利用Thread-Specific Storage撰寫一個HibernateUtil

 

HibernateSessionUtil.java

import java.io.Serializable;

import net.sf.hibernate.HibernateException;
import net.sf.hibernate.Session;
import net.sf.hibernate.SessionFactory;
import net.sf.hibernate.Transaction;

public class HibernateSessionUtil implements Serializable
...{
    public static final ThreadLocal tLocalsess = new ThreadLocal();

    public static final ThreadLocal tLocaltx = new ThreadLocal();

    /**//*
     * getting the thread-safe session for using
     */
    public static Session currentSession()...{
        Session session = (Session) tLocalsess.get();

        //open a new one, if none can be found.
        try...{
            if (session == null)...{
                session = openSession();
                tLocalsess.set(session);
            }
        }catch (HibernateException e)...{
            throw new InfrastructureException(e);
        }
        return session;
    }

    /**//*
     * closing the thread-safe session
     */
    public static void closeSession()...{

        Session session = (Session) tLocalsess.get();
        tLocalsess.set(null);
        try...{
            if (session != null && session.isOpen())...{
                session.close();
            }

        }catch (HibernateException e)...{
            throw new InfrastructureException(e);
        }
    }

    /**//*
     * begin the transaction
     */
    public static void beginTransaction()...{
        Transaction tx = (Transaction) tLocaltx.get();
        try...{
            if (tx == null)...{
                tx = currentSession().beginTransaction();
                tLocaltx.set(tx);
            }
        }catch (HibernateException e)...{
            throw new InfrastructureException(e);
        }
    }

    /**//*
     * close the transaction
     */
    public static void commitTransaction()...{
        Transaction tx = (Transaction) tLocaltx.get();
        try...{
            if (tx != null && !tx.wasCommitted() && !tx.wasRolledBack())
                tx.commit();
            tLocaltx.set(null);
        }catch (HibernateException e)...{
            throw new InfrastructureException(e);
        }
    }

    /**//*
     * for rollbacking
     */
    public static void rollbackTransaction()...{
        Transaction tx = (Transaction) tLocaltx.get();
        try...{
            tLocaltx.set(null);
            if (tx != null && !tx.wasCommitted() && !tx.wasRolledBack())...{
                tx.rollback();
            }
        }catch (HibernateException e)...{
            throw new InfrastructureException(e);
        }
    }

    private static Session openSession() throws HibernateException...{
        return getSessionFactory().openSession();
    }

    private static SessionFactory getSessionFactory() throws HibernateException...{
        return SingletonSessionFactory.getInstance();
    }
}


filter中的程式碼如下HibernateSessionCloser.java
public class HibernateSessionCloser implements Filter...{

    protected FilterConfig filterConfig = null;

    public void init(FilterConfig filterConfig)throws ServletException...{
    this.filterConfig = filterConfig;
    }
    
    public void destroy()...{
        this.filterConfig = null;
    }    

    public void doFilter(ServletRequest request, ServletResponse response,
                         FilterChain chain)
    throws IOException, ServletException ...{
        try...{
            chain.doFilter(request, response);
        }
        finally...{
            try...{
                HibernateSessionUtil.commitTransaction();
            }catch (InfrastructureException e)...{
                HibernateSessionUtil.rollbackTransaction();
            }finally...{
                HibernateSessionUtil.closeSession();
            }   
        }

    }
}

然後在操作資料庫之前加上
HibernateSessionUtil.beginTransaction();
HibernateSessionUtil.currentSession();//取得Session