我有一个jsp文件UploadCoupon.jsp如下图片上传
<form:form commandName="uploadcoupon" enctype="multipart/form-data" method="POST">
    <form:input type="file" path="couponImage" class="file_1 required"/><br/>
    <form:errors path="couponImage" cssClass="error" style="color:red" /><br/>
    <input id="uploadCouponButton" type="submit" value="" class="form-submit" />
</form:form> 
Bean 类Coupon.java如下所示
public class Coupon {
    MultipartFile couponImage;
    public MultipartFile getCouponImage() {
        return couponImage;
    }
    public void setCouponImage(MultipartFile couponImage) {
        this.couponImage = couponImage;
    }
}
Dispatcher servlet 具有以下代码
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"/>
控制器UploadCoupon.java如下
public class UploadCoupon extends SimpleFormController
{
    public UploadCoupon()
    {
        setCommandClass(Coupon.class);
        setCommandName("uploadcoupon");
    }
    @Override
    protected ModelAndView onSubmit(HttpServletRequest request,
                                    HttpServletResponse response,
                                    Object command,
                                    BindException errors) throws Exception {
        try {
            Coupon coupon = (Coupon)command;
            MultipartFile multipartFile = coupon.getCouponImage();
            // image type of file processing...
        } catch (Exception e) {
             System.out.println("Exception -"+e.getMessage());
        }
        mv = new ModelAndView(new RedirectView("UploadCoupon.htm");
        return mv;
    }
}
此代码在本地主机上的 Glassfish 服务器上部署时工作正常,但是当我在 Glassfish 服务器上的远程主机上部署它时,multipartFile 对象为 null 并且发生 NullPointerException。我不明白在远程主机上部署它有什么问题?