@Entity
@Table(name="TEST_USER")
public class User {
   
   private int id;
   private String name;
   private UserEnum type;
   private Map<AttributeInstance,UserAttribute> attributes=new HashMap<AttributeInstance,UserAttribute>();
   @Id
   @GeneratedValue(strategy=GenerationType.AUTO, generator="USER_GENERATOR")
   @SequenceGenerator(name="USER_GENERATOR", sequenceName="USER_SEQUENCE")
   @Column(name="ID")
   public int getId() {
      return id;
   }
   public void setId(int id) {
      this.id = id;
   }
   @Column(name="name")
   public String getName() {
      return name;
   }
   public void setName(String name) {
      this.name = name;
   }
   @Enumerated(EnumType.STRING)
   @Column(name="type")
   public UserEnum getType() {
      return type;
   }
   public void setType(UserEnum type) {
      this.type = type;
   }
   /**
    * @return the attributes
    */
   @OneToMany(cascade=CascadeType.ALL)
   @JoinColumn(name="USER_ID")
   @MapKey(name="attributeInstance")
   public Map<AttributeInstance, UserAttribute> getAttributes() {
      return attributes;
   }
   /**
    * @param attributes the attributes to set
    */
   public void setAttributes(Map<AttributeInstance, UserAttribute> attributes) {
      this.attributes = attributes;
   }

   public Object getAttribute(String name, int index) {
      return attributes.get(new AttributeInstance(name, index));
   }
}

@Entity
@Table(name="USER_ATTRIBUTE")
public class UserAttribute {

   private Integer id;
   private String value;
   private AttributeInstance attributeInstance=new AttributeInstance();
   /**
    * @return the id
    */
   @Id
   @Column(name="ID")
   @GeneratedValue(strategy=GenerationType.AUTO, generator="USERATT_GENERATOR")
   @SequenceGenerator(name="USERATT_GENERATOR", sequenceName="USERATT_SEQUENCE")
   public Integer getId() {
      return id;
   }
   /**
    * @param id the id to set
    */
   public void setId(Integer id) {
      this.id = id;
   }
   /**
    * @return the name
    */
   public String getName() {
      return attributeInstance.name;
   }
   /**
    * @param name the name to set
    */
   public void setName(String name) {
      this.attributeInstance.name = name;
   }
   /**
    * @return the value
    */
   public String getValue() {
      return value;
   }
   /**
    * @param value the value to set
    */
   public void setValue(String value) {
      this.value = value;
   }
   public AttributeInstance getAttributeInstance() {
      return attributeInstance;
   }
   /**
    * @param attributeInstance the attributeInstance to set
    */
   public void setAttributeInstance(AttributeInstance attributeInstance) {
      this.attributeInstance = attributeInstance;
   }
   /**
    * @return the index
    */
   public int getIdx() {
      return attributeInstance.index;
   }
   /**
    * @param index the index to set
    */
   public void setIdx(int index) {
      this.attributeInstance.index = index;
   }
   
}