Caused by: Exception [EclipseLink-7151] (Eclipse Persistence Services - 2.4.1.v20121003-ad44345): org.eclipse.persistence.exceptions.ValidationException
Exception Description: The type [class commons.Gender] for the attribute [gender] on the entity class [class persistence.PatientEntity] is not a valid type for an enumerated mapping. The attribute must be defined as a Java enum.

public class PatientEntity implements Lockable<Long>, Identifiable<Long> {
  ...
  private Gender gender;

  @Enumerated(EnumType.STRING)
  @Column(name = "gender")
  public Gender getGender() {
    return this.gender;
  }

  public void setGender(Gender gender) {
    this.gender = gender;
  }
  ...
}

public enum Gender implements ExtendedDisplayable {

	NONE,
	MALE,
	FEMALE;

  ...
}