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https://issues.apache.org/jira/browse/VFS-683?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16695425#comment-16695425
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Daryl Odnert commented on VFS-683:
----------------------------------
Here is a Java program that demonstrates a problem where if you have more than
one thread attempting to read the contents of the children of the same archive
file, you will get exceptions thrown. The exceptions this applications receives
from VFS are not identical to the {{NullPointerException}} that is listed in
the original problem description, but I think this does demonstrate that there
is either a thread-safety issue that needs to be fixed, or some documentation
that needs to be clarified.
[^Main.java]
> Thread safety issue in VFSClassLoader - NullPointerException thrown
> -------------------------------------------------------------------
>
> Key: VFS-683
> URL: https://issues.apache.org/jira/browse/VFS-683
> Project: Commons VFS
> Issue Type: Bug
> Affects Versions: 2.2
> Reporter: Daryl Odnert
> Priority: Major
> Attachments: Main.java
>
>
> In my application, I have two instances of the {{VFSClassLoader}}, each of
> which is being used in a distinct thread. Both {{VFSClassLoader}} instances
> refer to the same compressed file resource described by a {{FileObject}} that
> is passed to the class loader's constructor. Intermittently, the application
> throws an exception with the stack trace shown below. So, there seems to be
> either a race condition in the code or an undocumented assumption here. If it
> is unsupported for two {{VFSClassLoader}} instances to refer to the same
> resource (file), then that assumption should be documented. But if that is
> not the case, then there is a race condition bug in the implementation.
> {noformat}
> 43789 WARN {} c.a.e.u.PreferredPathClassLoader - While loading class
> org.apache.hive.jdbc.HiveDatabaseMetaData, rethrowing unexpected
> java.lang.NullPointerException: Inflater has been closed
> java.lang.NullPointerException: Inflater has been closed
> at java.util.zip.Inflater.ensureOpen(Inflater.java:389)
> at java.util.zip.Inflater.inflate(Inflater.java:257)
> at java.util.zip.InflaterInputStream.read(InflaterInputStream.java:152)
> at java.io.BufferedInputStream.read1(BufferedInputStream.java:284)
> at java.io.BufferedInputStream.read(BufferedInputStream.java:345)
> at
> org.apache.commons.vfs2.util.MonitorInputStream.read(MonitorInputStream.java:91)
> at org.apache.commons.vfs2.FileUtil.getContent(FileUtil.java:47)
> at org.apache.commons.vfs2.impl.Resource.getBytes(Resource.java:102)
> at
> org.apache.commons.vfs2.impl.VFSClassLoader.defineClass(VFSClassLoader.java:179)
> at
> org.apache.commons.vfs2.impl.VFSClassLoader.findClass(VFSClassLoader.java:150)
> at
> com.atscale.engine.utils.PreferredPathClassLoader.findClass(PreferredPathClassLoader.scala:54)
> {noformat}
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