struts错误 Cannot retrieve mapping for action /preorder 请帮忙解决？

如上，
相关代码：
pre_order.jsp:
<html:form action="/preorder">（试过将/preorder改成preorder.do;/preorder.do，但均无果）
………………
</html:form>struts-config.xml:
<form-beans>
<form-bean name="preorderForm" type="com.products.struts.form.PreorderForm" />
</form-beans>        <action-mappings>
       <action attribute="preorderForm" input="/pre_order.jsp" name="preorderForm"
path="/preorder" scope="request" type="com.products.struts.action.PreorderAction">
      <set-property property="cancellable" value="true" />
      <forward name="order" path="/order.jsp" />
      </action>
</action-mappings>数据库连接没有问题，当进入pre_order.jsp界面时，显示问题如下：HTTP Status 500 -
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:553)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:442)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:389)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:333)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
root causejavax.servlet.ServletException: javax.servlet.jsp.JspException: Cannot retrieve mapping for action /preorder
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:911)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:840)
org.apache.jsp.pre_005forder_jsp._jspService(pre_005forder_jsp.java:120)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:389)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:333)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
root causejavax.servlet.jsp.JspException: Cannot retrieve mapping for action /preorder
org.apache.struts.taglib.html.FormTag.lookup(FormTag.java:759)
org.apache.struts.taglib.html.FormTag.doStartTag(FormTag.java:443)
org.apache.jsp.pre_005forder_jsp._jspx_meth_html_005fform_005f0(pre_005forder_jsp.java:137)
org.apache.jsp.pre_005forder_jsp._jspService(pre_005forder_jsp.java:87)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:389)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:333)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)为什么会这样呢？我应该如何改正才能让它正常运行？