Consider this entity:

@Entity
@Table(
    uniqueConstraints = {
        @UniqueConstraint(name = "uk_language_name", columnNames = { "name" })
    }
)
public class Language {
    @Id
    @GeneratedValue(strategy = IDENTITY)
    public Integer languageId;

    @Column(unique = true)
    public String name;
}

It contains redundant uniqueness information on the name column, via @UniqueConstraint and @Column(unique = true). The @UniqueConstraint specifies a name. Yet, when generating DDL from this table using SchemaExport, the name is not taken into consideration, but a synthetic name is generated for the unique constraint.