public int hashCode() {
        int hash = 7;
        hash = 31 * hash + (this.groupId != null ? this.groupId.hashCode() : 0);
        hash = 31 * hash + (this.artifactId != null ? this.artifactId.hashCode() : 0);
        // ignore type
        hash = 31 * hash + (this.version != null ? this.version.hashCode() : 0);
        return hash;
    }