java.rmi.activation
class Activatable

java.lang.Object java.rmi.server.RemoteObject java.rmi.server.RemoteServer java.rmi.activation.Activatable

All Implemented Interfaces:

Serializable, Remote

public abstract class Activatable
extends RemoteServer

The Activatable class provides support for remote objects that require persistent access over time and that can be activated by the system.

For the constructors and static exportObject methods, the stub for a remote object being exported is obtained as described in {@link java.rmi.server.UnicastRemoteObject}.

An attempt to serialize explicitly an instance of this class will fail.

Activatable

protected Activatable(ActivationID id,
                      int port)
               throws RemoteException

Constructor used to activate/export the object on a specified port. An "activatable" remote object must have a constructor that takes two arguments:

• the object's activation identifier (ActivationID), and
• the object's initialization data (a MarshalledObject).

A concrete subclass of this class must call this constructor when it is activated via the two parameter constructor described above. As a side-effect of construction, the remote object is "exported" to the RMI runtime (on the specified port) and is available to accept incoming calls from clients.

Parameters:

id - activation identifier for the object

port - the port number on which the object is exported

Throws:

RemoteException - if exporting the object to the RMI runtime fails

Activatable

protected Activatable(ActivationID id,
                      int port,
                      RMIClientSocketFactory csf,
                      RMIServerSocketFactory ssf)
               throws RemoteException

Constructor used to activate/export the object on a specified port. An "activatable" remote object must have a constructor that takes two arguments:

• the object's activation identifier (ActivationID), and
• the object's initialization data (a MarshalledObject).

A concrete subclass of this class must call this constructor when it is activated via the two parameter constructor described above. As a side-effect of construction, the remote object is "exported" to the RMI runtime (on the specified port) and is available to accept incoming calls from clients.

Parameters:

id - activation identifier for the object

port - the port number on which the object is exported

csf - the client-side socket factory for making calls to the remote object

ssf - the server-side socket factory for receiving remote calls

Throws:

RemoteException - if exporting the object to the RMI runtime fails

Activatable

protected Activatable(String location,
                      MarshalledObject data,
                      boolean restart,
                      int port)
               throws ActivationException,
                      RemoteException

Constructs an activatable remote object by registering an activation descriptor (with the specified location, data, and restart mode) for this object, and exporting the object with the specified port.

Note: Using the Activatable constructors that both register and export an activatable remote object is strongly discouraged because the actions of registering and exporting the remote object are not guaranteed to be atomic. Instead, an application should register an activation descriptor and export a remote object separately, so that exceptions can be handled properly.

This method invokes the {@link exportObject(Remote,String,MarshalledObject,boolean,port) exportObject} method with this object, and the specified location, data, restart mode, and port. Subsequent calls to {@link #getID} will return the activation identifier returned from the call to exportObject.

Parameters:

location - the location for classes for this object

data - the object's initialization data

restart - if true, the object is restarted (reactivated) when either the activator is restarted or the object's activation group is restarted after an unexpected crash; if false, the object is only activated on demand. Specifying restart to be true does not force an initial immediate activation of a newly registered object; initial activation is lazy.

port - the port on which the object is exported (an anonymous port is used if port=0)

Throws:

ActivationException - if object registration fails.

RemoteException - if either of the following fails: a) registering the object with the activation system or b) exporting the object to the RMI runtime.

Activatable

protected Activatable(String location,
                      MarshalledObject data,
                      boolean restart,
                      int port,
                      RMIClientSocketFactory csf,
                      RMIServerSocketFactory ssf)
               throws ActivationException,
                      RemoteException

Constructs an activatable remote object by registering an activation descriptor (with the specified location, data, and restart mode) for this object, and exporting the object with the specified port, and specified client and server socket factories.

Note: Using the Activatable constructors that both register and export an activatable remote object is strongly discouraged because the actions of registering and exporting the remote object are not guaranteed to be atomic. Instead, an application should register an activation descriptor and export a remote object separately, so that exceptions can be handled properly.

This method invokes the {@link exportObject(Remote,String,MarshalledObject,boolean,port,RMIClientSocketFactory,RMIServerSocketFactory) exportObject} method with this object, and the specified location, data, restart mode, port, and client and server socket factories. Subsequent calls to {@link #getID} will return the activation identifier returned from the call to exportObject.

