how to rebuild hibernate sessionFactory?

http://forum.springframework.org/showthread.php?t=48214&highlight=LocalSessionFactoryBean
I modify hibernate mapping file to add some columns for dynamic-component at runtime,I need it take effect at runtime.

way 1,don't rebuild sessionFactory and use the original sessionFactory:
1.get entity's PersistentClass use ctx.getBean("&sessionFactory").getConfiguration(). getClassMapping(entityClassName)
and modify it
2.call ctx.getBean("&sessionFactory").updateDatabaseSchem a();

but it doesn't works at all,it doesn't update database schema,and generated sql doesn't include those columns.
anything else I need to do with sessionFactory or configuration?

way 2,rebuild sessionFactory using a sessionFactory proxy:
1.set hibernate properties use hibernate.hbm2ddl.auto=update
2.change original sessionFactory's id to '_sessionFactory',and add two beans.

<bean id="sessionFactory" 
        class="org.springframework.aop.framework.ProxyFactoryBean"> 
        <property name="targetSource" 
            ref="refreshableSessionFactoryTargetSource" /> 
</bean> 
<bean id="refreshableSessionFactoryTargetSource" class="RefreshableSessionFactoryTargetSource" /> 

<bean id="_sessionFactory" 
        class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"> 
        <property name="mappingLocations"> 
            <list> 
                <value> 
                    classpath*:resources/hibernate/**/*.hbm.xml 
                </value> 
            </list> 
        </property> 
</bean> 

import java.lang.reflect.Method; 

import org.hibernate.SessionFactory; 
import org.springframework.aop.target.dynamic.AbstractRefreshableTargetSource; 
import org.springframework.beans.factory.InitializingBean; 
import org.springframework.beans.factory.annotation.Autowired; 
import org.springframework.context.ApplicationContext; 
import org.springframework.orm.hibernate3.LocalSessionFactoryBean; 

public class RefreshableSessionFactoryTargetSource extends 
        AbstractRefreshableTargetSource implements InitializingBean { 

    @Autowired 
    private ApplicationContext ctx; 

    private LocalSessionFactoryBean lsfb; 

    private SessionFactory target; 

    private boolean needRefresh = false; 

    public void afterPropertiesSet() throws Exception { 
        lsfb = (LocalSessionFactoryBean) ctx.getBean("&_sessionFactory"); 
        target = (SessionFactory) lsfb.getObject(); 
    } 

    protected synchronized Object freshTarget() { 
        if (!needRefresh) { 
            needRefresh = true; 
            return target; 
        } 
        target.close(); 
        target = null; 
        try { 
            Method method = LocalSessionFactoryBean.class 
                    .getDeclaredMethod("buildSessionFactory"); 
            method.setAccessible(true); 
            target = (SessionFactory) method.invoke(lsfb); 
            return target; 
        } catch (Exception e) { 
            throw new RuntimeException(e); 
        } 
    } 

    public SessionFactory getSessionFactory() { 
        return target; 
    } 

} 

3.call ctx.getBean("refreshableSessionFactoryTargetSource ").refresh();

it works fine,but got a exception when execute a hibernate query

Caused by: org.hibernate.HibernateException: No Hibernate Session bound to thread, and configuration does not allow creation

of non-transactional one here
at org.springframework.orm.hibernate3.SpringSessionCo ntext.currentSession(SpringSessionContext.java:63)
at org.hibernate.impl.SessionFactoryImpl.getCurrentSe ssion(SessionFactoryImpl.java:544)
at sun.reflect.GeneratedMethodAccessor77.invoke(Unkno wn Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(De legatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.springframework.aop.support.AopUtils.invokeJoi npointUsingReflection(AopUtils.java:301)
at org.springframework.aop.framework.JdkDynamicAopPro xy.invoke(JdkDynamicAopProxy.java:198)
at $Proxy11.getCurrentSession(Unknown Source)

I'am not using HibernateDaoSupport and use sessionFactory.getCurrentSession() directly in my Dao
it will execute SessionFactoryUtils.doGetSession(this.sessionFacto ry, false) in

org.springframework.orm.hibernate3.SpringSessionCo ntext,but if I switch to original sessionFactory,it wouldn't execute

SessionFactoryUtils.doGetSession(this.sessionFacto ry, false)
is this difference caused by sessionFactory is a proxy?how can I resolve this problem?