helloworldbuilder.java

drools 一个开放源码的规则引擎

package org.drools.reteoo;

/*
 * $Id: HelloWorldBuilder.java,v 1.14 2005/05/08 04:22:34 dbarnett Exp $
 *
 * Copyright 2004-2005 (C) The Werken Company. All Rights Reserved.
 *
 * Redistribution and use of this software and associated documentation
 * ("Software"), with or without modification, are permitted provided that the
 * following conditions are met:
 *
 * 1. Redistributions of source code must retain copyright statements and
 * notices. Redistributions must also contain a copy of this document.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * 3. The name "drools" must not be used to endorse or promote products derived
 * from this Software without prior written permission of The Werken Company.
 * For written permission, please contact [e-mail].
 *
 * 4. Products derived from this Software may not be called "drools" nor may
 * "drools" appear in their names without prior written permission of The Werken
 * Company. "drools" is a registered trademark of The Werken Company.
 *
 * 5. Due credit should be given to The Werken Company.
 * (http://drools.werken.com/).
 *
 * THIS SOFTWARE IS PROVIDED BY THE WERKEN COMPANY AND CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE WERKEN COMPANY OR ITS CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 */

import java.util.Iterator;
import java.util.List;

import org.drools.RuleBase;
import org.drools.rule.Declaration;
import org.drools.rule.Rule;
import org.drools.rule.RuleSet;
import org.drools.spi.Condition;

/**
 * This simple Rete builder and it create a completely unoptimised Rete, ie not
 * JoinNodes, but is an ideal starting point to learn more about how Rete's are
 * built. org.drools.reteoo should be consultated to get a greater undertanding
 * of optimisations
 */

public class HelloWorldBuilder
{
    private final Rete      rete;
    private final Rule[]    rules;

    public HelloWorldBuilder(RuleSet ruleSet)
    {
        this.rete = new Rete( );
        this.rules = ruleSet.getRules( );
    }

    public RuleBase buildRuleBase()
    {
        Declaration declaration;
        Rule rule;
        ParameterNode parameterNode;
        for ( int i = 0; i < rules.length; i++ )
        {
            rule = rules[i];
            for ( Iterator j = rule.getParameterDeclarations( ).iterator( ); j.hasNext( ); )
            {
                declaration = ( Declaration ) j.next();

                parameterNode = new ParameterNode( rete.getOrCreateObjectTypeNode( declaration.getObjectType( ) ),
                                                   declaration );

                parameterNode.attach( );

                List conditions = rule.getConditions( );
                if ( conditions.isEmpty( ) )
                {
                    new TerminalNode( parameterNode, rule );
                }
                else
                {
                    for ( int k = 0; k < conditions.size( ); k++ )
                    {
                        ConditionNode conditionNode = new ConditionNode( rule, parameterNode,
                                                                         ( Condition ) conditions.get( k ) );

                        conditionNode.attach( );

                        new TerminalNode( conditionNode, rule );
                    }
                }
            }
        }

        return new RuleBaseImpl( this.rete );
    }
}