@MappedSuperclass
@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public interface ExerciseInterface {

	public abstract byte[] getImage();

	public abstract void setImage(byte[] image);

	public abstract String getName();

	public abstract String getReferenceUrl();

	public abstract void setName(String name);

	public abstract void setReferenceUrl(String referenceUrl);

	@ManyToOne
	public abstract ExerciseCategory getExerciseCategory();

	public abstract void setExerciseCategory(ExerciseCategory exerciseCategory);

	public abstract String getDescription();

	public abstract void setDescription(String description);

	@Id
	public abstract Long getId();

	public abstract void setId(Long id);

}
package zeuzgroup.core.exercise;

import javax.persistence.AttributeOverride;
import javax.persistence.AttributeOverrides;
import javax.persistence.Column;
import javax.persistence.Embedded;
import javax.persistence.Entity;
@Entity
@AttributeOverrides( {
		@AttributeOverride(name = "version", column = @Column(insertable = false, updatable = false)),
		@AttributeOverride(name = "id", column = @Column(insertable = false, updatable = false)) })

public  class ExerciseDuration extends ExerciseBase implements
		ExerciseInterface {
public ExerciseDuration() {
super(null);
}
	@Embedded
	private Duration duration;

	public ExerciseDuration(ExerciseCategory exerciseCategory) {
		super(exerciseCategory);
	}

	public Duration getDuration() {
		return duration;
	}

	public void setDuration(Duration duration) {
		this.duration = duration;
	}

}
package zeuzgroup.core.exercise;

import java.util.ArrayList;
import java.util.List;

import javax.persistence.Entity;
import javax.persistence.OneToMany;

import zeuzgroup.core.BaseEntity;

@Entity
public class ExerciseCategory extends BaseEntity {

	private String name;

	@OneToMany(mappedBy = "exerciseCategory")
	private List<ExerciseInterface> exercises = new ArrayList<ExerciseInterface>();

	public ExerciseCategory(String name) {
		super();
		this.name = name;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public List<ExerciseInterface> getExercises() {
		return exercises;
	}

	public void setExercises(List<ExerciseInterface> exercises) {
		this.exercises = exercises;
	}

	public ExerciseCategory() {
	}

}