ClientStateStorageImpl

package scm.hivemind.statefulservice;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionBindingListener;

import org.apache.commons.logging.Log;


/**
 * 
 * @author Marcus Schulte
 */
public class ClientStateStorageImpl implements ClientStateStorage {
    protected Log myLog;
    
        private HttpSession session = null;     
        private boolean invalidSession = false;
        private Map clientStores = new HashMap();
        private Map map = new HashMap();
        
        
        private class StoredProxy implements HttpSessionBindingListener {
           private StateStorageClearanceListener clearanceListener;
           
           public StoredProxy ( StateStorageClearanceListener object ){
               clearanceListener = object;
           }
            
        public void valueBound( HttpSessionBindingEvent arg0 ) {
            // TODO Auto-generated method stub
        }
        
        public void valueUnbound( HttpSessionBindingEvent e ) {
            invalidSession = true;
            clearanceListener.clientStateCleared();
            myLog.debug("Session expired or invalidated.");
        }
        
        public StateStorageClearanceListener getObject() {
            return clearanceListener;
        }
        }

        
        /* (non-Javadoc)
         * @see com.bmw.sample.ClientStateStorage#provideSession(javax.servlet.http.HttpSession)
         */
        public void provideSession(HttpSession s ) {
                this.session = s;
                this.invalidSession = false;
        }
        
        public void setLog( Log log ) {
            myLog = log;
        }

        /* (non-Javadoc)
         * @see com.bmw.sample.ClientStateStorage#store(java.lang.String, java.lang.Object)
         */
        public void store(String key, StateStorageClearanceListener obj) {
                if (session==null) {
                    myLog.debug( "storing key: "+key );
                        map.put(key,obj);
                } else {
                    if ( ! invalidSession ) {
                        StoredProxy p = (StoredProxy) session.getAttribute( key );
                        
                        // avoid unbind-events due to replacing an object with itself...
                        if ( p!=null && p.getObject()==obj)
                            return;
                        
                        session.setAttribute( key, new StoredProxy(obj) );
                    } else
                        myLog.debug("skipping store due to invalid Session");
                }
        }

        
        /* (non-Javadoc)
         * @see com.bmw.sample.ClientStateStorage#retrieve(java.lang.String)
         */
        public StateStorageClearanceListener retrieve(String key) {
                if (session == null) {
                    myLog.debug( "retrieving key: "+key );
                        return (StateStorageClearanceListener) map.get(key);
                } else {
                    StoredProxy p = (StoredProxy) session.getAttribute(key);
                    if ( p != null )
                        return p.getObject();
                    else
                        return null;
                }               
        }
        
        /* (non-Javadoc)
         * @see com.bmw.sample.ClientStateStorage#setClientId(java.lang.String)
         */
        public void setClientId(String cid) {
                Map m = (Map) clientStores.get( cid );
                if ( m == null) {
                        m = new HashMap();
                        clientStores.put( cid, m );
                }
                map = m;
        }
        /* (non-Javadoc)
         * @see com.bmw.sample.ClientStateStorage#clear()
         */
        public void clear( String clientId ) {
                Map store = ( (Map)clientStores.get(clientId) );
                for ( Iterator it = store.values().iterator(); it.hasNext(); ) {
            StateStorageClearanceListener obj 
                                                = (StateStorageClearanceListener) it.next();
            obj.clientStateCleared();
        }
                store.clear();
        }

}