@Entity
@Table(name="protocol_item")
@AttributeOverrides(
{
@AttributeOverride(name="ID",column=@Column(name="id"))
}
)
@SequenceGenerator(name = "seq", sequenceName = "protocol_item_id_seq")
public class protocolItem extends annotableBiotype implements binary_attachable, Comparable {


   
//...
//many stuff left out here!


    private protocolVersion version = null;

 
    /**
     * @return the version
     */
 
// This embedded class is causing the trouble
    @Embedded
    public protocolVersion getProtocolVersion() {
        if (this.version==null){
           this.version =  new protocolVersion();
        }
        return version;
    }

    /**
     * @param version the version to set
     */
    public void setProtocolVersion(protocolVersion version) {
        this.version = version;
    }

   @ManyToOne
    @JoinColumn(name="summary")
    public protocolSummary getSummary() {
        return summary;
    }

//more stuff left out here...
//which all works fine...

   }

@Embeddable
public class protocolVersion implements Comparable, Serializable {

    private int major =1;

    private int minor = 0;

    /**
     * @return the major
     */
    public int getMajorversion() {
        return major;
    }

    /**
     * @param major the major to set
     */
    public void setMajorversion(int major) {
        this.major = major;
    }

    /**
     * @return the minor
     */
    public int getMinorversion() {
        return minor;
    }

    /**
     * @param minor the minor to set
     */
    public void setMinorversion(int minor) {
        this.minor = minor;
    }

    @Override
  public String toString(){
    StringBuffer bfr = new StringBuffer();
    bfr.append(this.getMajorversion());
    bfr.append(".");
    bfr.append(this.getMinorversion());
      return bfr.toString();
  }


public int compareTo(Object o){
    if (o == null){
        return 1;
    }
    if (o == this){
        return 0;
    }
    protocolVersion v = (protocolVersion)o;
    int bfr = 0;
    bfr = this.getMajorversion()-v.getMajorversion();
    if (bfr != 0){
        return bfr;
    } else {
        return this.getMinorversion()-v.getMinorversion();
    }
}

public boolean equals(Object o){
   return this.compareTo(o)==0;
}


    @Override
    public int hashCode() {
        int hash = 5;
        hash = 71 * hash + this.major;
        hash = 71 * hash + this.minor;
        return hash;
    }



}

CREATE TABLE protocol_item
(
  id serial NOT NULL,
  summary character varying(80) NOT NULL,
   majorversion integer NOT NULL DEFAULT 1,
  minorversion integer NOT NULL DEFAULT 0,
  CONSTRAINT protocol_item_pkey PRIMARY KEY (id),
   CONSTRAINT protocol_item_summary_fkey FOREIGN KEY (summary)
      REFERENCES protocol_summaries (id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION,
  CONSTRAINT protocol_item_summary_key UNIQUE (summary, majorversion, minorversion)
)

java.lang.StackOverflowError
        at org.hibernate.cfg.AbstractPropertyHolder.getOverriddenColumn(AbstractPropertyHolder.java:77)
        at org.hibernate.cfg.ComponentPropertyHolder.getOverriddenColumn(ComponentPropertyHolder.java:105)
        at org.hibernate.cfg.AbstractPropertyHolder.getOverriddenColumn(AbstractPropertyHolder.java:79)
        at org.hibernate.cfg.ComponentPropertyHolder.getOverriddenColumn(ComponentPropertyHolder.java:105)
        at org.hibernate.cfg.AbstractPropertyHolder.getOverriddenColumn(AbstractPropertyHolder.java:79)
        at org.hibernate.cfg.ComponentPropertyHolder.getOverriddenColumn(ComponentPropertyHolder.java:105)
        (...many more of the same...)

SessionFactory sf = new AnnotationConfiguration().configure().buildSessionFactory();

        if (this.version==null){
           this.version =  new protocolVersion();
        }