generating Eclipse project files with Maven

Question

When I try and generate the Eclipse project files using mvn eclipse:eclipse I get the following error:

Internal error in the plugin manager executing goal 'org.apache.maven.plugins:maven-eclipse-plugin:2.9-SNAPSHOT:eclipse': Unable to load the mojo 'org.apache.maven.plugins:maven-eclipse-plugin:2.9-SNAPSHOT:eclipse' in the plugin 'org .apache.maven.plugins:maven-eclipse-plugin'. A required class is missing: org/codehaus/plexus/resource/loader/ResourceNotFoundException

It appears that I'm using version 2.9-SNAPSHOT of the Maven Eclipse plugin. My guess is that there is a bug in this version of the plugin and if I use a stable release (instead of a snapshot), the problem will be resolved. Is there a way that I can change the version of this plugin I'm using, or is this problem unrelated to the version of the Eclipse plugin?

Answer 1

Either use the fully qualified name of the plugin to specify the version:

$ mvn org.apache.maven.plugins:maven-eclipse-plugin:2.8:eclipse

Or edit the ~/.m2/plugin-registry.xml file (for advanced users, make a backup).

Or try the -npr,--no-plugin-registry options to tell maven to not use ~/.m2/plugin-registry.xml for plugin versions:

$ mvn -npr eclipse:eclipse

But I don't guarantee a successful result. See the Introduction to the Plugin Registry for more details.

Or remove the version 2.9-SNAPSHOT from your local repository:

$ rm -rf ~/.m2/repository/org/apache/maven/plugins/maven-eclipse-plugin/2.9-SNAPSHOT

Answer 2

Unfortunately the problem still persists and the selected answer did not help me, as Maven always wanted to fetch the newest version available, which is the faulty 2.9-SNAPSHOT.

I had to manually specify the working version 2.8 in my POM, like so:

<plugin>
   <groupId>org.apache.maven.plugins</groupId>
   <artifactId>maven-eclipse-plugin</artifactId>
   <version>2.8</version>
   <configuration>
...

Answer 3

The solutions mentioned in the accepted answer does not seems to work. Using no plugin registry, it always tries to use the latest version, and re-download it you try to delete it.

I solved the problem by updating the file

.m2/repository/org/apache/maven/plugins/maven-eclipse-plugin/maven-metadata-central.xml

You're not supposed to edit this file, but if it was using the 2.9-SNAP instead of 2.9, it probably means that this file specified 2.9-SNAP at the latest instead of the 2.9