package com.tarena.shoppingcart.util;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {
	private static SessionFactory sf;
	private static ThreadLocal<Session> sessions = new ThreadLocal<Session>();
	private static ThreadLocal<Transaction> transactions = new ThreadLocal<Transaction>();
    
    static
    {
        try
        {
            Configuration config = new Configuration();
            sf = config.configure().buildSessionFactory();
        }catch(Throwable t)
        {
            t.printStackTrace();
            throw new ExceptionInInitializerError(t);
        }
    }
    
    //取得當前線程的session實例
    public static Session currentSession(){
    	Session s = sessions.get();
    	//如果當前session實例存在并可用，則返回
		if(s!=null && s.isOpen()){
			return s;
		}
		
		//如果當前session不存在或不可用，則創建一個新的session實例，保存并返回
		sessions.set(sf.openSession());
		return sessions.get();
    }
    
    //關閉當前線程的session
    public static void closeSession(){
    	Session s = (Session) sessions.get();
		if(s!=null && s.isOpen()){
			s.close();
		}
		//解除引用
		sessions.set(null);
    }
    
    //開始一個事務
    public static void beginTransaction(){
    	//如果當前線程沒有開啟的事務則開始一個新的事務，并保存該事務
    	if(transactions.get()==null){
    		transactions.set(currentSession().beginTransaction());
    	}
    }
    
    //提交當前事務
    public static void commitTransaction(){
    	Transaction tran = transactions.get();
    	//提交當前事務并解除保存的引用
		if(tran!=null && !tran.wasCommitted() && !tran.wasRolledBack()){
			tran.commit();
			transactions.set(null);
		}
	}
	
    //回滾當前事務
	public static void roolbackTransaction(){
		Transaction tran = transactions.get();
    	//回滾當前事務并解除保存的引用
		if(tran!=null && !tran.wasCommitted() && !tran.wasRolledBack()){
			tran.rollback();
			transactions.set(null);
		}
	}
}