异步返回各种格式工具类

    //发送内容      public static void render(HttpServletResponse response,String contentType,String text){        response.setContentType(contentType);        try {            response.getWriter().write(text);        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }    //发送的是JSON    public static void renderJson(HttpServletResponse response,String text){        render(response, "application/json;charset=UTF-8", text);    }    //发送xml    public static void renderXml(HttpServletResponse response,String text){        render(response, "text/xml;charset=UTF-8", text);    }    //发送text    public static void renderText(HttpServletResponse response,String text){        render(response, "text/plain;charset=UTF-8", text);    }