adapter4knowledgebases.java

Mandarax是一个规则引擎的纯Java实现。它支持多类型的事实和基于反映的规则

package org.mandarax.zkb.framework;

/**
 *  Copyright (C) 1999-2004  Jens Dietrich (mailto:[e-mail])
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  This library 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
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

import java.io.PrintWriter;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;

import org.jdom.Comment;
import org.jdom.Element;
import org.mandarax.kernel.ClauseSet;
import org.mandarax.kernel.ExtendedKnowledgeBase;
import org.mandarax.kernel.Fact;
import org.mandarax.kernel.KnowledgeBase;
import org.mandarax.kernel.LogicFactory;
import org.mandarax.kernel.Query;
import org.mandarax.kernel.Rule;
import org.mandarax.sql.SQLClauseSet;
import org.mandarax.zkb.ObjectPersistencyService;
import org.mandarax.zkb.ZKBException;
/**
 * An adapter class for knowledge bases.
 * @see org.mandarax.kernel.KnowledgeBase
 * @author <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</A>
 * @version 3.4 <7 March 05>
 * @since 2.2
 */

public class Adapter4KnowledgeBases extends AbstractAdapter {

	// constant for comparator attribute
	
/**
 * Export an object, i.e., convert it to an element in the DOM.
 * @param obj an object
 * @param driver the generic driver
 * @param ops the object persistency service
 * @exception a ZKBException is thrown if export fails
 */
public Element exportObject(Object obj,GenericDriver driver,ObjectPersistencyService ops) throws ZKBException {
      check(obj,KnowledgeBase.class);
      int ftl = driver.getFaultToleranceLevel();
      PrintWriter out = driver.getLogWriter();
      KnowledgeBase kb = (KnowledgeBase)obj;
      Element e = new Element(RULE_BASE);
      
      e.setAttribute(CLASS,kb.getClass().getName());
      
      // export comparator
      if (kb instanceof ExtendedKnowledgeBase) {
      		Comparator comp = ((ExtendedKnowledgeBase)kb).getComparator();
      		if (comp !=null) {
      			e.addContent(exportObject(comp,COMPARATOR,driver,ops));
      		}      		
      }
      
      // export knowledge
      List clauseSets = kb.getClauseSets();
      for (Iterator it = clauseSets.iterator();it.hasNext();) {
            ClauseSet cs = (ClauseSet)it.next();
            String kindOfObject = getClauseSetType(cs);
            if (kindOfObject==null)  {
                  String msg = "Cannot figure out what kind of clause set the following object is: " + cs;
                  if (ftl==GenericDriver.LOW_FAULT_TOLERANCE) throw new ZKBException(msg);
                  // do nothing if (ftd==driver.HIGH_FAULT_TOLERANCE)
                  else {
                        out.println("Warning");
                        out.println(msg);
                        out.println("The clause is ignored");
                        LOG_XKB.warn(msg);
                        LOG_XKB.warn("The clause is ignored");
                  }
            }
            else {
                  try{
                        Element el = exportObject(cs,kindOfObject,driver,ops);
                        e.addContent(el);
                  }
                  catch (ZKBException x) {
                        String msg = "Problems exporting the knowledge base, export failed for " + cs;
                        if (ftl==GenericDriver.LOW_FAULT_TOLERANCE) throw new ZKBException(msg);
                        // do nothing if (ftd==driver.HIGH_FAULT_TOLERANCE)
                        else {
                              out.println(msg);
                              out.println("See log for details");
                              e.addContent(new Comment(msg));
                              LOG_XKB.error(msg,x);
                        }
                  }

