原因是: web.xml要加上这样一段

  <!-- 配置 ContextLoaderListener 加载 Spring 配置文件 -->
  <!-- needed for ContextLoaderListener -->
  <context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>classpath:spring-persist-*.xml</param-value>
  </context-param>
  <!-- Bootstraps the root web application context before servlet initialization -->
  <listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
  </listener>