Caused by: org.hibernate.AnnotationException: Property org.portfolio.data.ReportElement.content has an unbound type and no explicit target entity. Resolve this Generic usage issue or set an explicit target attribute (eg @OneToMany(target=) or use an explicit @Type
   at org.hibernate.cfg.AnnotationBinder.addElementsOfAClass(AnnotationBinder.java:1032)
   at org.hibernate.cfg.AnnotationBinder.getElementsToProcess(AnnotationBinder.java:882)
   at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:667)
   at org.hibernate.cfg.AnnotationConfiguration.processArtifactsOfType(AnnotationConfiguration.java:546)
   at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:291)
   at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1333)
   at org.hibernate.cfg.AnnotationConfiguration.buildSessionFactory(AnnotationConfiguration.java:867)
   at org.portfolio.data.hibernate.HibernateUtil.<clinit>(HibernateUtil.java:36)

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@Table(name = "ReportElement")
public abstract class ReportElement<T, E> implements Serializable,
      Comparable<ReportElement<T, E>> {

   private static final long serialVersionUID = 1L;

   protected T content;

   @Id
   @GeneratedValue
   @ManyToOne
   @JoinColumn(name = "element_fk", insertable = false, updatable = false)
   private long Id;

   protected E status;

   public abstract void addContent(T Content);

   public abstract int compareTo(final ReportElement<T, E> o);

   public abstract T getContent();

   public long getId() {
      return this.Id;
   }

   public abstract E getStatus();

   public abstract void setContent(final T content);

   public void setId(final long id) {
      this.Id = id;
   }

   public abstract void setStatus(final E status);

}

@Entity
@Table(name = "ReportElementSingleContent")
public class ReportElementSingleContent extends ReportElement<String, Boolean> {

   private static final long serialVersionUID = 1L;

   @Override
   @Column(nullable = false)
   public void addContent(final String Content) {
      super.content = this.content;
   }

   public void addInformations(final String content, final Boolean status) {
      this.setContent(content);
      this.setStatus(status);
   }


   @Override
   public int compareTo(final ReportElement<String, Boolean> o) {
      return 0;
   }


   @Override
   public String getContent() {
      return super.content;
   }

   @Override
   @Column(nullable = false)
   public Boolean getStatus() {
      return super.status;
   }

   @Override
   public void setContent(final String content) {
      super.content = content;
   }

   @Override
   public void setStatus(final Boolean status) {
      super.status = status;

   }
}

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@SequenceGenerator(name = AbstractEntity.GENERATOR, sequenceName = "S_TRACEABLE_ENTITY")
public abstract class TraceableEntity<S extends Enum<S> & Status>  extends AbstractEntity {

    @Enumerated(EnumType.STRING)
    private S status;

    ...
}