上传问题　高手帮忙看看　急啊～！！！

以下是出现的异常javax.servlet.ServletException: BeanUtils.populate
org.apache.struts.util.RequestUtils.populate(RequestUtils.java:1254)
org.apache.struts.action.RequestProcessor.processPopulate(RequestProcessor.java:821)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:254)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1482)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:507)
javax.servlet.http.HttpServlet.service(HttpServlet.java:743)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
root cause java.lang.IllegalArgumentException: argument type mismatch
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:324)
org.apache.commons.beanutils.PropertyUtils.setSimpleProperty(PropertyUtils.java:1789)
org.apache.commons.beanutils.PropertyUtils.setNestedProperty(PropertyUtils.java:1684)
org.apache.commons.beanutils.PropertyUtils.setProperty(PropertyUtils.java:1713)
org.apache.commons.beanutils.BeanUtils.setProperty(BeanUtils.java:1019)
org.apache.commons.beanutils.BeanUtils.populate(BeanUtils.java:808)
org.apache.struts.util.RequestUtils.populate(RequestUtils.java:1252)
org.apache.struts.action.RequestProcessor.processPopulate(RequestProcessor.java:821)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:254)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1482)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:507)
javax.servlet.http.HttpServlet.service(HttpServlet.java:743)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)