图片上传，需要使用formData 传递部分参数，服务器后台是Jfinal ，但是，我发现似乎取不到前面传递过来的参数，这是为何？到底要怎么取呢？

wx.uploadFile({

url: app.globalData._server +‘erp/wxa/wordRecord/upload’, //仅为示例，非真实的接口地址

filePath: filepath,

name: ‘file’,

formData: { ‘upload_folder’: upload_folder },

success:function(res){

},

fail:function(res){

}

//服务端

[@ActionKey](/user/ActionKey)("/upload")
@Before(WxaReqInterceptor.class)
public void upload() {
    String uploadFolder=getRequest().getParameter('upload_folder');
    //uploadFolder .....取不到数据
}