No bean named 'sessionFactory' is defined

今天在配置openSessionInView时,tomcat启动并没有报错,但是发送请求时却报错,如下:

org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'sessionFactory' is defined
org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanDefinition(DefaultListableBeanFactory.java:387)
org.springframework.beans.factory.support.AbstractBeanFactory.getMergedLocalBeanDefinition(AbstractBeanFactory.java:971)
org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:246)
org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185)
org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:168)
org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:884)
org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.lookupSessionFactory(OpenSessionInViewFilter.java:243)
org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.lookupSessionFactory(OpenSessionInViewFilter.java:227)
org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:171)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)

也不知道怎么的,鬼使神差的我去web.xml配置文件中加了一点配置,问题就解决了,如下:

<init-param>
<param-name>sessionFactoryBeanName</param-name>
<param-value>mysessionfactory</param-value>//sessionFactory的bean的id
</init-param>

为什么会这样我也不知道,还望请教