扩大作用域的范围我采用的技术是ThreadLocal类来实现

首先需要写一个过滤器

public class OpenSessionInView implements Filter{

  @Override
  public void destroy() {
    // TODO Auto-generated method stub

  }

  @Override
  public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {
    Session session = HibUtil.getSession();//开启session
    chain.doFilter(request, response);//放行
    session.close(); //关闭session
  }

  @Override
  public void init(FilterConfig filterConfig) throws ServletException {
    // TODO Auto-generated method stub

  }

}

在工具类中按如下写

public class HibUtil {
  private static SessionFactory sessionFactory;
  private static final ThreadLocal<Session> sessionThreadLocal = new ThreadLocal<Session>();
  static{
    //获取配置信息 hibernate.cfg.xml
    Configuration configuration = new Configuration().configure();
    //创建一个 ServiceRegistry的实例
    //首先获得其标准建造器,此处用了建造者模式 builder模式来创建对象
    //创建一个标准的构建器
    StandardServiceRegistryBuilder ssb = new StandardServiceRegistryBuilder();
    //建造(得到)ServiceRegistry的实例此处一定要传入//configuration.getProperties()否则会报错UnsupportedOperationException
    ServiceRegistry build = ssb.applySettings(configuration.getProperties()).build();
    //获得session工厂 一个数据库对应一个 SessionFactory
    sessionFactory = configuration.buildSessionFactory(build);
  }
  public static Session getSession(){
    Session session = sessionThreadLocal.get();
    if(session==null||!session.isOpen()){  //这样做的目的是确保每次获取的session是同一个
      sessionThreadLocal.set(sessionFactory.openSession());
    }
    return sessionThreadLocal.get();
  }
}

不要忘了在web.xml中配置

  <filter>
    <filter-name>openSessionInView</filter-name>
    <filter-class>com.chdsxt.filter.OpenSessionInView</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>openSessionInView</filter-name>
    <url-pattern>*.do</url-pattern>
  </filter-mapping>

这样就能确保在service或dao层通过HibUtil.getSession()获取的session是同一个session,这样就达到了扩大作用域范围的要求