question: are jar files compressed?

[avkonst]

• I would like to understand if jar files, produced by the plugin, are compressed? It seems they are copied as is from the maven repository.
• How can I change the compression level? If it is not possible, would it be possible to add this feature?

Clarification: my goal is to produce the smallest-footprint of working java application (footprint is measured by the size of unpacked tarball content produced by the universal build).

Information

• What sbt-native-packager are you using
  Universal
• What sbt version
  0.13.x
• What is your build system (e.g. Ubuntu, MacOS, Windows, Debian )
  Windows, Ubuntu
• What package are you building (e.g. docker, rpm, ...)
  zip tarbals
• What is your target system (e.g. Ubuntu 16.04, CentOS 7)
  java (OS independent)

[muuki88]

Hi. Thanks for your question.

native-packager doesn't alter the resulting jars in any way. It takes it as sbt produces them via the packageBin task. IIRC jars are actually zip files so they are already compressed.

@dwijnand may know more about the packageBin task?

[dwijnand]

Yeah jar files are glorified zips, so mildly compressed.

I did hear a rumour though that there's an alternative, better compression algorithm that was merged into the jdk years and years ago but no-one uses. If better compression is your need, maybe you should look into that claim.

[muuki88]

Thanks @dwijnand 😄

@avkonst if you find something interesting regarding a better jar compression, it would be awesome if you share it here and repopen the issue. Maybe there is a way to integrate it in native-packager.

[matanox]

At the core, do all jars built with sbt package and sbt assembly (using Java 8) compress all files included in them?

[muuki88]

neither of those tasks are part of sbt-native-packager.

sbt assembly comes from the sbt-assembly plugin and package is IIRC from sbt itself.