This exception notifies you of a deeper problem while trying to load a goal from its plugin class path. Possible causes for this can be:
- The JAR or POM of the plugin or any of its dependencies got corrupted while being downloaded from the plugin repository to your local repository. For instance, if the plugin class path is missing some dependencies of the plugin, this can result in linkage errors that prevent the instantiation of the goal.
- You specified custom dependencies for the plugin in your POM which are not compatible with the plugin.
- The plugin was not properly assembled by its creator.
To check whether the plugin JAR and its POM are intact, inspect your local repository which is usually located at ${user.home}/.m2/repository. For a plugin with the coordinates com.company:custom-maven-plugin:1.0, the file to check is com/company/custom-maven-plugin/1.0/custom-maven-plugin-1.0.jar and custom-maven-plugin-1.0.pom, respectively. If those files don't match the copies in the plugin repository, e.g. as noticeable by checksum mismatches, simply delete the local files and have Maven re-download it.
In case of custom plugin dependencies, please verify that the version of the custom dependencies you specified are compatible with the plugin version you employ. One way to do this is to check the versions of the dependencies that the plugin natively uses. For a plugin site that is generated by Maven, this information can be accessed via "Project Information" > "Dependencies" from the left navigation bar. The documentation for many common Maven plugins can be reached via our plugin index.