in src/main/java/org/apache/maven/resolver/internal/ant/types/Exclusion.java [51:65]
public void validate( Task task )
{
if ( isReference() )
{
getRef().validate( task );
}
else
{
if ( groupId == null && artifactId == null && classifier == null && extension == null )
{
throw new BuildException( "You must specify at least one of "
+ "'groupId', 'artifactId', 'classifier' or 'extension'" );
}
}
}