List<String> exclusions = new ArrayList<String>();

        for ( Dependency d : project.getDependencies() )
        {
            if ( d.getExclusions() != null )
            {
                for ( Exclusion e : d.getExclusions() )
                {
                    exclusions.add(  e.getGroupId() + ":" + e.getArtifactId() );
                }
            }
        }

import org.apache.maven.api.annotations.Experimental;
import org.apache.maven.api.annotations.Nullable;

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

    @Nullable
    String getArtifactId();

     */
    @Nullable
    Boolean getOptional();

    /**
     * {@return transitive dependencies to exclude}
     */
    @Nonnull
    Collection<Exclusion> getExclusions();