这个weblogging 设计得比较精巧

				package org.roller.model;								import org.roller.pojos.UserData;								/**				 * Represents a persistence session; this is the object that a PersistenceStrategy				 * stores in thread local storage.				 * @author David M Johnson				 */				public interface PersistenceSession 				{				    /** Get underlying persistence session object (e.g. a Hibernate Session) */				    public Object getSessionObject();				    				    /** Set underlying persistence session object */				    public void setSessionObject(Object newSession);				    				    /** Get user associated with this session */				    public UserData getUser();				    				    /** Set user assoicated with this session */				    public void setUser(UserData user);				}