struts映射文件出错

严重: Servlet.service() for servlet jsp threw exception
javax.servlet.jsp.JspException: Cannot retrieve definition for form bean userForm

查看映射文件struts-config.xml
<struts-config>
  <data-sources />
  <form-beans>
    <form-bean name="UserForm" type="com.jspdev.ch17.UserForm"></form-bean>
  </form-beans>
  <global-exceptions />
  <global-forwards>
  <forward name="userCreated" path="/viewUser.jsp"></forward>
  </global-forwards>
<action-mappings>
  <action path="/createUser"
  type="com.jspdev.ch17.UserAction"
  name="userForm"
  scope="request"
  validate="true"
  input="/createUser.jsp"></action>
  </action-mappings>
  <message-resources parameter="ApplicationResources" />
</struts-config>

注意:<form-bean name="UserForm" type="com.jspdev.ch17.UserForm"></form-bean>
与 <action path="/createUser"
  type="com.jspdev.ch17.UserAction"
  name="userForm"
  scope="request 
这两个name的值必须相等
UserForm    userForm注意区分大小写