sessionDao 启动报错

org.springframework.beans.NotWritablePropertyException: Invalid property 'sessionDao' of bean class [org.apache.shiro.web.session.mgt.DefaultWebSessionManager]: Bean property 'sessionDao' is not writable or has an invalid setter method. Did you mean 'sessionDAO'?   我按那个配置sessionDao,启动报错了，谁知道怎么决解