[OAK-6707] TarWriter.close() must not throw an exception on subsequent invocations

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 1.9.0, 1.10.0
• Component/s: segment-tar
• Labels: technical_debt
• Assignee: Michael Dürig
• Reporter: Michael Dürig
• Created: 22/Sep/17 14:34
• Updated: 26/Apr/18 13:22
• Resolved: 28/Feb/18 16:40

Description

Invoking TarWriter.close() on an already closed writer throws an ISE. According to the general contract this is not allowed:

* Closes this stream and releases any system resources associated
* with it. If the stream is already closed then invoking this
* method has no effect.

We should adjust the behvaviour of that method accordingly.

Failing to comply with that general contract causes TarWriter instances to fail in try-resource statements when multiple wrapped streams are involved.

Consider

try (
    StringWriter string = new StringWriter();
    PrintWriter writer = new PrintWriter(string);
    WriterOutputStream out = new WriterOutputStream(writer, Charsets.UTF_8))
{
    dumpHeader(out);
    writer.println("----------------------------------------");
    dumpHex(out);
    writer.println("----------------------------------------");
    return string.toString();
}

This code would cause exceptions to be thrown if e.g. the PrintWriter.close method would not be idempotent.