response返回的不是json

问题

前端ajax请求设置返回类型为json

 $.ajax({
            url:path+"/getData",    //请求的url地址
            dataType:'json',
            beforeSend: function (XMLHttpRequest) {
                XMLHttpRequest.setRequestHeader("token", 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJhdWQiOiIxNTgxMDY2NTQ3OSIsImlhdCI6MTYyODY3OTIyOH0.mhkJrDKM82BdQLf2rqlouRyZMCMGLb9HSJQhDmZRcQk');
            },
            contentType:"application/json;charset=utf-8",
            async:false,//请求是否异步，默认为异步，这也是ajax重要特性
            data:encryRsa,    //参数值
            type:"POST",   //请求方式
            success:function(data){
                //请求成功时处理
                console.log(data);
                var obj = eval('(' + data+ ')');
                console.log(obj);
                if(obj.data != null){
                    console.log(obj.data);
                }
            },

        });

或者vue的axios请求设置返回为json

axios.post('http://127.0.0.1/api/getData', rsaStr,{
            headers: {
              'Content-Type': 'application/json',
              // 'token':'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJhdWQiOiIxNTgxMDY2NTQ3OSIsImlhdCI6MTYyODY2NzkzNH0.U0Zc6nHakGVUZ9eHxkKO9k1MnGhk74BzC5OldZ0oVRQ'
              'token':window.localStorage.getItem('token')
            },
            responseType: 'json'
          }).then((res)=>{
              let obj = eval('(' + res.data+ ')');
              console.log(obj);
            }).catch(function (error) {
              console.log(error);
            });

当后台服务正常是通过注解@Responsebody

在正常情况下，从其它API 返回给前端的结果都是json字符串，前端可以正确解析

但遇到一些异常的情况，返回给前端的结果却是json对象数据，key少了双引号，前端无法正确解析

原因是

@ RestController或者@Responsebody 注解自动将对象转成了json字符串

而 response.getWriter().write() 是直接将json对象写进去，并没有自动转换成json字符串格式

private void responseResult(HttpServletResponse response, Result<?> result) {
        response.setCharacterEncoding("UTF-8");
        response.setHeader("Content-Type", "application/json");
        response.setHeader("Access-Control-Allow-Credentials", "true");
        response.setHeader("Access-Control-Allow-Methods", "GET, POST");
        response.setHeader("Access-Control-Allow-Origin", "*");
        response.setHeader("Access-Control-Max-Age", "3600");
//        response.setHeader("Content-type", "application/json;charset=UTF-8");
        response.setStatus(HttpServletResponse.SC_OK);
        response.setContentType("application/json;charset=UTF-8");
//        ServletOutputStream out = null;
        PrintWriter writer=null;
        try {
            // JSON.toJSONString(result)要获取完整的json字符串，每一个字段都要有set和get方法，不然会缺少某个字段
//            response.getWriter().write(JSON.toJSONString(result));
            writer=response.getWriter();
//            writer.write(result.toString());
            writer.write(JSON.toJSONString(result));
            writer.flush();
        } catch (IOException ex) {
            logger.error(ex.getMessage());
        }finally {
            if(writer!=null) {
                writer.close();
            }
        }
    }

而至于重写的toString()方法为什么没有直接返回json字符串

JSON.toJSONString(resultMap, SerializerFeature.WRITE_MAP_NULL_FEATURES)  返回的字符串中，key 是没有双引