This section contains the interfaces and classes used by the stubs and skeletons generated by the rmic stub compiler.

Topics:

• The RemoteStub Class
• The RemoteCall Interface
• The RemoteRef Interface
• The ServerRef Interface
• The Skeleton Interface
• The Operation Class

The RemoteStub Class

package java.rmi.server;

public abstract class RemoteStub extends java.rmi.RemoteObject {}

The RemoteCall Interface

package java.rmi.server;
import java.io.*;

public interface RemoteCall {

	ObjectOutput getOutputStream() throws IOException;

	void releaseOutputStream() throws IOException;

	ObjectInput getInputStream() throws IOException;

	void releaseInputStream() throws IOException;

	ObjectOutput getResultStream(boolean success)
		throws IOException, StreamCorruptedException;

	void executeCall() throws Exception;

	void done() throws IOException;
}

The method releaseOutputStream releases the output stream; in some transports this will release the stream.

The method getInputStream returns the InputStream from which the stub unmarshals results or the skeleton unmarshals parameters.

The method releaseInputStream releases the input stream. This will allow some transports to release the input side of a connection early.

The method getResultStream returns an output stream (after writing out header information relating to the success of the call). Obtaining a result stream should only succeed once per remote call. If success is true, then the result to be marshaled is a normal return; otherwise the result is an exception. StreamCorruptedException is thrown if the result stream has already been obtained for this remote call.

The method executeCall does whatever it takes to execute the call.

The method done allows cleanup after the remote call has completed.

The RemoteRef Interface

package java.rmi.server;

public interface RemoteRef extends java.io.Externalizable {

	RemoteCall newCall(RemoteObject obj, Operation[] op, int opnum,
		long hash) throws RemoteException;

	void invoke(RemoteCall call) throws Exception;

	void done(RemoteCall call) throws RemoteException;

	String getRefClass(java.io.ObjectOutput out);

	int remoteHashCode();

	boolean remoteEquals(RemoteRef obj);

	String remoteToString();
}

The method invoke executes the remote call. invoke will raise any "user" exceptions which should pass through and not be caught by the stub. If any exception is raised during the remote invocation, invoke should take care of cleaning up the connection before raising the "user exception" or RemoteException.

The method done allows the remote reference to clean up (or reuse) the connection. done should only be called if the invoke call returns successfully (non-exceptionally) to the stub.

The method getRefClass returns the nonpackage-qualified class name of the reference type to be serialized onto the stream out.

The method remoteHashCode returns a hashcode for a remote object. Two remote object stubs that refer to the same remote object will have the same hash code (in order to support remote objects as keys in hashtables). A RemoteObject forwards a call to its hashCode method to the remoteHashCode method of the remote reference.

The method remoteEquals compares two remote objects for equality. Two remote objects are equal if they refer to the same remote object. For example, two stubs are equal if they refer to the same remote object. A RemoteObject forwards a call to its equals method to the remoteEquals method of the remote reference.

The method remoteToString returns a String that represents the reference of this remote object.

The ServerRef Interface

package java.rmi.server;

public interface ServerRef extends RemoteRef {

	RemoteStub exportObject(java.rmi.Remote obj, Object data)
		throws java.rmi.RemoteException;

	String getClientHost() throws ServerNotActiveException;
}

The method getClientHost returns the host name of the current client. When called from a thread actively handling a remote method invocation, the host name of the client invoking the call is returned. If a remote method call is not currently being service, then ServerNotActiveException is called.

The Skeleton Interface

package java.rmi.server;

public interface Skeleton {

    void dispatch(Remote obj, RemoteCall call, int opnum, long hash)
		throws Exception;

    Operation[] getOperations();
}

The getOperations method returns an array containing the operation descriptors for the remote object's methods.

The Operation Class

package java.rmi.server;

public class Operation {

	public Operation(String op);

	public String getOperation();

	public String toString();
}

The method getOperation returns the contents of the operation descriptor (the value with which it was initialized).

The method toString also returns the string representation of the operation descriptor (typically the method signature).