Parameters:

location - the location for classes for this object

data - the object's initialization data

restart - if true, the object is restarted (reactivated) when either the activator is restarted or the object's activation group is restarted after an unexpected crash; if false, the object is only activated on demand. Specifying restart to be true does not force an initial immediate activation of a newly registered object; initial activation is lazy.

port - the port on which the object is exported (an anonymous port is used if port=0)

csf - the client-side socket factory for making calls to the remote object

ssf - the server-side socket factory for receiving remote calls

Throws:

ActivationException - if object registration fails.

RemoteException - if either of the following fails: a) registering the object with the activation system or b) exporting the object to the RMI runtime.

exportObject

public static Remote exportObject(Remote obj,
                                  ActivationID id,
                                  int port)
                           throws RemoteException

Export the activatable remote object to the RMI runtime to make the object available to receive incoming calls. The object is exported on an anonymous port, if port is zero.

During activation, this exportObject method should be invoked explicitly by an "activatable" object, that does not extend the Activatable class. There is no need for objects that do extend the Activatable class to invoke this method directly because the object is exported during construction.

Parameters:

obj - the remote object implementation

id - the object's activation identifier

port - the port on which the object is exported (an anonymous port is used if port=0)

Returns:

the stub for the activatable remote object

Throws:

RemoteException - if object export fails

exportObject

public static Remote exportObject(Remote obj,
                                  ActivationID id,
                                  int port,
                                  RMIClientSocketFactory csf,
                                  RMIServerSocketFactory ssf)
                           throws RemoteException

Export the activatable remote object to the RMI runtime to make the object available to receive incoming calls. The object is exported on an anonymous port, if port is zero.

During activation, this exportObject method should be invoked explicitly by an "activatable" object, that does not extend the Activatable class. There is no need for objects that do extend the Activatable class to invoke this method directly because the object is exported during construction.

Parameters:

obj - the remote object implementation

id - the object's activation identifier

port - the port on which the object is exported (an anonymous port is used if port=0)

csf - the client-side socket factory for making calls to the remote object

ssf - the server-side socket factory for receiving remote calls

Returns:

the stub for the activatable remote object

Throws:

RemoteException - if object export fails

exportObject

public static ActivationID exportObject(Remote obj,
                                        String location,
                                        MarshalledObject data,
                                        boolean restart,
                                        int port)
                                 throws ActivationException,
                                        RemoteException

Registers an activation descriptor (with the specified location, data, and restart mode) for the specified object, and exports that object with the specified port.

Note: Using this method (as well as the Activatable constructors that both register and export an activatable remote object) is strongly discouraged because the actions of registering and exporting the remote object are not guaranteed to be atomic. Instead, an application should register an activation descriptor and export a remote object separately, so that exceptions can be handled properly.

This method invokes the {@link exportObject(Remote,String,MarshalledObject,boolean,port,RMIClientSocketFactory,RMIServerSocketFactory) exportObject} method with the specified object, location, data, restart mode, and port, and null for both client and server socket factories, and then returns the resulting activation identifier.

Parameters:

obj - the object being exported

location - the object's code location

data - the object's bootstrapping data

restart - if true, the object is restarted (reactivated) when either the activator is restarted or the object's activation group is restarted after an unexpected crash; if false, the object is only activated on demand. Specifying restart to be true does not force an initial immediate activation of a newly registered object; initial activation is lazy.

port - the port on which the object is exported (an anonymous port is used if port=0)

Returns:

the activation identifier obtained from registering the descriptor, desc, with the activation system the wrong group

Throws:

ActivationException - if activation group is not active

RemoteException - if object registration or export fails

exportObject

public static ActivationID exportObject(Remote obj,
                                        String location,
                                        MarshalledObject data,
                                        boolean restart,
                                        int port,
                                        RMIClientSocketFactory csf,
                                        RMIServerSocketFactory ssf)
                                 throws ActivationException,
                                        RemoteException

Registers an activation descriptor (with the specified location, data, and restart mode) for the specified object, and exports that object with the specified port, and the specified client and server socket factories.

Note: Using this method (as well as the Activatable constructors that both register and export an activatable remote object) is strongly discouraged because the actions of registering and exporting the remote object are not guaranteed to be atomic. Instead, an application should register an activation descriptor and export a remote object separately, so that exceptions can be handled properly.

