}

    protected static Metadata createMetadata(Artifact artifact, Versioning versioning) {
        Metadata metadata = new Metadata();
        metadata.setGroupId(artifact.getGroupId());
        metadata.setArtifactId(artifact.getArtifactId());
        metadata.setVersion(artifact.getVersion());
        metadata.setVersioning(versioning);
        return metadata;
    }

    /**
     * Gets the effective group identifier of the model.
     *
     * @return The effective group identifier of the model or an empty string if unknown, never {@code null}.
     */
    public String getGroupId() {
        return (groupId != null) ? groupId : "";
    }

    /**
     * Sets the effective group identifier of the model.
     *

    @Override
    public boolean include(Artifact artifact) {
        String id = artifact.getArtifactId();

        if (excludes.contains(id)) {
            return false;
        }

        id = artifact.getGroupId() + ':' + id;

        return !excludes.contains(id);
    }

    @Override
    public int hashCode() {
        int hash = 17;
        hash = hash * 31 + excludes.hashCode();
        return hash;
    }

        }
    }

    @Test
    void testBuildReader() throws Exception {
        PluginDescriptor pd = build("/plugin.xml");

        assertEquals("org.apache.maven.plugins", pd.getGroupId());
        assertEquals("maven-jar-plugin", pd.getArtifactId());
        assertEquals("2.3-SNAPSHOT", pd.getVersion());
        assertEquals("jar", pd.getGoalPrefix());

        if (system) {
            props = Collections.singletonMap(MavenArtifactProperties.LOCAL_PATH, dependency.getSystemPath());
        }

        Artifact artifact = new DefaultArtifact(
                dependency.getGroupId(),
                dependency.getArtifactId(),
                dependency.getClassifier(),
                null,
                dependency.getVersion(),
                props,
                stereotype);

/**
 * A dependency exclusion.
 *
 * @since 4.0.0
 * @see DependencyCoordinates#getExclusions()
 */
@Experimental
public interface Exclusion {
    @Nullable
    String getGroupId();

    @Nullable
    String getArtifactId();

    //
    // ----------------------------------------------------------------------

    public PluginDescriptor() {}

    public PluginDescriptor(PluginDescriptor original) {
        this.setGroupId(original.getGroupId());
        this.setArtifactId(original.getArtifactId());
        this.setVersion(original.getVersion());
        this.setGoalPrefix(original.getGoalPrefix());

        }
    }

    protected void mergeModel_GroupId(Model target, Model source, boolean sourceDominant, Map<Object, Object> context) {
        String src = source.getGroupId();
        if (src != null) {
            if (sourceDominant || target.getGroupId() == null) {
                target.setGroupId(src);
                target.setLocation("groupId", source.getLocation("groupId"));
            }
        }
    }

        }
    }

    @Override
    public boolean isMerged() {
        return merged;
    }

    @Override
    public String getGroupId() {
        return emptify(metadata.getGroupId());
    }

    @Override
    public String getArtifactId() {
        return metadata.storedInGroupDirectory() ? "" : emptify(metadata.getArtifactId());
    }

    @Override

        this.message = (message != null && !message.isEmpty()) ? message : null;
    }

    @Override
    public String getGroupId() {
        if (groupId != null) {
            return groupId;
        } else {
            return artifact.getGroupId();
        }
    }

    @Override
    public String getArtifactId() {
        if (artifactId != null) {
            return artifactId;