<!--转换json数据-->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.58</version>
        </dependency>

 List<Map> users = userServiceImpl.queryAllUser();
        //以json数据的形式输出
        JSONObject object=new JSONObject();
        object.put("users", users);
        response.setContentType("text/html;charset=UTF-8");
        try {
            response.getWriter().write(object.toString());
        } catch (IOException e) {
            e.printStackTrace();
        }