This method first registers an activation descriptor for the specified object as follows. It obtains the activation system by invoking the method {@link ActivationGroup#getSystem ActivationGroup.getSystem}. This method then obtains an {@link ActivationID} for the object by invoking the activation system's {@link ActivationSystem#registerObject registerObject} method with an {@link ActivationDesc} constructed with the specified object's class name, and the specified location, data, and restart mode. If an exception occurs obtaining the activation system or registering the activation descriptor, that exception is thrown to the caller.

Next, this method exports the object by invoking the {@link #exportObject(Remote,ActivationID,int,RMIClientSocketFactory,RMIServerSocketFactory) exportObject} method with the specified remote object, the activation identifier obtained from registration, the specified port, and the specified client and server socket factories. If an exception occurs exporting the object, this method attempts to unregister the activation identifier (obtained from registration) by invoking the activation system's {@link ActivationSystem#unregisterObject unregisterObject} method with the activation identifier. If an exception occurs unregistering the identifier, that exception is ignored, and the original exception that occurred exporting the object is thrown to the caller.

Finally, this method invokes the {@link ActivationGroup#activeObject activeObject} method on the activation group in this VM with the activation identifier and the specified remote object, and returns the activation identifier to the caller.

Parameters:

obj - the object being exported

location - the object's code location

data - the object's bootstrapping data

restart - if true, the object is restarted (reactivated) when either the activator is restarted or the object's activation group is restarted after an unexpected crash; if false, the object is only activated on demand. Specifying restart to be true does not force an initial immediate activation of a newly registered object; initial activation is lazy.

port - the port on which the object is exported (an anonymous port is used if port=0)

csf - the client-side socket factory for making calls to the remote object

ssf - the server-side socket factory for receiving remote calls

Returns:

the activation identifier obtained from registering the descriptor with the activation system

Throws:

ActivationException - if activation group is not active

RemoteException - if object registration or export fails

getID

protected ActivationID getID()

Returns the object's activation identifier. The method is protected so that only subclasses can obtain an object's identifier.

Returns:

the object's activation identifier

inactive

public static boolean inactive(ActivationID id)
                        throws UnknownObjectException,
                               ActivationException,
                               RemoteException

Informs the system that the object with the corresponding activation id is currently inactive. If the object is currently active, the object is "unexported" from the RMI runtime (only if there are no pending or in-progress calls) so the that it can no longer receive incoming calls. This call informs this VM's ActivationGroup that the object is inactive, that, in turn, informs its ActivationMonitor. If this call completes successfully, a subsequent activate request to the activator will cause the object to reactivate. The operation may still succeed if the object is considered active but has already unexported itself.

Parameters:

id - the object's activation identifier

Returns:

true if the operation succeeds (the operation will succeed if the object in currently known to be active and is either already unexported or is currently exported and has no pending/executing calls); false is returned if the object has pending/executing calls in which case it cannot be deactivated

Throws:

UnknownObjectException - if object is not known (it may already be inactive)

ActivationException - if group is not active

RemoteException - if call informing monitor fails

register

public static Remote register(ActivationDesc desc)
                       throws UnknownGroupException,
                              ActivationException,
                              RemoteException

Register an object descriptor for an activatable remote object so that is can be activated on demand.

Parameters:

desc - the object's descriptor

Returns:

the stub for the activatable remote object

Throws:

UnknownGroupException - if group id in desc is not registered with the activation system

ActivationException - if activation system is not running

RemoteException - if remote call fails

unexportObject

public static boolean unexportObject(Remote obj,
                                     boolean force)
                              throws NoSuchObjectException

Remove the remote object, obj, from the RMI runtime. If successful, the object can no longer accept incoming RMI calls. If the force parameter is true, the object is forcibly unexported even if there are pending calls to the remote object or the remote object still has calls in progress. If the force parameter is false, the object is only unexported if there are no pending or in progress calls to the object.

Parameters:

obj - the remote object to be unexported

force - if true, unexports the object even if there are pending or in-progress calls; if false, only unexports the object if there are no pending or in-progress calls

Returns:

true if operation is successful, false otherwise

Throws:

NoSuchObjectException - if the remote object is not currently exported

unregister

public static void unregister(ActivationID id)
                       throws UnknownObjectException,
                              ActivationException,
                              RemoteException

Revokes previous registration for the activation descriptor associated with id. An object can no longer be activated via that id.

Parameters:

id - the object's activation identifier

Throws:

UnknownObjectException - if object (id) is unknown

ActivationException - if activation system is not running

RemoteException - if remote call to activation system fails