开发一个小程序，需要在小程序上传图片，后台action（struts)保存，前后端代码都写好也调试通过。却遇到个很奇怪的问题。小程序上凡是上传2M（这是经过我反复测试，刚好在这个数值）以上的，后台action可以正常接收并能保存本地。凡是在上传2M以下的，在request里全都获取不到。反复查找了struts里的拦截器，发现正常。前台调用也正常。前后台相关代码如下：

微信小程序：

java代码：

public void upload()throws Exception{

	try {

		Date date = new Date();

		//上传文件

		HttpServletRequest request = ServletActionContext.getRequest();

		HttpServletResponse response = ServletActionContext.getResponse();

		DiskFileItemFactory factory = new DiskFileItemFactory();

		factory.setSizeThreshold(4096); // 设置缓冲区大小，这里是4kb

		String basePath = ServletActionContext.getRequest().getRealPath("/");//获取根目录

		//设置下载目录

		String uploadPath = basePath + "/upload";

		//设置临时目录

		String tempPath = uploadPath +"/temp";

		//uploadPath = uploadPath +"/"+ date.getTime();//添加时间目录防止重复

		this.initDir(uploadPath, tempPath);

		File tempPathFile = new File(tempPath);

        factory.setRepository(tempPathFile);// 设置缓冲区目录

		ServletFileUpload upload = new ServletFileUpload(factory);

		//upload.setSizeMax(34194304); 设置最大文件尺寸，4MB

		List items = upload.parseRequest(request);//得到所有的文件

		Iterator itr = items.iterator();

		String imgUrl;

		while(itr.hasNext()){

			FileItem fileItem = (FileItem) itr.next();

			if(fileItem.isFormField()){

				System.out.println("表单参数名："+fileItem.getFieldName()+",表单参数值："+fileItem.getString("utf-8"));

			}else{

				if(fileItem.getName()!=null && !"".equals(fileItem.getName())){

					System.out.println("上传文件的大小:"+fileItem.getSize());

					System.out.println("上传文件的类型:"+fileItem.getContentType());

					System.out.println("上传文件的名称:"+fileItem.getName());

					//保存文件

					File saveFile = new File(uploadPath,fileItem.getName());

					fileItem.write(saveFile);

					imgUrl = uploadPath+"/"+fileItem.getName();

					System.out.println("上传成功");

				}else{

					System.out.println("没有上传文件");

				}

			}

		}

		Writer out = response.getWriter();

		out.write("success");

		out.flush();

	} catch (Exception e) {

		e.printStackTrace();

		throw new Exception(e);

	}

}

望大家提提意见，看从哪方面着手。