RFR: 8353440: Disable FTP fallback for non-local file URLs by default [v6]

[Eirik Bjørsnøs]

On Thu, 24 Apr 2025 10:08:10 GMT, Daniel Fuchs <dfuchs at openjdk.org> wrote:

> You will still need to update `java/net/URL/OpenStream.java` to make it pass with the new changes. Possibly have two `@run`, one with `-Djdk.net.file.ftpfallback=true` and one without and adapt the test expectation based on the presence (and value) of the property.

Hmm yes..

However, I find it somewhat dubious that 8202708 is crammed into this test which originally was written to test the non-proxy aspect in 4064962. Using that test to also verify that a non-existing `file://` UNC path leads to an FtpURLConnection which then fails with an `UnknownHostException` seems a bit convoluted and a mixing of concerns.

I think I would feel better if this aspect was instead verified in a new test added to the recently introduced `NonLocalFtpFallback`:


/**
 * Verify that opening a stream on a non-proxy URLConnection for a non-local
 * file URL which is not an existing UNC path fails with UnknownHostException
 * when the fallback FtpURLConnection attempts to connect to the non-existing
 * FTP server.
 *
 * See bug 8202708
 */
public void verifyFtpConnectionException() throws IOException {
    URL url  = new URL("file://h7qbp368oix47/not-exist.txt");
    assertThrows(UnknownHostException.class, () -> {
        InputStream in = url.openConnection(Proxy.NO_PROXY).getInputStream();
    });
}


We could then remove any FTP aspect from `OpenStream.java` by reverting 8202708 and keep any FTP fallback testing in the recently introduced tests (disable and not disabled). This seems cleaner to me and also reduces duplicated / redundant testing.

Any thoughts?

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PR Comment: https://git.openjdk.org/jdk/pull/24657#issuecomment-2827164702