java - HttpURL连接 : Already connected after redirect

Question

我需要连接到一个 Web 应用程序，如果请求的 URL 未在应用程序内映射，该应用程序将执行 HTTP 重定向。 (例如:/users ->/users/)对于身份验证，我们使用基于 token 的方法，因此我必须在每个请求中发送一个 token 。

当我在重定向后设置 token 时，我总是收到 java.lang.IllegalStateException: Already connect 。有人可以帮我解决这个问题吗？

这是我所做的:

try {
      // setup connection
      URL url = new URL(ENDPOINT + path);
      HttpURLConnection connection = (HttpURLConnection) url.openConnection();
      connection.setRequestMethod(method.toString().toUpperCase());
      connection.setInstanceFollowRedirects(false);

      // has the request been redirected?
      if (connection.getResponseCode() == HttpURLConnection.HTTP_MOVED_PERM) {
        String newUrl = connection.getHeaderField("Location");
        connection = (HttpURLConnection) new URL(ENDPOINT + newUrl).openConnection();
      }

      if (useToken) {
        connection.addRequestProperty("Authorization", testToken);
      }

      // post data
      if (data != null) {
        connection.setDoOutput(true);
        connection.addRequestProperty("Content-Type", "application/json");
        String json = new Gson().toJson(data);
        try (OutputStream dataStream = connection.getOutputStream()) {
          dataStream.write(json.getBytes());
        }
      }


      // retrieve response
      String body = IOUtils.toString(connection.getInputStream());
      return new TestResponse(connection.getResponseCode(), body);
    } catch (IOException ex) {
      LOGGER.error(ex.getMessage());
      return null;
    }

Answer 1

我认为您应该设置connection.setInstanceFollowRedirects(true)，这将使连接遵循 HTTP 重定向，然后删除

// has the request been redirected?
      if (connection.getResponseCode() == HttpURLConnection.HTTP_MOVED_PERM) {
        String newUrl = connection.getHeaderField("Location");
        connection = (HttpURLConnection) new URL(ENDPOINT + newUrl).openConnection();

从您的代码中我看不出为什么需要将 setInstanceFollowRedirects 设置为 false