Odd result with canonical paths with intermixed usage of java.io.File and java.nio.file.Files APIs (original) (raw)

Jaikiran Pai jai.forums2013 at gmail.com
Mon Dec 11 15:46:06 UTC 2017


Moved this thread from discussions mailing list[1] to here. Comments inline.

On 11/12/17 7:55 PM, Alan Bateman wrote:

On 11/12/2017 14:06, Jaikiran Pai wrote:

:

So a few related questions that I have are: 1. Is this inconsistency an expected behaviour or is this a bug? 2. If this is an expected behaviour, then would it be a better idea (as an application developer) to use Path.toRealPath[2] instead of using the File.getCanonicalPath()? Are these 2 APIs semantically equivalent? The File.getCanonicalPath() talks about the canonical path being "unique" paths but the Path.toRealPath has no such mentions. The correctness issues with the canonicalization cache is a long standing issue [1]. You can workaround it by running with -Dsun.io.useCanonCaches=false as I think you have found. The goal is to eventually disable and remove it. The first steps to get there happened in JDK 9 when FilePermission was changed to not canonicalize by default (FilePermission was the original motivation for this cache). If you have follow-up questions then please bring the thread to core-libs-dev. -Alan [1] https://bugs.openjdk.java.net/browse/JDK-7066948 Thanks Alan. Given that the cache itself is being planned to be eventually removed, that answers the main part of my question and I can workaround this issue in a couple of ways (disabling the cache using that system property is one way) in the application, till that time.

The only remaining part that I'm curious about is this:

... would it be a better idea (as an application developer) to use Path.toRealPath[2] instead of using the File.getCanonicalPath()? Are these 2 APIs semantically equivalent? The File.getCanonicalPath() talks about the canonical path being "unique" paths but the Path.toRealPath has no such mentions.

[1] http://mail.openjdk.java.net/pipermail/discuss/2017-December/004655.html

-Jaikiran



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