001    /**
002     * hammurapi-rules @mesopotamia.version@
003     * Hammurapi rules engine. 
004     * Copyright (C) 2005  Hammurapi Group
005     *
006     * This program is free software; you can redistribute it and/or
007     * modify it under the terms of the GNU Lesser General Public
008     * License as published by the Free Software Foundation; either
009     * version 2 of the License, or (at your option) any later version.
010     *
011     * This program is distributed in the hope that it will be useful,
012     * but WITHOUT ANY WARRANTY; without even the implied warranty of
013     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014     * Lesser General Public License for more details.
015     *
016     * You should have received a copy of the GNU Lesser General Public
017     * License along with this library; if not, write to the Free Software
018     * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
019     *
020     * URL: http://http://www.hammurapi.biz
021     * e-Mail: support@hammurapi.biz 
022     */
023    package biz.hammurapi.rules;
024    
025    import java.io.Serializable;
026    import java.util.ArrayList;
027    import java.util.Collection;
028    import java.util.HashMap;
029    import java.util.Iterator;
030    import java.util.LinkedHashMap;
031    import java.util.Map;
032    
033    import javax.rules.Handle;
034    
035    import biz.hammurapi.config.Component;
036    import biz.hammurapi.config.ComponentBase;
037    import biz.hammurapi.config.ConfigurationException;
038    
039    /**
040     * Handle manager implementation which keeps handles in memory. 
041     * Objects are compared by identity, not by eqals().
042     * @author Pavel Vlasov
043     * @version ${Revision}
044     */
045    public class IdentityHandleManager extends ComponentBase implements HandleManager, Component {
046            
047            private Map handleMap;
048    
049            private String storageReference;
050            
051            /**
052             * Path to object storage.
053             * @param storageReference
054             */
055            public void setStorageReference(String storageReference) {
056                    this.storageReference = storageReference;
057            }
058            
059    
060            private static class HandleImpl implements Handle, Serializable {
061                    private static final long serialVersionUID = -6198273232968377370L;
062                    private Object master;
063                    
064                                    
065                    HandleImpl(Object master) {
066                            this.master=master;
067                    }
068                    
069                    public boolean equals(Object obj) {
070                            return obj instanceof HandleImpl && master==((HandleImpl) obj).master;
071                    }
072                    
073                    public int hashCode() {
074                            return master==null ? 0 : master.hashCode();
075                    }
076                    
077                    public String toString() {
078                            return getClass().getName() + " -> " + master;
079                    }
080            }
081            
082            synchronized public Handle addObject(Object object) {
083                    Handle newHandle=new HandleImpl(object);
084                    Handle existingHandle=(Handle) handleMap.get(newHandle);
085                    if (existingHandle==null) {
086                            handleMap.put(newHandle, newHandle);
087                            return newHandle;
088                    } 
089                            
090                    return existingHandle;
091            }
092    
093            synchronized public Object getObject(Handle handle) {
094                    if (handle instanceof HandleImpl) {
095                            return ((HandleImpl) handle).master;
096                    } 
097                    
098                    throw new IllegalArgumentException("Foreign handle: "+handle);
099            }
100    
101            public Collection getObjects() {
102                    ArrayList ret=new ArrayList();
103                    Iterator it=handleMap.keySet().iterator();
104                    while (it.hasNext()) {
105                            ret.add(((HandleImpl) it.next()).master);
106                    }
107                    return ret;
108            }
109    
110            public Collection getHandles() {
111                    return handleMap.keySet();
112            }
113            
114            synchronized public void remove(Handle handle) {
115                    handleMap.remove(handle);
116            }
117    
118            public boolean contains(Handle handle) {                
119                    return handleMap.containsKey(handle);
120            }
121    
122            synchronized public void rebind(Handle handle, Object object) {
123                    if (handle instanceof HandleImpl) {
124                            handleMap.remove(handle);
125                            ((HandleImpl) handle).master=object;
126                            handleMap.put(handle, handle);
127                    } else {
128                            throw new IllegalArgumentException("Foreign handle: "+handle);
129                    }
130            }
131    
132            public void remove(Object obj) {
133                    handleMap.remove(new HandleImpl(obj));
134            }
135    
136            public synchronized void clear() {
137                    handleMap.clear();
138            }
139            
140            public void start() throws ConfigurationException {
141                    if (storageReference==null) {
142                            handleMap=new LinkedHashMap();
143                    } else {
144                            handleMap = (Map) ((ObjectStorage) get(storageReference)).get("handle-manager");
145                            if (handleMap==null) {
146                                    handleMap=new HashMap();
147                                    ((ObjectStorage) get(storageReference)).put("handle-manager", handleMap);
148                            }
149                    }
150            }
151    
152            public void stop() throws ConfigurationException {
153                    // Nothing
154            }
155    
156            public synchronized boolean isNegatedBy(Negator negator) {
157                    Iterator it=handleMap.keySet().iterator();
158                    while (it.hasNext()) {
159                            HandleImpl handle=(HandleImpl) it.next();
160                            if (Conclusion.object2Negator(handle.master, negator)) {
161                                    it.remove();
162                            }
163                    }
164                    
165                    return false;
166            }
167    }