hibernate学习笔记(六)-----session的管理

       session是hibernate运做的核心，是有SessionFactory所创建，sessionFactory是线程安全的，你可以让多个线程同时存取SessionFactory,而不会有资源共用的问题，然而session不是设计为线程安全的，所以让多个线程共用一个session，将发生资料共用而发生混乱的问题．下面是一个标准类．

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

{

   　 //创建线程局部变量　tLocalsess 

    public static final ThreadLocal tLocalsess = new ThreadLocal();

　　　//创建线程局部变量　tLocaltx

public static final ThreadLocal tLocaltx = new ThreadLocal();

      //取得session

    public static Session currentSession(){

         //从线程变量tLocalsess中，取得当前session

Session session = (Session) tLocalsess.get();

//判断session是否为空，如果为空，将创建一个session,并付给线程变量tLocalsess

    try{

if (session == null){

session = openSession();

tLocalsess.set(session);

}

}catch (HibernateException e){

throw new InfrastructureException(e);

}

return session;

}

//关闭当前session

    public static void closeSession(){

         //从线程变量tLocalsess中，取得当前session

Session session = (Session) tLocalsess.get();

         //设置线程变量tLocalsess为空

tLocalsess.set(null);

try{

            //关闭session

if (session != null && session.isOpen()){

session.close();

}

}catch (HibernateException e){

throw new InfrastructureException(e);

}

}

//事物处理

    public static void beginTransaction(){

      //从线程变量tLocaltx中取得事物管理对象Transaction

        Transaction tx = (Transaction) tLocaltx.get();

try{

            //如果为空就从session中创建一个tx

if (tx == null){

tx = currentSession().beginTransaction();

tLocaltx.set(tx);

}

}catch (HibernateException e){

throw new InfrastructureException(e);

}

}

//提交事物

    public static void commitTransaction(){

      //取得事物

Transaction tx = (Transaction) tLocaltx.get();

try{

            //如果不为空就提交

if (tx != null && !tx.wasCommitted() && !tx.wasRolledBack())

tx.commit();

tLocaltx.set(null);

}catch (HibernateException e){

throw new InfrastructureException(e);

}

}

    //事物回滚    

    public static void rollbackTransaction(){

         //取得tx事物

Transaction tx = (Transaction) tLocaltx.get();

try{

            //将变量清空

tLocaltx.set(null);

if (tx != null && !tx.wasCommitted() && !tx.wasRolledBack()){

                //事物回滚

tx.rollback();

}

}catch (HibernateException e){

throw new InfrastructureException(e);

}

}

   //取得session

private static Session openSession() throws HibernateException{

return getSessionFactory().openSession();

}

   //取得sessionFactory

private static SessionFactory getSessionFactory() throws HibernateException{

return SingletonSessionFactory.getInstance();

}

}

filter的代码：

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();

}

}

}

}