Reddit api Oauth：服务器返回HTTP响应代码：411，URL错误

Question

我正在尝试从https://www.reddit.com/api/v1/access_token获取访问令牌。为此，我需要向上述URL发送一个CLIENT_ID和一个CLIENT_SECRET。我是使用邮递员这样做的：

如屏幕快照中突出显示的那样，我已经发送了一个grant_type作为一个GET参数，值是client_credentials和一个Authorization参数，值是Basic heregoestheencodedkeyandid。请求类型设置为POST。它正常工作-我在JSON响应中得到了一个访问令牌。

但是，当我尝试通过Java来做同样的事情时，我收到了Server returned HTTP response code: 411错误：

public class RedditExample {
        private static String loginLink = "https://www.reddit.com/api/v1/access_token";

 public static void main(String[] args)  {
                RedditExample redditExample = new RedditExample ();

                redditExample.login();
        }

public boolean login()  {
            try  {
                URL loginURL = new URL(loginLink + "?grant_type=client_credentials");
                HttpURLConnection connection = (HttpURLConnection) loginURL.openConnection();
                setupPOSTConnection(connection);

                InputStream input = connection.getInputStream();
                String inputString = new Scanner(input, "UTF-8").useDelimiter("\\Z").next();

                System.out.println(inputString);
            }

            catch (Exception e) {
                System.out.println(e.toString());
            }

            return true;
        }

private static void setupPOSTConnection(HttpURLConnection connection) throws Exception  {
            connection.setDoOutput(true);
            connection.setRequestMethod("POST");

            connection.setRequestProperty("Authorization", "Basic heregoestheencodedkeyandid");
            connection.connect();
        }
}

与Postman相比，我不确定我在这里所做的不同，所以我们将不胜感激。

编辑：这是我尝试添加的内容：

connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

connection.setDoInput(true); connection.setDoOutput(true); connection.setRequestProperty("Content-Length", "0"); connection.setRequestProperty("Content-Length", "10");

String userAgent = "test /u/someuser";
connection.setRequestProperty("User-Agent", userAgent);

不幸的是，这两个都不起作用-错误仍然相同。

Answer 1

HttpUrlConnection不采用显式设置content-length的方法。因此，只需提供没有内容的请求正文即可。

StringBuilder postDataBuilder = new StringBuilder();
        byte[] postData = postDataBuilder.toString().getBytes("UTF-8");

        OutputStream out = conn.getOutputStream();
        out.write(postData);
        out.close();

所以方法将是这样的：-

private static void setupPOSTConnection(HttpURLConnection connection) throws Exception  {
            connection.setDoOutput(true);
            connection.setRequestMethod("POST");

            connection.setRequestProperty("Authorization", "Basic heregoestheencodedkeyandid");
StringBuilder postDataBuilder = new StringBuilder();
        byte[] postData = postDataBuilder.toString().getBytes("UTF-8");

        OutputStream out = conn.getOutputStream();
        out.write(postData);
        out.close();
            connection.connect();
        }

我还发现了另一种简单添加一行的方法：-

private static void setupPOSTConnection(HttpURLConnection connection) throws Exception  {
                connection.setDoOutput(true);
                connection.setRequestMethod("POST");

                connection.setRequestProperty("Authorization", "Basic heregoestheencodedkeyandid");
    conn.setFixedLengthStreamingMode(0);
                connection.connect();
            }

Answer 2

当服务器出于任何原因拒绝接受不带内容长度标头的消息时，

HTTP状态代码411（必需的长度）由服务器发送作为响应。 如果没有Content-Length标头，则服务器可能会接受或可能不会接受内容，并且此API似乎很挑剔。请参阅this post，详细介绍使用Java进行有效的POST连接。