adapter4rules_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.Fact;
import org.mandarax.kernel.LogicFactory;
import org.mandarax.kernel.Prerequisite;
import org.mandarax.kernel.Rule;
import org.mandarax.zkb.ObjectPersistencyService;
import org.mandarax.zkb.ZKBException;
/**
 * An adapter class for rules.
 * @see org.mandarax.kernel.Rule
 * @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 Adapter4Rules_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 ZKBException is thrown if export fails
 */
public Element exportObject(Object obj,GenericDriver driver,ObjectPersistencyService ops) throws  ZKBException {
      check(obj,Rule.class);
      Rule rule = (Rule)obj;
      Element e = new Element(RULE);
	  Element eIf = new Element(IF);
	  e.addContent(eIf);
      eIf.setAttribute(CONNECTIVE,rule.isBodyOrConnected()?OR:AND);
      for (Iterator it = rule.getBody().iterator();it.hasNext();) {
            Element el = exportObject(it.next(),PREREQUISITE,driver,ops);
		eIf.addContent(el);
      }
	  Element eThen = new Element(THEN);
	  e.addContent(eThen);
      Element el = exportObject(rule.getHead(),TagAndAttributeNames.FACT,driver,ops);
      eThen.addContent(el);
	  exportProperties(e,rule);
      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 ZKBException is thrown if import fails
 */
public Object importObject(Element e,GenericDriver driver,ObjectPersistencyService ops,LogicFactory lfactory) throws ZKBException {
      // get  body
      Element eIf = e.getChild(IF);
      boolean isOrConnected = OR.equals(eIf.getAttributeValue(CONNECTIVE));
      List body = new ArrayList();
      Adapter adapter4Prereq = driver.getAdapter(PREREQUISITE);
      List children = eIf.getChildren();
      for (Iterator it = children.iterator();it.hasNext();) {
              Element eFact = (Element)it.next();
              Prerequisite premisse = (Prerequisite)adapter4Prereq.importObject(eFact,driver,ops,lfactory);
              body.add(premisse);
      }
      // get head
      Element eThen = e.getChild(THEN);
      Fact head = (Fact)importChild(eThen,FACT,driver,ops,lfactory);

      // build rule
	  Rule rule = lfactory.createRule(body,head,isOrConnected);
	  importProperties(e,rule);
	  return rule;
}
/**
 * Get the name of the associated tag (element).
 * @return a string
 */
public String getTagName() {
      return RULE;
}
/**
 * Print the DTD associated with this adapter on a string buffer.
 * @param out the buffer to print on. 
 */
public void printDTD(StringBuffer out) {
	// warning : properties are declared here and only here
	// this is sensitive w.r.t. the order in which adapters are registered
	// here we assume that this is the first adapter registered that needs property support
	out.append("<!ELEMENT rule (if,then,properties?)>\n");
	out.append("<!ELEMENT if (prereq*)>\n");
	out.append("<!ATTLIST if connective (and | or) \"and\">\n");
	out.append("<!ELEMENT then (atom)>\n");
	out.append("<!ELEMENT properties (property*)>\n");
	out.append("<!ELEMENT property EMPTY>\n");
	out.append("<!ATTLIST property key CDATA #REQUIRED>\n");
	out.append("<!ATTLIST property value CDATA #REQUIRED>\n");
}

}