Daniel Janus created COMPRESS-652:
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Summary: Support appending to existing archives in
ZipArchiveOutputStream
Key: COMPRESS-652
URL: https://issues.apache.org/jira/browse/COMPRESS-652
Project: Commons Compress
Issue Type: New Feature
Reporter: Daniel Janus
h2. Problem
The Zip format is amenable to appending entries to an archive without having to
regenerate it from scratch. It is sufficient to read the central directory,
trim the archive just before it, add new entries, and then regenerate the
central directory at the end.
It isn't hard to add support for this to {{{}ZipArchiveOutputStream{}}}.
ZipFile can already read the central directory, so I envision a
{{ZipFile#append()}} method that would convert an already-created {{ZipFile}}
to a {{{}ZipArchiveOutputStream{}}}.
h2. Implementation
I've taken a stab at implementing this. My branch is
[here|https://github.com/nathell/commons-compress/tree/append-zip]. It works
well in my preliminary testing, but before this can be merged, it probably
needs some extra measures. For example, the current implementation won't work
with multipart archives, but doesn't check whether the origin ZipFile is
multipart. Also, I haven't tested zip64.
I'd love to receive feedback and work on making this mergeable! Java is not my
daily driver (Clojure is), so I might have violated some best practices.
h2. Context
I've encountered a need for this in an ETL-type system that repeatedly augments
a 'current' zip file with new changes ingested from external data sources.
Currently, I'm using ZipFileSystem, but it's suboptimal.
Other people are sometimes looking for this functionality; see
[here|https://stackoverflow.com/questions/2993847/append-files-to-an-archive-without-reading-rewriting-the-whole-archive?rq=1]
or
[here|https://stackoverflow.com/questions/2223434/appending-files-to-a-zip-file-with-java]
for examples.
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