使用模板方法模式+私有内部类+匿名类解决各个方法间代码结构类似的问题。

package org.hibernate.dao;

import java.io.Serializable;

import org.hibernate.*;
import org.hibernate.entity.*;
//使用模板方法模式+私有内部类+匿名类解决各个方法间代码结构类似的问题。
public class UserDAOImpl implements UserDAO {
	private abstract class UserDAOTemplate{
		abstract protected Object operateSession(Session session,Object arg);
		final public Object operateSessionInTransaction(Object arg){
			Object result=null;
			Session session= HibernateUtil.getSession();	
			Transaction tx = session.beginTransaction();	
			try{
				result=operateSession(session,arg);						
				tx.commit();								
			} catch(Exception e){
				e.printStackTrace();
				tx.rollback();
				result=null;
			}finally{
				HibernateUtil. closeSession();				
			}
			return result;
		}
	}
	public void save(User user){
		new UserDAOTemplate(){
			protected Object operateSession(Session session,Object arg){
				session.save(arg);	
				return null;
			}
		}.operateSessionInTransaction(user);
	}
	
	public User findById(int id){	 
		User user=null;
		user=(User)new UserDAOTemplate(){
			protected Object operateSession(Session session,Object arg){
				return session.get(User.class,(Serializable)arg);		
			}
		}.operateSessionInTransaction(id);
		return user;	
	}
	
	public void delete(User user){
		new UserDAOTemplate(){
			protected Object operateSession(Session session,Object arg){	
				session.delete(arg);	
				return null;
			}
		}.operateSessionInTransaction(user);
	}					
	//对比参考用
	public void update(User user){
		Session session= HibernateUtil.getSession();	
		Transaction tx = session.beginTransaction();	
		try{
			session.update(user);						
			tx.commit();								
		} catch(Exception e){
			e.printStackTrace();
			tx.rollback();								
		}finally{
		     HibernateUtil. closeSession();				
		}
	}					
}