java.rmi.server

Class UnicastRemoteObject

  • All Implemented Interfaces:
    Serializable, Remote
    Direct Known Subclasses:
    ActivationGroup 

    public class UnicastRemoteObject
extends RemoteServer
    Used for exporting a remote object with JRMP and obtaining a stub that communicates to the remote object. Stubs are either generated at runtime using dynamic proxy objects, or they are generated statically at build time, typically using the rmic tool.

    Deprecated: Static Stubs. Support for statically generated stubs is deprecated. This includes the API in this class that requires the use of static stubs, as well as the runtime support for loading static stubs. Generating stubs dynamically is preferred, using one of the five non-deprecated ways of exporting objects as listed below. Do not run rmic to generate static stub classes. It is unnecessary, and it is also deprecated.

    There are six ways to export remote objects:

    1. Subclassing UnicastRemoteObject and calling the UnicastRemoteObject() constructor.
    2. Subclassing UnicastRemoteObject and calling the UnicastRemoteObject(port) constructor.
    3. Subclassing UnicastRemoteObject and calling the UnicastRemoteObject(port, csf, ssf) constructor.
    4. Calling the exportObject(Remote) method. Deprecated.
    5. Calling the exportObject(Remote, port) method.
    6. Calling the exportObject(Remote, port, csf, ssf) method.

    The fourth technique, exportObject(Remote), always uses statically generated stubs and is deprecated.

    The other five techniques all use the following approach: if the java.rmi.server.ignoreStubClasses property is true (case insensitive) or if a static stub cannot be found, stubs are generated dynamically using Proxy objects. Otherwise, static stubs are used.

    The default value of the java.rmi.server.ignoreStubClasses property is false.

    Statically generated stubs are typically pregenerated from the remote object's class using the rmic tool. A static stub is loaded and an instance of that stub class is constructed as described below.

    • A "root class" is determined as follows: if the remote object's class directly implements an interface that extends Remote, then the remote object's class is the root class; otherwise, the root class is the most derived superclass of the remote object's class that directly implements an interface that extends Remote.
    • The name of the stub class to load is determined by concatenating the binary name of the root class with the suffix _Stub.
    • The stub class is loaded by name using the class loader of the root class. The stub class must extend RemoteStub and must have a public constructor that has one parameter of type RemoteRef.
    • Finally, an instance of the stub class is constructed with a RemoteRef.
    • If the appropriate stub class could not be found, or if the stub class could not be loaded, or if a problem occurs creating the stub instance, a StubNotFoundException is thrown.

    Stubs are dynamically generated by constructing an instance of a Proxy with the following characteristics:

    • The proxy's class is defined by the class loader of the remote object's class.
    • The proxy implements all the remote interfaces implemented by the remote object's class.
    • The proxy's invocation handler is a RemoteObjectInvocationHandler instance constructed with a RemoteRef.
    • If the proxy could not be created, a StubNotFoundException will be thrown.
    Since:
    JDK1.1
    See Also:
    Serialized Form

    • Constructor Detail

      • UnicastRemoteObject

        protected UnicastRemoteObject()
                       throws RemoteException
        Creates and exports a new UnicastRemoteObject object using an anonymous port.

        The object is exported with a server socket created using the RMISocketFactory class.

        Throws:
        RemoteException - if failed to export object
        Since:
        JDK1.1

      • UnicastRemoteObject

        protected UnicastRemoteObject(int port)
                       throws RemoteException
        Creates and exports a new UnicastRemoteObject object using the particular supplied port.

        The object is exported with a server socket created using the RMISocketFactory class.

        Parameters:
        port - the port number on which the remote object receives calls (if port is zero, an anonymous port is chosen)
        Throws:
        RemoteException - if failed to export object
        Since:
        1.2

      • UnicastRemoteObject

        protected UnicastRemoteObject(int port,
                              RMIClientSocketFactory csf,
                              RMIServerSocketFactory ssf)
                       throws RemoteException
        Creates and exports a new UnicastRemoteObject object using the particular supplied port and socket factories.

        Either socket factory may be null, in which case the corresponding client or server socket creation method of RMISocketFactory is used instead.

        Parameters:
        port - the port number on which the remote object receives calls (if port is zero, an anonymous port is chosen)
        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 failed to export object
        Since:
        1.2

    • Method Detail

      • exportObject

        public static Remote exportObject(Remote obj,
                                  int port)
                           throws RemoteException
        Exports the remote object to make it available to receive incoming calls, using the particular supplied port.

        The object is exported with a server socket created using the RMISocketFactory class.

        Parameters:
        obj - the remote object to be exported
        port - the port to export the object on
        Returns:
        remote object stub
        Throws:
        RemoteException - if export fails
        Since:
        1.2

      • exportObject

        public static Remote exportObject(Remote obj,
                                  int port,
                                  RMIClientSocketFactory csf,
                                  RMIServerSocketFactory ssf)
                           throws RemoteException
        Exports the remote object to make it available to receive incoming calls, using a transport specified by the given socket factory.

        Either socket factory may be null, in which case the corresponding client or server socket creation method of RMISocketFactory is used instead.

        Parameters:
        obj - the remote object to be exported
        port - the port to export the object on
        csf - the client-side socket factory for making calls to the remote object
        ssf - the server-side socket factory for receiving remote calls
        Returns:
        remote object stub
        Throws:
        RemoteException - if export fails
        Since:
        1.2

      • unexportObject

        public static boolean unexportObject(Remote obj,
                                     boolean force)
                              throws NoSuchObjectException
        Removes 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
        Since:
        1.2