刚刚看见好像有相同的问题，但是我试了一下并没有解决。
就是这个方法里边的log：

 @AdaptBy(type=UploadAdaptor.class, args={"${app.root}/WEB-INF/tmp/user_avatar", "8192", "utf-8", "20000", "102400"})
    @POST
    @Ok(">>:/user/profile")
    @At("/avatar")
    public void uploadAvatar(@Param("file")TempFile tf,
                             @Attr(scope=Scope.SESSION, value="me")int userId,
                             AdaptorErrorContext err) {
        String msg = null;
        if (err != null && err.getAdaptorErr() != null) {
            msg = "文件大小不符合规定";
        } else if (tf == null) {
            msg = "空文件";
        } else {
            UserProfile profile = get(userId);
            try {
                BufferedImage image = Images.read(tf.getFile());
                image = Images.zoomScale(image, 128, 128, Color.WHITE);
                ByteArrayOutputStream out = new ByteArrayOutputStream();
                Images.writeJpeg(image, out, 0.8f);
                profile.setAvatar(out.toByteArray());
                dao.update(profile, "^avatar$");
            } catch(DaoException e) {
                log.info("System Error", e);
                msg = "系统错误";
            } catch (Throwable e) {
                msg = "图片格式错误"; }
        }

        if (msg != null)
            Mvcs.getHttpSession().setAttribute("upload-error-msg", msg);
    }
}