/*
 * @(#)RMISocketFactory.java	1.16 00/02/02
 *
 * Copyright 1996-2000 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the proprietary information of Sun Microsystems, Inc.  
 * Use is subject to license terms.
 * 
 */

package java.rmi.server;

import java.io.*;
import java.net.*;

/**
 * An <code>RMISocketFactory</code> instance is used by the RMI runtime
 * in order to obtain client and server sockets for RMI calls.  An
 * application may use the <code>setSocketFactory</code> method to
 * request that the RMI runtime use its socket factory instance
 * instead of the default implementation.<p>
 *
 * The default socket factory implementation used goes through a
 * three-tiered approach to creating client sockets. First, a direct
 * socket connection to the remote VM is attempted.  If that fails
 * (due to a firewall), the runtime uses HTTP with the explicit port
 * number of the server.  If the firewall does not allow this type of
 * communication, then HTTP to a cgi-bin script on the server is used
 * to POST the RMI call.<p>
 *
 * @version 1.16, 02/02/00
 * @author  Ann Wollrath
 * @author  Peter Jones
 * @since   JDK1.1
 */
public abstract class RMISocketFactory
	implements RMIClientSocketFactory, RMIServerSocketFactory
{

    /** Client/server socket factory to be used by RMI runtime */
    private static RMISocketFactory factory = null;
    /** default socket factory used by this RMI implementation */
    private static RMISocketFactory defaultSocketFactory;
    /** Handler for socket creation failure */
    private static RMIFailureHandler handler = null;

    /**
     * Constructs an <code>RMISocketFactory</code>.
     * @since JDK1.1
     */
    public RMISocketFactory() {
	super();
    }
    
    /**
     * Creates a client socket connected to the specified host and port.
     * @param  host   the host name
     * @param  port   the port number
     * @return a socket connected to the specified host and port.
     * @exception IOException if an I/O error occurs during socket creation
     * @since JDK1.1
     */
    public abstract Socket createSocket(String host, int port)
	throws IOException;

    /**
     * Create a server socket on the specified port (port 0 indicates
     * an anonymous port).
     * @param  port the port number
     * @return the server socket on the specified port
     * @exception IOException if an I/O error occurs during server socket
     * creation
     * @since JDK1.1
     */
    public abstract ServerSocket createServerSocket(int port)
	throws IOException;

    /**
     * Set the global socket factory from which RMI gets sockets (if the
     * remote object is not associated with a specific client and/or server
     * socket factory). The RMI socket factory can only be set once. Note: The
     * RMISocketFactory may only be set if the current security manager allows
     * setting a socket factory; if disallowed, a SecurityException will be
     * thrown.
     * @param fac the socket factory
     * @exception IOException if the RMI socket factory is already set
     * @exception  SecurityException  if a security manager exists and its  
     *             <code>checkSetFactory</code> method doesn't allow the operation.
     * @see java.lang.SecurityManager#checkSetFactory()
     * @since JDK1.1
     */
    public synchronized static void setSocketFactory(RMISocketFactory fac)
	throws IOException
    {
    	if (factory != null) {
	    throw new SocketException("factory already defined");
	}
	SecurityManager security = System.getSecurityManager();
	if (security != null) {
	    security.checkSetFactory();
	}
	factory = fac;
    }

    /**
     * Returns the socket factory set by the <code>setSocketFactory</code>
     * method. Returns <code>null</code> if no socket factory has been
     * set.
     * @return the socket factory
     * @see #setSocketFactory(RMISocketFactory)
     * @since JDK1.1
     */
    public synchronized static RMISocketFactory getSocketFactory()
    {
	return factory;
    }

    /**
     * Returns a reference to the default socket factory used
     * by this RMI implementation.  This will be the factory used
     * by the RMI runtime when <code>getSocketFactory</code>
     * returns <code>null</code>.
     * @return the default RMI socket factory
     * @since JDK1.1
     */
    public synchronized static RMISocketFactory getDefaultSocketFactory() {
	if (defaultSocketFactory == null) {
	    defaultSocketFactory =
		new sun.rmi.transport.proxy.RMIMasterSocketFactory();
	}
	return defaultSocketFactory;
    }

    /**
     * Sets the failure handler to be called by the RMI runtime if server
     * socket creation fails.  By default, if no failure handler is installed
     * and server socket creation fails, the RMI runtime does attempt to
     * recreate the server socket.
     * @param fh the failure handler
     * @see java.rmi.server.RMIFailureHandler#failure(Exception)
     * @since JDK1.1
     */
    public synchronized static void setFailureHandler(RMIFailureHandler fh)
    {
	handler = fh;
    }

    /**
     * Returns the handler for socket creation failure set by the
     * <code>setFailureHandler</code> method.
     * @return the failure handler
     * @see #setFailureHandler(RMIFailureHandler)
     * @since JDK1.1
     */
    public synchronized static RMIFailureHandler getFailureHandler()
    {
	return handler;
    }
}