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https://issues.apache.org/jira/browse/EXEC-122?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Marcono1234 closed EXEC-122.
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Fix Version/s: 1.4.1
Resolution: Fixed
Documentation has been adjusted to mention thread-safety requirements.
> PumpStreamHandler(OutputStream) constructor relies on stream being thread-safe
> ------------------------------------------------------------------------------
>
> Key: EXEC-122
> URL: https://issues.apache.org/jira/browse/EXEC-122
> Project: Commons Exec
> Issue Type: Bug
> Affects Versions: 1.4.0
> Reporter: Marcono1234
> Priority: Minor
> Fix For: 1.4.1
>
>
> h3. Description
> The constructor
> {{org.apache.commons.exec.PumpStreamHandler.PumpStreamHandler(OutputStream)}}
> which uses the {{OutputStream}} for both 'out' and 'err' currently does not
> perform any synchronization, so potentially two threads are writing at the
> same time to {{OutputStream}}.
> (This also applies to the other {{PumpStreamHandler}} constructor overloads
> in case the user manually provides the same {{OutputStream}} instance both as
> 'out' and 'err').
> This is error-prone because not all {{OutputStream}} implementations are
> thread-safe, and the user might not be aware of this behavior.
> So it would be good to either:
> - Mention in the {{PumpStreamHandler(OutputStream)}} documentation (and
> possibly for the other constructor overloads as well, if the same stream
> instance is used), that the {{OutputStream}} has to be thread-safe
> - Or, {{PumpStreamHandler}} (or {{StreamPumper}}) should perform
> synchronization, for example if the same stream instance is used by wrapping
> it in a custom synchronizing {{OutputStream}}
> (though maybe that is not desired if the stream is already thread-safe, e.g.
> {{Files.newOutputStream}})
> h3. Example
> Run this code snippet:
> {code}
> OutputStream out = new OutputStream() {
> @Override
> public void write(int b) throws IOException {
> System.out.println(Thread.currentThread().getName());
> }
> };
> PumpStreamHandler p = new PumpStreamHandler(out);
> p.setProcessOutputStream(new ByteArrayInputStream(new byte[1]));
> p.setProcessErrorStream(new ByteArrayInputStream(new byte[1]));
> p.start();
> Thread.sleep(1000);
> {code}
> You will see that it prints two different thread names. If you place a
> breakpoint at the {{println}} you will also see that no synchronization is
> performed, and the calls happen concurrently.
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