expressionevaluator.java

iiitAccessServer是一个用Java编写的基于规则的企业鉴别系统。它作为一个服务器工作

/*******************************************************************************
 * Copyright (C) 2002, 2003
 * ingenieurbuero fuer innovative informationstechnik (iiit)
 * Dipl.-Ing. Joerg Beckmann, Dortmund, Germany
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but 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.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * version $Id: ExpressionEvaluator.java,v 1.5 2003/04/13 21:09:56 joerg Exp $
 ******************************************************************************/

package de.iiit.access.server;

import de.iiit.access.common.api.*;

import de.iiit.access.server.api.*;
import de.iiit.access.server.plugins.parser.*;

import de.iiit.cache.*;

import java.util.*;

/** This class evaluates expression. It can be used by server plug-ins
 * like TcpServer to evaluate the expression received from a client.
 * @version $Revision: 1.5 $ $Date: 2003/04/13 21:09:56 $
 */
public class ExpressionEvaluator
{
    /** CVS Version Tag */
    private static final String vcid = "$Id: ExpressionEvaluator.java,v 1.5 2003/04/13 21:09:56 joerg Exp $";
    
    private static CachePluginIf    cache  = null;
    private Parser parser = new Parser();
    
    /** Creates a new instance of ExpressionResolver */
    public ExpressionEvaluator()
    {
        if (cache == null)
            cache = AccessServer.getCachePlugin();
    }
    
    /** Evaluates one expression.
     * @param name The name of the user for whom the expression shall be evaluated
     * @param expression The expression to evaluate
     * @throws ParserException This exception is thrown if there is something wrong
     * with the expression. The most common cases are syntax errors or
     * circular references within the expression.
     * @return true if the user is member of the set described by the expression and false
     * otherwise.
     */    
    public boolean evaluateExpression(String name, String expression) throws ParserException
    {
        boolean answer = false;
        
        if (cache != null)
        {
            try
            {
                answer = cache.getUserRight(name, expression);
            }
            catch(CacheFaultException e)
            {
                Set s = parser.evaluateExpression(expression, name);

                answer = (s != null && s.contains(name));
            
                cache.addUserRight(name, expression, answer);
            }
        }
        else
        {
            Set s = parser.evaluateExpression(expression, name);

            answer = (s != null && s.contains(name));
        }
        
        return answer;
    }
}

/**
 * $Log: ExpressionEvaluator.java,v $
 * Revision 1.5  2003/04/13 21:09:56  joerg
 * Package structure modified
 *
 * Revision 1.4  2003/04/13 20:28:01  joerg
 * Package structure modified
 *
 * Revision 1.3  2003/04/13 20:16:41  joerg
 * Package structure modified
 *
 * Revision 1.2  2003/01/01 21:04:17  joerg
 * Copyright-Statement aktualisiert
 *
 * Revision 1.1  2002/12/19 15:24:23  joerg
 * Reparatur des CVS-Repositories
 *
 * Revision 1.10  2002/12/09 19:29:17  joerg
 * Versionsdaten in allen JavaDoc-Klassenbeschreibungen ergaenzt
 *
 * Revision 1.9  2002/12/09 16:32:26  joerg
 * JavaDoc Kommentare ergaenzt
 *
 * Revision 1.8  2002/11/27 16:42:26  joerg
 * Parameteruebergabe geaendert, um circulaere Recursion
 * zu erkennen
 *
 * Revision 1.7  2002/11/26 14:40:05  joerg
 * Kleine Optimierungen
 *
 * Revision 1.6  2002/11/26 10:56:13  joerg
 * Package exprparser durch parser erstzt.
 *
 * Revision 1.5  2002/11/20 11:09:12  joerg
 * ParserExceptions werden jetzt durchgereicht
 * Benutzung des Caches ist jetzt optional
 * Fehler beseitigt
 *
 * Revision 1.4  2002/11/19 20:25:18  joerg
 * Cache-Zugriffe nutzen jetzt das Plugin
 *
 * Revision 1.3  2002/11/17 22:06:21  joerg
 * Initialisierung des NameResolvers entfernt.
 *
 * Revision 1.2  2002/11/06 11:11:05  joerg
 * Von Singelton auf 'normales' Object umgestellt
 *
 * Revision 1.1  2002/11/04 09:38:09  joerg
 * Klasse ExpressionResolver ins Package AccessServer verschoben
 * und in ExpressionEvaluator umbenannt.
 *
 * Revision 1.1  2002/11/03 21:55:42  joerg
 * Neue Klasse fuer Thread-sichere Aufloesung von Ausdruecken.
 *
 */