页面上做成普通的file文件上传，后台怎么处理才能拿到文件里的数据（实体类已经写好了）
$.ajaxFileUpload({
url:"${base}/yun/configure/yungateway/importJson",
type:'POST',
secureuri : false,
fileElementId : 'jsonFile',
dataType : 'JSON',
success : function (data, status){
@At
@Ok("json")
@AdaptBy(type = JsonAdaptor.class)
public Object importJson(@Param("importJson")File file){
这里直接报错
}
[WARN ] 2017-09-21 15:04:31,626 org.nutz.mvc.impl.processor.FailProcessor.process(FailProcessor.java:28) - Error@/yun/configure/yungateway/importJson :
java.lang.NullPointerException
at org.nutz.lang.Streams._input(Streams.java:673)
at org.nutz.lang.Streams.fileIn(Streams.java:506)
at org.nutz.lang.Streams.fileInr(Streams.java:538)
at org.nutz.json.Json.fromJsonFile(Json.java:123)
at com.znzz.app.web.modules.controllers.platform.instruments.InsYunGatewayController.importJson(InsYunGatewayController.java:224)
at com.znzz.app.web.modules.controllers.platform.instruments.InsYunGatewayController$FM$importJson$526d83ae20d2dd1206e3c2efe51878d3.invoke(InsYunGatewayController.java)