[FIXED] How is default Maven plugin version decided?

Issue

I wonder when I did not specify a plugin version in some module's pom.xml like in:

<build>
...
<plugin>
   <groudId>org.apache.maven.plugins</groupId>
   <artifactId>maven-compiler-plugin</artifactId>
   <version>3.8.0</version>
</plugin>
...
</build>

What is the default plugin version used when I run "mvn compile"?

I have tried it and see actually it is using maven-compiler-plugin version 3.1 with above plugin element commented, my Maven version is 3.6.3.

I have spent 1 hour to google through Maven's documentation and related posts, but not find exact answer. I really like to know how that version is being decided?

Solution

The magic is not happening in the super pom, but in the so called bindings descriptor as available at https://github.com/apache/maven/blob/master/maven-core/src/main/resources/META-INF/plexus/default-bindings.xml. However, they are moving to the matching packaging plugin, for example for the maven-jar-plugin it is located at https://github.com/apache/maven-jar-plugin/blob/master/src/main/filtered-resources/META-INF/plexus/components.xml These versions haven't been updated, because it would be weird if 2 users with different Maven versions have different results (e.g. one has a broken build, the other not). Hence it is better to specify the plugin versions in the pom, don't rely of the defaults provided by Maven.

In the end it is all described at https://maven.apache.org/guides/introduction/introduction-to-the-lifecycle.html

Answered By - Robert Scholte