            }
      }
      // export queries
      for (Iterator it = kb.queryNames();it.hasNext();) {
  		  Query q = kb.getQuery((String)it.next());
	      try{
                Element el = exportObject(q,GenericDriver.QUERY,driver,ops);
                e.addContent(el);
          }
          catch (ZKBException x) {
                String msg = "Problems exporting the knowledge base, export failed for query " + q;
                if (ftl==GenericDriver.LOW_FAULT_TOLERANCE) throw new ZKBException(msg);
                // do nothing if (ftd==driver.HIGH_FAULT_TOLERANCE)
                else {
                      out.println(msg);
                      out.println("See log for details");
                      e.addContent(new Comment(msg));
                      LOG_XKB.error(msg,x);
                }
          }
      }
      return e;
}
/**
 * Get the type of clause set, e.g. GenericDriver.FACT or GenericDriver.RULE.
 * @param cs a clause set
 * @return a string
 */
protected String getClauseSetType(ClauseSet cs) {
      if (cs instanceof Rule) return RULE;
      else if (cs instanceof Fact) return FACT;
      else if (cs instanceof SQLClauseSet) return SQL_CLAUSE_SET;
      else return CUSTOM_CLAUSE_SET;
}
/**
 * Build an object from an XML element.
 * @param e an element
 * @param driver the generic driver
 * @param ops the object persistency service
 * @param lfactory the logic factory used to create objects
 * @exception a ZKBException is thrown if export fails
 */
public Object importObject(Element e,GenericDriver driver,ObjectPersistencyService ops,LogicFactory lfactory) throws ZKBException {
       // try to instanciate saved class
       KnowledgeBase kb = null;
       String implClassName = e.getAttributeValue(CLASS);
       if (implClassName !=null) {
       		try {
       			Class implClass = Class.forName(implClassName);
       			kb = (KnowledgeBase)implClass.newInstance();
       		}	
       		catch (ClassNotFoundException x) {
       			LOG_ZKB.error("Cannot find class " + implClassName + ", will use default",x);
       		} 
       		catch (IllegalAccessException x) {
       			LOG_ZKB.error("Cannot instanciate class " + implClassName + ", will use default",x);
       		} 
       		catch (InstantiationException x) {
       			LOG_ZKB.error("Cannot instanciate class " + implClassName + ", will use default",x);
       		} 
       }
       if (kb==null) kb = new org.mandarax.reference.AdvancedKnowledgeBase();
       
       
       int ftl = driver.getFaultToleranceLevel();
       PrintWriter out = driver.getLogWriter();
       List children = e.getChildren();
       for (Iterator it = children.iterator();it.hasNext();) {
            Element child = (Element)it.next();
            Adapter adapter = driver.getAdapter(child.getName());
            if (child.getName().equals(COMPARATOR)) {
            	Comparator comp = (Comparator)adapter.importObject(child,driver,ops,lfactory);
            	if (kb instanceof ExtendedKnowledgeBase) ((ExtendedKnowledgeBase)kb).setComparator(comp);
            }
            else {
	            try {
	                  Object obj = adapter.importObject(child,driver,ops,lfactory);
	                  if (obj instanceof ClauseSet) kb.add((ClauseSet)obj);
	                  else if (obj instanceof Query) kb.addQuery((Query)obj);
	                  else throw new ZKBException("Can only import clause sets and queries into repository, import for object failed: " + obj);
	            }
	            catch (ZKBException x) {
	                  String msg = "Problems importing the knowledge base, import failed for element " + e.getText();
	                  if (ftl==GenericDriver.LOW_FAULT_TOLERANCE) throw new ZKBException(msg);
	                  // do nothing if (ftd==driver.HIGH_FAULT_TOLERANCE)
	                  else {
	                        out.println(msg);
	                        out.println("See log for details");
	                        LOG_XKB.error(msg,x);
	                  }
	            }
            }
       }
       return kb;
}
/**
 * Get the name of the associated tag (element).
 * @return a string
 */
public String getTagName() {
      return RULE_BASE;
}
/**
 * Get the kind of object the adapter can export/import.
 * @return a string
 */
public String getKindOfObject() {
      return RULE_BASE;
}
/**
 * Print the DTD associated with this adapter on a string buffer.
 * @param out the buffer to print on. 
 */
public void printDTD(StringBuffer out) {
	out.append("<!ELEMENT rulebase (comparator?,(atom|rule|sql_clause_set|custom_clause_set|query)*)>\n");
	out.append("<!ATTLIST rulebase class CDATA #IMPLIED>\n");
}


}