IE缓存AJAX请求积极（不仅仅是Firefox，Chrome和Safari）。
有时你需要在请求时设置缓存头控制器。像 cache：false 。我试图像这样修复你的代码

IE caches AJAX requests aggressively (more than Firefox, Chrome, and Safari, anyway). Sometimes you need to set cache header controller when request. Like cache:false. I tried to fix your code like this

request.setCharacterEncoding("utf8");
        //response.setCharacterEncoding("utf8");
        response.setContentType("application/json");
        PrintWriter out = response.getWriter();
        JSONObject jsonObj = (JSONObject) JSONValue.parse(request.getParameter("para"));
        System.out.println(jsonObj.get("message"));
        JSONObject obj = new JSONObject();
        obj.put("message", "hello from server");
        out.print(obj);

我从 application / json更改了你的响应内容类型; charset = utf8 只需 application / json 就行了。