Do `.kar` files need `META-INF/MANIFEST.MF`?

[dilyanpalauzov]

It is unclear from https://karaf.apache.org/manual/latest/kar if a .kar file needs META-INF/MANIFEST.MF.

On the one side the spring-4.0.0.kar example contains META-INF/MANIFEST.MF. On the other side the next paragraps says

As a KAR file is a simple zip file, you can create the KAR file by hand.

For instance, the following Unix commands create a very simple KAR file:

~$ mkdir repository
~$ cp /path/to/features.xml repository/features.xml
~$ cp /path/to/my.jar repository/my/project/my/1.0.0/my-1.0.0.jar
~$ zip -r my.kar repository
updating: repository/ (stored 0%)
  adding: repository/my/project/my/1.0.0/my-1.0.0.jar (deflated 0%)

• my.kar does not contain META-INF/MANIFEST.MF
• In a test I created locally, mvn install karaf:kar creates a .kar file and it contains under META-INF/MANIFEST.MF:

Manifest-Version: 1.0
Created-By: Kar Maven Plugin 4.4.8
Build-Jdk-Spec: 21

So does a .kar file need a META-INF/MANIFEST.MF? If yes, then what purpose does it serve and what shall be included there? If no, why does Kar Maven Plugin 4.4.8 include it?

[jbonofre]

Kar doesn't strictly require META-INF/MANIFEST.MF, it's a zip archive like a jar.
The karaf-maven-plugin is using the jar archiver, which generate/include MANIFEST.MF (for information purpose in this case).
What's the issue about MANIFEST.MF ?

[dilyanpalauzov]

Some examples include MANIFEST.MF, other examples do not include MANIFEST.MF. The issue is that this inconsistency raises questions.

It would be reasonable to spell, that a META-INF/MANIFEST.MF file is included in the .kar file by karaf-maven-plugin, but that file is not evaluated by Karaf.