rete.java

drools 一个开放源码的规则引擎

package org.drools.reteoo;

/*
 * $Id: Rete.java,v 1.6 2005/08/14 22:44:12 mproctor Exp $
 *
 * Copyright 2001-2003 (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 trademark of The Werken Company.
 *
 * 5. Due credit should be given to The Werken Company. (http://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.io.Serializable;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.drools.FactException;
import org.drools.rule.Rule;
import org.drools.spi.ObjectType;
import org.drools.spi.PropagationContext;

/**
 * The Rete-OO network.
 * 
 * This node accepts an <code>Object</code>, and simply propagates it to all
 * <code>ObjectTypeNode</code> s for type testings.
 * 
 * @see ObjectTypeNode
 * 
 * @author <a href="mailto:[e-mail]">bob mcwhirter </a>
 */
class Rete extends ObjectSource
    implements
    Serializable,
    ObjectSink
{
    // ------------------------------------------------------------
    // Instance members
    // ------------------------------------------------------------

    /** The set of <code>ObjectTypeNodes</code>. */
    private final Map objectTypeNodes = new HashMap( );    
    
    private final List rulesToUpdate = new ArrayList( );

    // ------------------------------------------------------------
    // Constructors
    // ------------------------------------------------------------

    /**
     * Construct.
     */
    public Rete()
    {
        super( 0 );
    }

    // ------------------------------------------------------------
    // Instance methods
    // ------------------------------------------------------------

    /**
     * Assert a new fact object into this <code>RuleBase</code> and the
     * specified <code>WorkingMemory</code>.
     * 
     * @param handle
     *            The fact handle.
     * @param object
     *            The object to assert.
     * @param workingMemory
     *            The working memory session.
     * 
     * @throws FactException
     *             if an error occurs during assertion.
     */
    public void assertObject(Object object,
                             FactHandleImpl handle,
                             PropagationContext context,
                             WorkingMemoryImpl workingMemory) throws FactException
    {
        Iterator nodeIter = getObjectTypeNodeIterator( );

        while ( nodeIter.hasNext( ) )
        {
            ((ObjectTypeNode) nodeIter.next( )).assertObject( object,
                                                              handle,
                                                              context,
                                                              workingMemory );
        }
    }

    /**
     * Retract a fact object from this <code>RuleBase</code> and the specified
     * <code>WorkingMemory</code>.
     * 
     * @param handle
     *            The handle of the fact to retract.
     * @param workingMemory
     *            The working memory session.
     * 
     * @throws FactException
     *             if an error occurs during retraction.
     */
    public void retractObject(FactHandleImpl handle,
                              PropagationContext context,
                              WorkingMemoryImpl workingMemory) throws FactException
    {
        Iterator nodeIter = getObjectTypeNodeIterator( );

        while ( nodeIter.hasNext( ) )
        {
            ((ObjectTypeNode) nodeIter.next( )).retractObject( handle,
                                                               context,
                                                               workingMemory );
        }
    }


    /**
     * Retrieve all <code>ObjectTypeNode</code> children of this node.
     * 
     * @return The <code>Set</code> of <code>ObjectTypeNodes</code>.
     */
    Collection getObjectTypeNodes()
    {
        return this.objectTypeNodes.values( );
    }

    /**
     * Retrieve an <code>Iterator</code> over the <code>ObjectTypeNode</code>
     * children of this node.
     * 
     * @return An <code>Iterator</code> over <code>ObjectTypeNodes</code>.
     */
    Iterator getObjectTypeNodeIterator()
    {
        return this.objectTypeNodes.values( ).iterator( );
    }

    /**
     * Retrieve an <code>ObjectTypeNode</code> keyed by
     * <code>ObjectType</code>.
     * 
     * @param objectType
     *            The <code>ObjectType</code> key.
     * 
     * @return The matching <code>ObjectTypeNode</code> if one has already
     *         been created, else <code>null</code>.
     */
    ObjectTypeNode getObjectTypeNode(ObjectType objectType)
    {
        return (ObjectTypeNode) this.objectTypeNodes.get( objectType );
    }

    /**
     * Retrieve an <code>ObjectTypeNode</code> keyed by
     * <code>ObjectType</code>, creating one, if necessary.
     * 
     * @param objectType
     *            The <code>ObjectType</code> key.
     * 
     * @return The matching <code>ObjectTypeNode</codeb>.
     */
    ObjectTypeNode getOrCreateObjectTypeNode(ObjectType objectType)
    {
        ObjectTypeNode node = getObjectTypeNode( objectType );

        if ( node == null )
        {
            node = new ObjectTypeNode( 0,
                                       objectType,
                                       this );

            node.attach( );
        }

        this.rulesToUpdate.add( node );

        return node;
    }

    /**
     * Add an <code>ObjectTypeNode</code> child to this <code>Rete</code>.
     * 
     * @param node
     *            The node to add.
     */
    private void addObjectTypeNode(ObjectTypeNode node)
    {
        this.objectTypeNodes.put( node.getObjectType( ),
                                  node );
    }
    
    /**
     * Adds the <code>TupleSink</code> so that it may receive
     * <code>Tuples</code> propagated from this <code>TupleSource</code>.
     * 
     * @param tupleSink
     *            The <code>TupleSink</code> to receive propagated
     *            <code>Tuples</code>.
     */
    protected void addObjectSink(ObjectSink objectSink)
    {
        addObjectTypeNode( (ObjectTypeNode) objectSink );
    }

    public void attach()
    {
        // do nothing this is the root node
    }
    
    void addRule(Rule rule)
    {
        
    }
    
    void updateWorkingMemory(WorkingMemoryImpl workingMemory) throws FactException
    {
        Iterator it = this.rulesToUpdate.iterator();
        ObjectTypeNode node = null;
        PropagationContext context = new PropagationContextImpl( PropagationContext.ASSERTION, 
                                                             null, 
                                                             null );
        while( it.hasNext() )
        {            
            node =  ( ObjectTypeNode ) it.next();
            node.updateNewRule( workingMemory,
                                context );
        }          
    }
    
    void ruleAdded()
    {
        Iterator it = this.rulesToUpdate.iterator();
        ObjectTypeNode node = null;

        while( it.hasNext() )
        {
            node = ( ObjectTypeNode ) it.next();
            node.ruleAttached();
            it.remove();
        }         
    }
    
}