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PortableRemoteObject.javaAPI DocJava SE 5 API11810Fri Aug 26 14:54:24 BST 2005com.sun.corba.se.impl.javax.rmi

PortableRemoteObject

public class PortableRemoteObject extends Object implements PortableRemoteObjectDelegate
Server implementation objects may either inherit from javax.rmi.PortableRemoteObject or they may implement a remote interface and then use the exportObject method to register themselves as a server object. The toStub method takes a server implementation and returns a stub that can be used to access that server object. The connect method makes a Remote object ready for remote communication. The unexportObject method is used to deregister a server object, allowing it to become available for garbage collection. The narrow method takes an object reference or abstract interface type and attempts to narrow it to conform to the given interface. If the operation is successful the result will be an object of the specified type, otherwise an exception will be thrown.

Fields Summary
Constructors Summary
Methods Summary
public voidconnect(java.rmi.Remote target, java.rmi.Remote source)
Makes a Remote object ready for remote communication. This normally happens implicitly when the object is sent or received as an argument on a remote method call, but in some circumstances it is useful to perform this action by making an explicit call. See the {@link Stub#connect} method for more information.

param
target the object to connect.
param
source a previously connected object.
throws
RemoteException if source is not connected or if target is already connected to a different ORB than source.

        if (target == null || source == null) {
            throw new NullPointerException("invalid argument");
        }
 
        ORB orb = null;
        try {
	    if (StubAdapter.isStub( source )) {
		orb = StubAdapter.getORB( source ) ;
            } else {
                // Is this a servant that was exported to iiop?
                Tie tie = Util.getTie(source);
                if (tie == null) {
		    /* loadTie always succeeds for dynamic RMI-IIOP
                    // No, can we get a tie for it?  If not,
                    // assume that source is a JRMP object...
                    if (Utility.loadTie(source) != null) {
                        // Yes, so it is an iiop object which
                        // has not been exported...
                        throw new RemoteException(
			    "'source' object not exported"); 
                    }
		    */
                } else {
                    orb = tie.orb();
                }
            }
        } catch (SystemException e) {
            throw new RemoteException("'source' object not connected", e ); 
        }

        boolean targetIsIIOP = false ;
        Tie targetTie = null;
        if (StubAdapter.isStub(target)) {
            targetIsIIOP = true;
        } else {
            targetTie = Util.getTie(target);
            if (targetTie != null) {
                targetIsIIOP = true;
            } else {
		/* loadTie always succeeds for dynamic RMI-IIOP
                if (Utility.loadTie(target) != null) {
                    throw new RemoteException("'target' servant not exported");
                }    
		*/
            }
        }

        if (!targetIsIIOP) {
            // Yes. Do we have an ORB from the source object? 
            // If not, we're done - there is nothing to do to
            // connect a JRMP object. If so, it is an error because
            // the caller mixed JRMP and IIOP...
            if (orb != null) {
                throw new RemoteException(
		    "'source' object exported to IIOP, 'target' is JRMP");
            }
        } else {
            // The target object is IIOP. Make sure we have a
            // valid ORB from the source object...
            if (orb == null) {
                throw new RemoteException(
		    "'source' object is JRMP, 'target' is IIOP");                
            }
            
            // And, finally, connect it up...
            try {
                if (targetTie != null) {
                    // Is the tie already connected?
                    try {
                        ORB existingOrb = targetTie.orb();
                        
                        // Yes. Is it the same orb? 
                        if (existingOrb == orb) {
                            
                            // Yes, so nothing to do...
                            return;
                        } else {
                            // No, so this is an error...
                            throw new RemoteException(
				"'target' object was already connected");
                        }
                    } catch (SystemException e) {}
                    
                    // No, so do it...
                    targetTie.orb(orb);
                } else {
		    StubAdapter.connect( target, orb ) ;
                }
            } catch (SystemException e) {
                
                // The stub or tie was already connected...
                throw new RemoteException(
		    "'target' object was already connected", e ); 
            }
        }
    
public voidexportObject(java.rmi.Remote obj)
Makes a server object ready to receive remote calls. Note that subclasses of PortableRemoteObject do not need to call this method, as it is called by the constructor.

param
obj the server object to export.
exception
RemoteException if export fails.


        if (obj == null) {
            throw new NullPointerException("invalid argument");
        }
    
        // Has this object already been exported to IIOP?
        
        if (Util.getTie(obj) != null) {
        
            // Yes, so this is an error...
            
            throw new ExportException (obj.getClass().getName() + " already exported");
        }
        
        // Can we load a Tie?
        
