HttpURLConnection 在 POST 上失败，HTTP 400

Question

HttpURLConnection 有时对http URL 的 POST 操作会失败。在我的情况下，以下失败了大约一百次：

byte[] formData = ("mgnlUserId=" + user + "&mgnlUserPSWD=" + user).getBytes(StandardCharsets.UTF_8);
URL url = new URL("http://localhost:8080/magnoliaAuthor/.magnolia/admincentral");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setDoOutput(true);
connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
connection.setRequestMethod("POST");
connection.setRequestProperty("charset", "utf-8");
connection.setRequestProperty("Content-Length", Integer.toString(formData.length));
connection.getOutputStream().write(formData);
connection.connect();

// Sometimes fails with response code being 400
assertEquals(200, connection.getResponseCode());

服务器也抱怨错误的请求：

HTTP Status 400 – Bad Request
Invalid character found in method name [User-Agent:]. HTTP method names must be tokens
The server cannot or will not process the request due to something that is perceived to be a client error (e.g., malformed request syntax, invalid request message framing, or deceptive request routing).
java.lang.IllegalArgumentException: Invalid character found in method name [User-Agent:]. HTTP method names must be tokens

这里有一些 example code 用于重现问题。

目前这对我来说似乎是一个错误，但我在 Java 错误跟踪器中找不到任何相关内容。

任何人遇到类似问题并有解决方法？

Answer 1

这确实是HttpURLConnection的bug。

查看通过网络传输的 HTTP 请求，我可以看到 HTTP 方法设置为 User-Agent: 而不是 GET：

并且日志输出显示正在发送相同的错误请求：

Nov 03, 2021 8:37:01 PM sun.net.www.protocol.http.HttpURLConnection plainConnect0
FINEST: ProxySelector Request for http://localhost:8080/magnoliaAuthor/.magnolia/admincentral
Nov 03, 2021 8:37:01 PM sun.net.www.http.HttpClient logFinest
FINEST: KeepAlive stream retrieved from the cache, sun.net.www.http.HttpClient(http://localhost:8080/magnoliaAuthor/.magnolia/admincentral;jsessionid=44DEE0C8C535782A6B4932E9F0D455ED)
Nov 03, 2021 8:37:01 PM sun.net.www.protocol.http.HttpURLConnection plainConnect0
FINEST: Proxy used: DIRECT
Nov 03, 2021 8:37:01 PM sun.net.www.protocol.http.HttpURLConnection writeRequests
FINE: sun.net.www.MessageHeader@15b170d89 pairs: {POST /magnoliaAuthor/.magnolia/admincentral HTTP/1.1: null}{Content-Type: application/x-www-form-urlencoded}{Cookie: csrf=ZOxgq4P_WMgLjCm3J4mWPEFFNhmIUiHlq9of5JhtKys}{charset: utf-8}{User-Agent: Java/1.8.0_181}{Host: localhost:8080}{Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2}{Connection: keep-alive}{Content-Length: 92}
Nov 03, 2021 8:37:01 PM sun.net.www.protocol.http.HttpURLConnection writeRequests
FINE: sun.net.www.MessageHeader@15b170d89 pairs: {POST /magnoliaAuthor/.magnolia/admincentral HTTP/1.1: null}{Content-Type: application/x-www-form-urlencoded}{Cookie: csrf=ZOxgq4P_WMgLjCm3J4mWPEFFNhmIUiHlq9of5JhtKys}{charset: utf-8}{User-Agent: Java/1.8.0_181}{Host: localhost:8080}{Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2}{Connection: keep-alive}{Content-Length: 92}
Nov 03, 2021 8:37:01 PM sun.net.www.protocol.http.HttpURLConnection getInputStream0
FINE: sun.net.www.MessageHeader@52ae5ad55 pairs: {null: HTTP/1.1 302}{Set-Cookie: JSESSIONID=88DCCC46C9E70CBA8262CF8060A033C0; Path=/magnoliaAuthor; HttpOnly}{Location: /magnoliaAuthor/.magnolia/admincentral;jsessionid=88DCCC46C9E70CBA8262CF8060A033C0}{Content-Length: 0}{Date: Wed, 03 Nov 2021 19:37:01 GMT}
Nov 03, 2021 8:37:01 PM sun.net.www.protocol.http.HttpURLConnection followRedirect0
FINE: Redirected from http://localhost:8080/magnoliaAuthor/.magnolia/admincentral to http://localhost:8080/magnoliaAuthor/.magnolia/admincentral;jsessionid=88DCCC46C9E70CBA8262CF8060A033C0
Nov 03, 2021 8:37:01 PM sun.net.www.protocol.http.HttpURLConnection plainConnect0
FINEST: ProxySelector Request for http://localhost:8080/magnoliaAuthor/.magnolia/admincentral;jsessionid=88DCCC46C9E70CBA8262CF8060A033C0
Nov 03, 2021 8:37:01 PM sun.net.www.protocol.http.HttpURLConnection plainConnect0
FINEST: Proxy used: DIRECT
Nov 03, 2021 8:37:01 PM sun.net.www.protocol.http.HttpURLConnection writeRequests
FINE: sun.net.www.MessageHeader@774fca3c4 pairs: {User-Agent: Java/1.8.0_181}{Host: localhost:8080}{Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2}{Connection: close}
Nov 03, 2021 8:37:01 PM sun.net.www.protocol.http.HttpURLConnection getInputStream0
FINE: sun.net.www.MessageHeader@57256a0d6 pairs: {null: HTTP/1.1 400}{Content-Type: text/html;charset=utf-8}{Content-Language: en}{Content-Length: 2244}{Date: Wed, 03 Nov 2021 19:37:01 GMT}{Connection: close}

深入挖掘我发现，当HttpURLConnection 在重用连接上启动POST 但发现套接字已关闭时，它将在内部recover 并打开一个新连接。如果此 POST 成功并且服务器发送重定向状态 (302)，它将尝试遵循重定向。但是，在内部，它无法正确初始化请求标头：在creating a new set of headers 之后，它将使用not set the HTTP 方法，因为此时failedOnce 在关闭套接字上的第一个POST 时为真

更新：现在是tracked as a bug。