The issue here is that `HttpURLConnection` is automatically disconnected (`HttpClient` is set to `null`, `connected` is set to `false`) when a response with no response body bytes is received. This happens before a fake empty body input stream is returned to the user. That behaviour also occurs with any method for which `content-length: 0` is returned (GET, POST, custom, anything), and with any status code (204, 304) for which there is no body.
In this case, the proposed fix is to store the `SSLSession` in the `AbstractDelegateHttpsURLConnection` subclass until such a time where `disconnect()` is explicitely closed. Information pertaining to SSL, such as server certificates, can be extracted from the saved `SSLSession`. ------------- Commit messages: - 8376031: HttpsURLConnection.getServerCertificates() throws "java.lang.IllegalStateException: connection not yet open" for the HEAD method Changes: https://git.openjdk.org/jdk/pull/29489/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29489&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8376031 Stats: 481 lines in 4 files changed: 388 ins; 79 del; 14 mod Patch: https://git.openjdk.org/jdk/pull/29489.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/29489/head:pull/29489 PR: https://git.openjdk.org/jdk/pull/29489
