Java RestTemplate.exchange返回400空异常

Question

尝试使用org.springframework.web.client.RestTemplate类进行POST调用时出现以下错误：

"400 null","stackTrace":"org.springframework.web.client.HttpClientErrorException: 400 null

下面是我的代码：

public void PostInsertOrUpdateDisplayCounts(CountsDataResults countsDataResults, String displayId) {

        String postUrl = "http://zld05300.vci.com:38767/application/display/C9B367BE340288EFE7D835FD587F2A3/counts";

        RestTemplate restTemplate = new RestTemplate();
        HttpHeaders headers = new HttpHeaders();

        headers.setContentType(MediaType.APPLICATION_JSON);

        HttpEntity<CountsDataResults> countsDataResultsEntity = new HttpEntity<CountsDataResults>(countsDataResults, headers);

        //execute the post call:
        ResponseEntity<Response> reponseEntity  = restTemplate.exchange(postUrl, HttpMethod.POST, countsDataResultsEntity, Response.class);

    }

以下是将接收请求的服务器代码：

@POST
    @Path("/application/display/{displayId}/counts")
    @Consumes(MediaType.APPLICATION_JSON)
    @Produces(MediaType.APPLICATION_JSON)
    public Response insertOrUpdateDisplayCounts(@RequestBody CountsDataResults countsList,@PathParam("displayId")String displayId);

下面是insertOrUpdateDisplayCounts方法的实现：

@Override
    public Response insertOrUpdateDisplayCounts(CountsDataResults countsList, String displayId) {
        String result = countsAPI.insertOrUpdateDisplayCountTables(countsList, displayId);
        if(result == "success")
            return Response.created(null).build();
        else
            return Response.status(Status.FORBIDDEN).build();
    }

我很肯定参数参数为非null，并且我已经成功地使用邮递员对端点进行了相同的POST调用测试，并收到了期望的响应-为什么我会收到此异常？