HttpURLConnection抛出响应代码400的json Java读帖子

Question

我正在打开一个HttpURLConnection，并使用POST方法发送一个JSON请求，从另一个类构建。JSON的结构是正确的，因为我已经在调试时对它进行了验证。尝试读取服务器给出的输出响应时引发异常。这是给出的错误

java.io.IOException: Server returned HTTP response code: 400 for URL:

但是，当我使用chrome扩展名POST方法从web浏览器手动输入Url时。我可以查看响应，一切正常。因此，我确信这与我建立连接和读/写的以下代码有关

    URL obj = new URL(url);

    HttpURLConnection connection = (HttpURLConnection) obj.openConnection();
    //add request header
    connection.setRequestMethod("POST");
    connection.setRequestProperty("Content-Type", "application/json");
    //mapping objects to json
    BatchRequest requestParameters = new BatchRequest(o,d);

    ObjectMapper mapper = new ObjectMapper();

    String json = mapper.writeValueAsString(requestParameters);

    connection.setDoOutput(true);
    DataOutputStream os = new DataOutputStream(connection.getOutputStream());

    os.writeBytes(json);
    os.flush();
    os.close();
         // this is where the program throws the exception  
    BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));

    String inputLine;
    StringBuilder response = new StringBuilder();

    while ((inputLine = in.readLine()) != null) {
            response.append(inputLine);
    }
    in.close();

URL和JSON请求都是正确的，因为当我在浏览器上尝试手动连接时，它们可以工作

Answer 1

不需要DataOutputStream。只是：

OutputStream os = con.getOutputStream();