adapter4queries_1_1.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.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.jdom.Element;
import org.mandarax.kernel.DerivationEventListener;
import org.mandarax.kernel.Fact;
import org.mandarax.kernel.LogicFactory;
import org.mandarax.kernel.Query;
import org.mandarax.zkb.ObjectPersistencyService;
import org.mandarax.zkb.ZKBException;
/**
 * An adapter class for queries.
 * @see org.mandarax.kernel.Query
 * @author <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</A>
 * @version 3.4 <7 March 05>
 * @since 2.3
 */

public class Adapter4Queries_1_1 extends AbstractAdapter {

/**
 * 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 XKBException is thrown if export fails
 */
public Element exportObject(Object obj,GenericDriver driver,ObjectPersistencyService ops) throws  ZKBException {
      check(obj,Query.class);
      Query query = (Query)obj;
      Element e = new Element(QUERY);
      String queryName = query.getName();
      if (queryName==null) queryName = "";
      e.setAttribute(NAME,queryName);
      Fact[] queryFacts = query.getFacts();
      for (int i=0;i<queryFacts.length;i++) {
            Element el = exportObject(queryFacts[i],TagAndAttributeNames.FACT,driver,ops);
            e.addContent(el);
      }
	  exportProperties(e,query);
	  // new in 3.2 : add derivation event listeners
	 DerivationEventListener[] listeners = query.getDerivationEventListeners();
	 if (listeners!=null) {
	 	for (int i=0;i<listeners.length;i++) {
	 		Element el = exportObject(listeners[i],TagAndAttributeNames.DERIVATION_LISTENER,driver,ops);
			e.addContent(el);
	 	}
	 }
     return e;
}
/**
 * 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 XKBException is thrown if import fails
 */
public Object importObject(Element e,GenericDriver driver,ObjectPersistencyService ops,LogicFactory lfactory) throws ZKBException {
      List list = new ArrayList();
      Adapter adapter4Facts = null;
      List children = e.getChildren(FACT);
      for (Iterator it = children.iterator();it.hasNext();) {
              Element eFact = (Element)it.next();
              if (adapter4Facts==null) adapter4Facts = driver.getAdapter(eFact.getName());
              Fact queryFact = (Fact)adapter4Facts.importObject(eFact,driver,ops,lfactory);
		list.add(queryFact);
      }
      Fact[] facts = new Fact[list.size()];
      for (int i=0;i<list.size();i++) facts[i]=(Fact)list.get(i);
	  String queryName = e.getAttributeValue(NAME);
	  
	  // new in 3.2 support for derivation listeners
	  list.clear();
	  children = e.getChildren(DERIVATION_LISTENER);
	  Adapter adapter4Listeners = null;
	  for (Iterator it = children.iterator();it.hasNext();) {
				Element eListeners = (Element)it.next();
				if (adapter4Listeners==null) adapter4Listeners = driver.getAdapter(eListeners.getName());
				DerivationEventListener l = (DerivationEventListener)adapter4Listeners.importObject(eListeners,driver,ops,lfactory);
				if (l==null) LOG_ZKB.warn("Problem importing derivation event listeners, check sourcecode and classpath");
			    else list.add(l);
	  }
	  DerivationEventListener[] listeners = new DerivationEventListener[list.size()];
	  for (int i=0;i<list.size();i++) listeners[i]=(DerivationEventListener)list.get(i);
		
      // build query
      Query q = lfactory.createQuery(facts,queryName==null?"":queryName);
      if (queryName==null) q.setName(q.toString());
      q.setDerivationEventListeners(listeners);
	  importProperties(e,q);
      return q;
}
/**
 * Get the name of the associated tag (element).
 * @return a string
 */
public String getTagName() {
      return QUERY;
}
/**
 * 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 query (atom*,properties?)>\n");
	out.append("<!ATTLIST query name CDATA #REQUIRED>\n");
}

}