Why maven assembly create manifest if file format is rar? - maven

Question

I have a Maven project with the following assembly descriptor:
<assembly
xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2 http://maven.apache.org/xsd/assembly-1.1.2.xsd">
<id>assemby-id</id>
<formats>
<format>rar</format>
</formats>
<includeBaseDirectory>false</includeBaseDirectory>
<files>
<file>
<source>${project.build.directory}/resources/file.txt</source>
<outputDirectory>/</outputDirectory>
</file>
</files>
If the format is rar, I get a folder META-INF with a manifest file in the rar.
Can someone explain why?

Answer 1

The maven-assembly-plugin does not support the rar archive format. Quoting the format documentation, the list of supported formats is:
"zip" - Creates a ZIP file format
"tar" - Creates a TAR format
"tar.gz" or "tgz" - Creates a gzip'd TAR format
"tar.bz2" or "tbz2" - Creates a bzip'd TAR format
"jar" - Creates a JAR format
"dir" - Creates an exploded directory format
"war" - Creates a WAR format
When the archiver encounters an unknown format, it defaults to jar and for this format, a META-INF directory is created by default.
As such, the assembly you have created is not a valid RAR file. It is in fact a JAR file.

Answer 2

The maven-assembly-plugin uses the maven-archiver for packaging. The maven-archiver adds a MANIFEST.MF to your package.
Update:
As mentioned here, you may configure the maven-archiver-plugin to leave out the DefaultImplementationEntries:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<configuration>
<archive>
<manifest>
<addDefaultImplementationEntries>false</addDefaultImplementationEntries>
</manifest>
</archive>
</configuration>
</plugin>