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();
	}

}