使用 JSON 对象作为负载向 REST API 发出 POST 请求

我正在尝试使用具有 JSON 负载的 POST 请求从 REST API 获取 JSON 响应（应在发送前转换为 URL 编码文本）。我已经按照一些教程来实现该过程，但收到状态代码 400 的错误。我可能没有对给定的 JSON 字符串进行编码或丢失了某些内容。请帮我解决这个问题。谢谢。

这是我的代码

    try {
        URL url = new URL("https://appem.totango.com/api/v1/search/accounts/health_dist");
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setDoOutput(true);
        conn.setRequestMethod("POST");
        conn.setRequestProperty("Content-Type", "application/json");
        conn.setRequestProperty("app-token", "1a1c626e8cdca0a80ae61b73ee0a1909941ab3d7mobile+testme@totango.com");
        conn.setRequestProperty("Accept", "application/json, text/javascript, */*; q=0.01");
        conn.setRequestProperty("X-Requested-With","XMLHttpRequest");

        String payload = "{\"terms\":[{\"type\":\"totango_user_scope\",\"is_one_of\":[\"[email protected]\"]}],\"group_fields\":[{\"type\":\"health\"}]}";

        OutputStream os = conn.getOutputStream();
        os.write(payload.getBytes());
        os.flush();

        if (conn.getResponseCode() != HttpURLConnection.HTTP_CREATED) {
            throw new RuntimeException("Failed : HTTP error code : "
                    + conn.getResponseCode());
        }

        BufferedReader br = new BufferedReader(new InputStreamReader(
                (conn.getInputStream())));

        String output;
        System.out.println("Output from Server .... \n");
        while ((output = br.readLine()) != null) {
            System.out.println(output);
        }
        conn.disconnect();
    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

在关注许多帖子和教程超过 24 小时后，我发现我没有正确发送 URL 参数。我还了解到 REST API 调用使用ApacheHttp客户端相对来说比较容易。我解决了 HTTP 错误代码 400 并从服务器获取了响应。这是我的问题的工作代码。

        try {
            httpClient = HttpClients.createDefault();
            httpPost = new HttpPost("https://appem.totango.com/api/v1/search/accounts/health_dist");

            List<NameValuePair> headers = new ArrayList<NameValuePair>(); //ArrayList to store header parameters
            List<NameValuePair> urlParameters = new ArrayList<NameValuePair>(); //ArrayList to store URL parameters

            urlParameters.add(new BasicNameValuePair("query","{\"terms\":[{\"type\":\"totango_user_scope\",\"is_one_of\":[\"[email protected]\"]}],\"group_fields\":[{\"type\":\"health\"}]}"));
            headers.add(new BasicNameValuePair("app-token", "1a1c626e8cdca0a80ae61b73ee0a1909941ab3d7mobile+testme@totango.com"));
            headers.add(new BasicNameValuePair("Accept", "application/json, text/javascript, */*; q=0.01"));
            headers.add(new BasicNameValuePair("X-Requested-With", "XMLHttpRequest"));
            httpPost.setEntity(new UrlEncodedFormEntity(urlParameters));

            for (NameValuePair h : headers)
            {
                httpPost.addHeader(h.getName(), h.getValue());
            }

            response = httpClient.execute(httpPost);

            if (response.getStatusLine().getStatusCode() != 200) {
                throw new RuntimeException("Failed : HTTP error code : "
                        + response.getStatusLine().getStatusCode());
            }

            BufferedReader br = new BufferedReader(new InputStreamReader(
                    (response.getEntity().getContent())));

            String output;
            System.out.println("Output from Server .... \n");
            while ((output = br.readLine()) != null) {
                System.out.println(output);
            }
        } catch (MalformedURLException e) {

            e.printStackTrace();

        } catch (IOException e) {

            e.printStackTrace();

        } finally {
            try{
                response.close();
                httpClient.close();
            }catch(Exception ex) {
                ex.printStackTrace();
            }
        }