IBM User Guide for Java V7 on Windows > Developing Java applications > RMI over IIOP > RMI-IIOP Programmer's Guide > Using RMI-IIOP

Connecting IIOP stubs to the ORB

When your application uses IIOP stubs, as opposed to JRMP stubs, you must properly connect the IIOP stubs with the ORB before starting operations on the IIOP stubs (this is not necessary with JRMP stubs). This section discusses the extra 'connect' step required for the IIOP stub case.

The PortableRemoteObject.exportObject() call only creates a Tie object and caches it for future usage. The created tie does not have a delegate or an ORB associated. This is known as explicit invocation.

The PortableRemoteObject.exportObject() happens automatically when the servant instance is created. The servant instance is created when a PortableRemoteObject constructor is called as a base class. This is known as implicit invocation.

Later, when the application calls PortableRemoteObject.toStub(), the ORB creates the corresponding Stub object and associates it with the cached Tie object. But because the Tie is not connected and does not have a delegate, the newly created Stub also does not have a delegate or ORB.

The delegate is set for the stub only when the application calls Stub.connect(orb). Thus, any operations on the stub made before the ORB connection is made will fail.

The Java™ Language to OMG IDL Mapping Specification (http://www.omg.org/cgi-bin/doc?formal/01-06-07) says this about the Stub.connect() method:

"The connect method makes the stub ready for remote communication using the specified ORB object orb. Connection normally happens implicitly when the stub is received or sent as an argument on a remote method call, but it is sometimes useful to do this by making an explicit call (e.g., following deserialization). If the stub is already connected to orb (has a delegate set for orb), then connect takes no action. If the stub is connected to some other ORB, then a RemoteException is thrown. Otherwise, a delegate is created for this stub and the ORB object orb."

For servants that are not POA-activated, Stub.connect(orb) is necessary as a required setup.

Parent: Using RMI-IIOP

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