        Tie theTie = Utility.loadTie(obj);
        
        if (theTie != null) {
        
            // Yes, so export it to IIOP...
            
            Util.registerTarget(theTie,obj);
            
        } else {
            
            // No, so export to JRMP. If this is called twice for the
            // same object, it will throw an ExportException...
            
	    UnicastRemoteObject.exportObject(obj);
        }
    
public java.lang.Objectnarrow(java.lang.Object narrowFrom, java.lang.Class narrowTo)
Checks to ensure that an object of a remote or abstract interface type can be cast to a desired type.

param
narrowFrom the object to check.
param
narrowTo the desired type.
return
an object which can be cast to the desired type.
throws
ClassCastException if narrowFrom cannot be cast to narrowTo.

        java.lang.Object result = null;

        if (narrowFrom == null)
            return null;

        if (narrowTo == null) 
            throw new NullPointerException("invalid argument");

        try { 
            if (narrowTo.isAssignableFrom(narrowFrom.getClass())) 
                return narrowFrom;

	    // Is narrowTo an interface that might be
	    // implemented by a servant running on iiop?
	    if (narrowTo.isInterface() && 
		narrowTo != java.io.Serializable.class &&
		narrowTo != java.io.Externalizable.class) {
	
		org.omg.CORBA.Object narrowObj 
		    = (org.omg.CORBA.Object) narrowFrom;                
		
		// Create an id from the narrowTo type...
		String id = RepositoryId.createForAnyType(narrowTo);
		
		if (narrowObj._is_a(id)) {
		    return Utility.loadStub(narrowObj,narrowTo);
		} else {
		    throw new ClassCastException( "Object is not of remote type " +
			narrowTo.getName() ) ;
		}
	    } else {
		throw new ClassCastException( "Class " + narrowTo.getName() + 
		    " is not a valid remote interface" ) ;
	    }
        } catch(Exception error) {
	    ClassCastException cce = new ClassCastException() ;
	    cce.initCause( error ) ;
	    throw cce ;
        }
    
public java.rmi.RemotetoStub(java.rmi.Remote obj)
Returns a stub for the given server object.

param
obj the server object for which a stub is required. Must either be a subclass of PortableRemoteObject or have been previously the target of a call to {@link #exportObject}.
return
the most derived stub for the object.
exception
NoSuchObjectException if a stub cannot be located for the given server object.

        Remote result = null;
        if (obj == null) {
            throw new NullPointerException("invalid argument");
        }
        
        // If the class is already an IIOP stub then return it.
        if (StubAdapter.isStub( obj )) {
            return obj;
        }
        
        // If the class is already a JRMP stub then return it.
        if (obj instanceof java.rmi.server.RemoteStub) {
            return obj;
        }
            
        // Has it been exported to IIOP?
        Tie theTie = Util.getTie(obj);
        
        if (theTie != null) {
            result = Utility.loadStub(theTie,null,null,true);
        } else {
            if (Utility.loadTie(obj) == null) {
                result = java.rmi.server.RemoteObject.toStub(obj);
            }
        }
        
        if (result == null) {
            throw new NoSuchObjectException("object not exported");
        }
        
        return result;
    
public voidunexportObject(java.rmi.Remote obj)
Deregisters a server object from the runtime, allowing the object to become available for garbage collection.

param
obj the object to unexport.
exception
NoSuchObjectException if the remote object is not currently exported.

	    
        if (obj == null) {
            throw new NullPointerException("invalid argument");
        }
        
        if (StubAdapter.isStub(obj) ||
            obj instanceof java.rmi.server.RemoteStub) {
            throw new NoSuchObjectException( 
		"Can only unexport a server object.");
        }
        
        Tie theTie = Util.getTie(obj);
        if (theTie != null) {
	    Util.unexportObject(obj);
	} else {
	    if (Utility.loadTie(obj) == null) {
    	        UnicastRemoteObject.unexportObject(obj,true);
            } else {
                throw new NoSuchObjectException("Object not exported.");
            }
	}