Frédéric Hannes created IO-821:
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Summary: commons-io 2.15.0 breaks backwards compatibility for
PathUtils.fileContentEquals
Key: IO-821
URL: https://issues.apache.org/jira/browse/IO-821
Project: Commons IO
Issue Type: Bug
Components: Utilities
Affects Versions: 2.15.0
Reporter: Frédéric Hannes
Version {{2.15.0}} of commons-io features performance improvements by
[~ggregory] for PathUtils.fileContextEquals() as listed in the changelog:
_Improve performance of PathUtils.fileContentEquals(Path, Path, LinkOption[],
OpenOption[]) by about 60%, see PathUtilsContentEqualsBenchmark._
The relevant change occurs in [commit
{{dd93554b}}|https://github.com/apache/commons-io/commit/dd93554b692cabe884e7a097e431f475397a3b48#diff-4162512d2bb8d032482958d8dabacc1c2398e95597a49fa5b0fc02aabc8717d6R769],
where the comparison of input streams through {{IOUtils.contentEquals()}} is
replaced with {{RandomAccessFile.contentEquals()}}.
The issue occurs in {{RandomAccessFileMode.create()}}, where
[{{Path.toFile()}}|https://docs.oracle.com/javase/8/docs/api/java/nio/file/Path.html#toFile--]
is called. This method like many in {{Path}}, can throw an
{{UnsupportedOperationException}} if it is not implemented by the filesystem
provider.
In our particular case, we compare files from a zip archive with files on disk
using the [zip filesystem provider that was introduced in Java
7|https://docs.oracle.com/javase/8/docs/technotes/guides/io/fsp/zipfilesystemprovider.html].
The class {{jdk.nio.zipfs.ZipPath}} does not implement {{Path.toFile()}} and
therefore throws an {{UnsupportedOperationException}}.
Though it does not seem unreasonable to limit the functionality of this method
to a specific subset of {{Path}} implementations, this does seem to be a
substantial breaking change in behavior of an existing method, which I am not
sure was intentional.
As a workaround to resolve the issue without downgrading, we now call
{{IOUtils.contentEquals()}} directly.
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