Please help review this PR which disables the unspecified but long-standing feature where an `FtpURLConnection` is opened as a fallback for non-local file URLs.
Before this change, if a file URL has a non-local host component, say `file://remotehost/folder/data.txt`, then the implementation would attempt opening an FTP connection to `remotehost`. After this change, such URLs will be rejected with a `MalformedURLException`, unless the FTP fallback feature is explicitly re-enabled via a system property. This change was initially discussed here: https://mail.openjdk.org/pipermail/net-dev/2025-March/025988.html See the above discussion and CSR draft JDK-8354678 for the motivation for this change. I plan to update the CSR pending an initial round of review of this PR. This PR: * Changes file URL `Handler::openConnection` implementation for unix/windows to throw `MalformedURLException`, unless the FTP fallback feature is explicitly enabled by configuration. * Introduces a new system property `sun.net.www.protocol.file.ftp-enabled` which when set to `true` re-enables the feature. * Updates the existing test `NonLocalFtpFallback` to enable the feature via said system property. * Adds a new test `NonLocalFtpFallbackDisabled` verifying that a `MalformedURLException` is thrown by default for a non-local URL host component. I have added a Release Note as a subtask in the JBS issue, this also needs a review. ------------- Commit messages: - Disable non-local file URLs by default Changes: https://git.openjdk.org/jdk/pull/24657/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24657&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8353440 Stats: 89 lines in 5 files changed: 87 ins; 0 del; 2 mod Patch: https://git.openjdk.org/jdk/pull/24657.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/24657/head:pull/24657 PR: https://git.openjdk.org/jdk/pull/24657
