使用RestTemplate发送multipart/form-data格式的数据

public Object sendRequest(Object obj) {
        RestTemplate restTemplate = new RestTemplate();

        //设置请求头
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.MULTIPART_FORM_DATA);

        HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<MultiValueMap<String, String>>(
                popHeaders(obj), headers);
         //发送请求，设置请求返回数据格式为String
        ResponseEntity<String> responseEntity = restTemplate.postForEntity("http:xxx.xx", request, String.class);
                
}
//组装请求体
protected MultiValueMap<String, String> popHeaders(Object obj) {
        SubmitOrderDTO submit = (SubmitOrderDTO) obj;
        MultiValueMap<String, String> map = new LinkedMultiValueMap<String, String>();

        map.add("order_id", submit.getOrderId());
        map.add("userName",submit.getUserName());
        //.....
        return map;
}