rete.java

jboss规则引擎

package org.drools.reteoo;

/*
 * Copyright 2005 JBoss Inc
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

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.RuleBaseConfiguration;
import org.drools.common.DefaultFactHandle;
import org.drools.common.NodeMemory;
import org.drools.spi.ObjectType;
import org.drools.spi.ObjectTypeResolver;
import org.drools.spi.PropagationContext;

/**
 * The Rete-OO network.
 * 
 * The Rete class is the root <code>Object</code>. All objects are asserted into
 * the Rete node where it propagates to all matching ObjectTypeNodes.
 * 
 * The first time an  instance of a Class type is asserted it does a full
 * iteration of all ObjectTyppeNodes looking for matches, any matches are 
 * then cached in a HashMap which is used for future assertions.
 * 
 * While Rete  extends ObjectSource nad implements ObjectSink it nulls the 
 * methods attach(), remove() and  updateNewNode() as this is the root node
 * they are no applicable
 * 
 * @see ObjectTypeNode
 * 
 * @author <a href="mailto:[e-mail]">Mark Proctor</a>
 * @author <a href="mailto:[e-mail]">Bob McWhirter</a>
 */
class Rete extends ObjectSource
    implements
    Serializable,
    ObjectSink,
    NodeMemory {
    // ------------------------------------------------------------
    // Instance members
    // ------------------------------------------------------------

    /**
     * 
     */
    private static final long        serialVersionUID = -7166421271509211041L;
    /** The <code>Map</code> of <code>ObjectTypeNodes</code>. */
    private final Map                objectTypeNodes  = new HashMap();
    private ObjectTypeNode           lastAddedNode    = null;

    private final ObjectTypeResolver resolver;

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

    /**
     * Construct.
     */
    public Rete() {
        this( null );
    }

    public Rete(final ObjectTypeResolver resolver) {
        super( 0 );
        this.resolver = resolver;
    }

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

    /**
     * This is the entry point into the network for all asserted Facts. Iterates a cache
     * of matching <code>ObjectTypdeNode</code>s asserting the Fact. If the cache does not
     * exist it first iteraes and builds the cache.
     * 
     * @param handle
     *            The FactHandle of the fact to assert
     * @param context
     *            The <code>PropagationContext</code> of the <code>WorkingMemory</code> action   
     * @param workingMemory
     *            The working memory session.
     */
    public void assertObject(final DefaultFactHandle handle,
                             final PropagationContext context,
                             final ReteooWorkingMemory workingMemory) {
        final HashMap memory = (HashMap) workingMemory.getNodeMemory( this );

        final Object object = handle.getObject();

        ObjectTypeNode[] cachedNodes = (ObjectTypeNode[]) memory.get( object.getClass() );
        if ( cachedNodes == null ) {
            cachedNodes = getMatchingNodes( object );
            memory.put( object.getClass(),
                        cachedNodes );
        }

        for ( int i = 0, length = cachedNodes.length; i < length; i++ ) {
            cachedNodes[i].assertObject( 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.
     */
    public void retractObject(final DefaultFactHandle handle,
                              final PropagationContext context,
                              final ReteooWorkingMemory workingMemory) {
        final HashMap memory = (HashMap) workingMemory.getNodeMemory( this );

        final Object object = handle.getObject();

        ObjectTypeNode[] cachedNodes = (ObjectTypeNode[]) memory.get( object.getClass() );
        if ( cachedNodes == null ) {
            cachedNodes = getMatchingNodes( object );
            memory.put( object.getClass(),
                        cachedNodes );
        }

        for ( int i = 0; i < cachedNodes.length; i++ ) {
            cachedNodes[i].retractObject( handle,
                                          context,
                                          workingMemory );
        }
    }

    public void modifyObject(final DefaultFactHandle handle,
                             final PropagationContext context,
                             final ReteooWorkingMemory workingMemory) {
        final HashMap memory = (HashMap) workingMemory.getNodeMemory( this );

        final Object object = handle.getObject();

        ObjectTypeNode[] cachedNodes = (ObjectTypeNode[]) memory.get( object.getClass() );
        if ( cachedNodes == null ) {
            cachedNodes = getMatchingNodes( object );
            memory.put( object.getClass(),
                        cachedNodes );
        }

        for ( int i = 0; i < cachedNodes.length; i++ ) {
            cachedNodes[i].modifyObject( handle,
                                         context,
                                         workingMemory );
        }
    }

    private ObjectTypeNode[] getMatchingNodes(final Object object) throws FactException {
        final List cache = new ArrayList();

        for ( final Iterator it = objectTypeNodeIterator(); it.hasNext(); ) {
            final ObjectTypeNode node = (ObjectTypeNode) it.next();
            if ( node.matches( object ) ) {
                cache.add( node );
            }
        }
        return (ObjectTypeNode[]) cache.toArray( new ObjectTypeNode[cache.size()] );
    }

    /**
     * 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 objectTypeNodeIterator() {
        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(final ObjectType objectType) {
        return (ObjectTypeNode) this.objectTypeNodes.get( objectType );
    }

    /**
     * Add an <code>ObjectTypeNode</code> child to this <code>Rete</code>.
     * 
     * @param node
     *            The node to add.
     */
    private void addObjectTypeNode(final ObjectTypeNode node) {
        this.lastAddedNode = 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(final ObjectSink objectSink) {
        addObjectTypeNode( (ObjectTypeNode) objectSink );
    }

    protected void removeObjectSink(final ObjectSink objectSink) {
        this.objectTypeNodes.remove( objectSink );
    }

    public void attach() {
        // do nothing this is the root node
    }

    public void attach(final ReteooWorkingMemory[] workingMemories) {
        // do nothing this is the root node        
    }

    // when a new ObjectTypeNode is added, check for possible 
    // propagations into the new node
    public void updateNewNode(final ReteooWorkingMemory workingMemory,
                              final PropagationContext context) {
        if ( this.lastAddedNode != null ) {
            final ObjectType objType = this.lastAddedNode.getObjectType();
            for ( final Iterator i = workingMemory.getFactHandleMap().entrySet().iterator(); i.hasNext(); ) {
                final Map.Entry entry = (Map.Entry) i.next();
                final DefaultFactHandle handle = (DefaultFactHandle) entry.getValue();
                if ( objType.matches( handle.getObject() ) ) {
                    this.lastAddedNode.assertObject( handle,
                                                     context,
                                                     workingMemory );
                }
            }
            this.lastAddedNode = null;
        }
    }

    public void remove(final BaseNode node,
                       final ReteooWorkingMemory[] workingMemories) {
        final ObjectTypeNode objectTypeNode = (ObjectTypeNode) node;
        removeObjectSink( objectTypeNode );
        //@todo: we really should attempt to clear the memory cache for this ObjectTypeNode        
    }

    public Object createMemory(final RuleBaseConfiguration config) {
        return new HashMap();
    }

    public int hashCode() {
        return this.objectTypeNodes.hashCode();
    }

    public boolean equals(final Object object) {
        if ( object == this ) {
            return true;
        }

        if ( object == null || object.getClass() != Rete.class ) {
            return false;
        }

        final Rete other = (Rete) object;
        return this.objectTypeNodes.equals( other.objectTypeNodes );
    }

}