/* Authenticator.java -- Abstract class for obtaining authentication info
   Copyright (C) 1998,2000 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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any later version.
 
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WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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02111-1307 USA.

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making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
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this exception to your version of the library, but you are not
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exception statement from your version. */

package java.net;

/**
  * Sometimes a network operation (such as hitting a password protected
  * web site) will require authentication information in the form of a
  * username and password.  This abstract class provides a model for 
  * obtaining that information.
  * <p>
  * To make use of this feature, a programmer must create a subclass of
  * Authenticator that knows how to obtain the necessary info.  An example
  * would be a class that popped up a dialog box to prompt the user.  
  * After creating an instance of that subclass, the static setDefault
  * method of this class is called to set up that instance as the object
  * to use on subsequent calls to obtain authorization.
  *
  * @since 1.2
  *
  * @author Aaron M. Renn (arenn@urbanophile.com)
  */
public abstract class Authenticator
{

/*************************************************************************/

/*
 * Class Variables
 */

/**
  * This is the default Authenticator object to use for password requests
  */
private static Authenticator default_authenticator;

/*************************************************************************/

/*
 * Instance Variables
 */

/**
  * InternetAddress of the site requesting authentication
  */
private InetAddress addr;

/**
  * The port number of the site requesting authentication
  */
private int port;

/**
  * The protocol name of the site requesting authentication
  */
private String protocol;

/**
  * The prompt to display to the user when requesting authentication info
  */
private String prompt;

/**
  * The authentication scheme in use
  */
private String scheme;

/*************************************************************************/

/*
 * Class Methods
 */

/**
  * This method sets the default <code>Authenticator</code> object (an 
  * instance of a
  * subclass of <code>Authenticator</code>) to use when prompting the user for
  * information.  Note that this method checks to see if the caller is
  * allowed to set this value (the "setDefaultAuthenticator" permission)
  * and throws a <code>SecurityException</code> if it is not.
  *
  * @param def_auth The new default <code>Authenticator</code> object to use
  *
  * @exception SecurityException If the caller does not have permission 
  * to perform this operation
  */ 
public static void
setDefault(Authenticator def_auth)
{
  SecurityManager sm = System.getSecurityManager();
  if (sm != null)
    sm.checkPermission(new NetPermission("setDefaultAuthenticator"));

  default_authenticator = def_auth;
} 

/*************************************************************************/

/**
  * This method is called whenever a username and password for a given
  * network operation is required.  First, a security check is made to see
  * if the caller has the "requestPasswordAuthentication"
  * permission.  If not, the method thows an exception.  If there is no
  * default <code>Authenticator</code> object, the method then returns 
  * <code>null</code>.  Otherwise, the default authenticators's instance 
  * variables are initialized and it's <code>getPasswordAuthentication</code>
  *  method is called to get the actual authentication information to return.
  *
  * @param addr The address requesting authentication
  * @param port The port requesting authentication
  * @param protocol The protocol requesting authentication
  * @param prompt The prompt to display to the user when requesting 
           authentication info
  * @param scheme The authentication scheme in use
  * 
  * @return A <code>PasswordAuthentication</code> object with the user's 
  *         authentication info.
  *
  * @exception SecurityException If the caller does not have permission to 
  *         perform this operation
  */ 
public static PasswordAuthentication
requestPasswordAuthentication(InetAddress addr, int port, String protocol,
                              String prompt, String scheme) 
{
  SecurityManager sm = System.getSecurityManager();
  if (sm != null)
    sm.checkPermission(new NetPermission("requestPasswordAuthentication"));

  if (default_authenticator == null)
    return(null);

  default_authenticator.addr = addr;
  default_authenticator.port = port;
  default_authenticator.protocol = protocol;
  default_authenticator.prompt = prompt;
  default_authenticator.scheme = scheme;

  return(default_authenticator.getPasswordAuthentication());
}

/*************************************************************************/

/*
 * Constructors
 */

/**
  * Default, no-argument constructor for subclasses to call.
  */
public
Authenticator()
{
}

/*************************************************************************/

/*
 * Instance Methods
 */

/**
  * This method returns the address of the site that is requesting
  * authentication.
  *
  * @return The requesting site
  */
protected final InetAddress
getRequestingSite()
{
  return(addr);
}

/*************************************************************************/

/**
  * This method returns the port of the site that is requesting 
  * authentication.
  *
  * @return The requesting port
  */
protected final int
getRequestingPort()
{
  return(port);
}

/*************************************************************************/

/**
  * This method returns the requesting protocol of the operation that is
  * requesting authentication
  *
  * @return The requesting protocol
  */
protected final String
getRequestingProtocol()
{
  return(protocol);
}

/*************************************************************************/

/**
  * Returns the prompt that should be used when requesting authentication 
  * information from the user
  * 
  * @return The user prompt
  */
protected final String
getRequestingPrompt()
{
  return(prompt);
}

/*************************************************************************/

/**
  * This method returns the authentication scheme in use
  *
  * @return The authentication scheme
  */
protected final String
getRequestingScheme()
{
  return(scheme);
}

/*************************************************************************/

/**
  * This method is called whenever a request for authentication is made.  It
  * can call the other getXXX methods to determine the information relevant
  * to this request.  Subclasses should override this method, which returns
  * <code>null</code> by default.
  *
  * @return The PasswordAuthentication information
  */
protected PasswordAuthentication
getPasswordAuthentication()
{
  return(null);
}

} // class Authenticator