is denied. (Note: The default implementation of the security managercheckSetFactorymethod requires the RuntimePermission "setFactory")UnsupportedOperationException- if and only if activation is not supported by this implementation- Since:
- 1.2
- See Also:
getSystem(),SecurityManager.checkSetFactory()
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getSystem
public static ActivationSystem getSystem() throws ActivationException
Returns the activation system for the VM. The activation system may be set by thesetSystemmethod. If the activation system is not set via thesetSystemmethod, then thegetSystemmethod attempts to obtain a reference to theActivationSystemby 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 byActivationSystem.SYSTEM_PORT. This port can be overridden by setting the propertyjava.rmi.activation.port.- Returns:
- the activation system for the VM/group
- Throws:
ActivationException- if activation system cannot be obtained or is not bound (means that it is not running)UnsupportedOperationException- if and only if activation is not supported by this implementation- Since:
- 1.2
- See Also:
setSystem(java.rmi.activation.ActivationSystem)
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activeObject
protected void activeObject(ActivationID id, MarshalledObject<? extends Remote> mobj) throws ActivationException, UnknownObjectException, RemoteException
This protected method is necessary for subclasses to make theactiveObjectcallback to the group's monitor. The call is simply forwarded to the group'sActivationMonitor.- Parameters:
id- the object's identifiermobj- a marshalled object containing the remote object's stub- Throws:
UnknownObjectException- if object is not registeredRemoteException- if call informing monitor failsActivationException- if an activation error occurs- Since:
- 1.2
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inactiveGroup
protected void inactiveGroup() throws UnknownGroupException, RemoteExceptionThis protected method is necessary for subclasses to make theinactiveGroupcallback to the group's monitor. The call is simply forwarded to the group'sActivationMonitor. Also, the current group for the VM is set to null.- Throws:
UnknownGroupException- if group is not registeredRemoteException- if call informing monitor fails- Since:
- 1.2
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