@Entity
@Table (name = "node")
public class Nodes
{
   @Id
   @GeneratedValue (strategy = GenerationType.IDENTITY)
   @Column(name="id")
   private int id;
   
   @Column (name = "question")
   private String question;
   
   @Column ( name = "result")
   private String result;
   
   @OneToOne(mappedBy="left_id")
   private Nodes left_id;
   
   @OneToOne(mappedBy="right_id")
   private Nodes right_id;   
   
   public Nodes(int id, String question, String result, Nodes left, Nodes right)
   {
          this.id=id;
          this.question=question;
          this.result=result;
          this.left_id=left;
          this.left_id=right;
   }
   
   public Nodes()
   {
      
   }
   
   public Nodes(String question)
   {
      this.question=question;
   }
   
   public Nodes(int id, String result)
   {
      this.id = id;
      this.result = result;
   }

   public void setId_node(int id_node)
   {
      this.id = id_node;
   }


   public int getId_node()
   {
      return id;
   }

   public void setQuestion (String question)
   {
      this.question = question;
   }
   
   public String getQuestion()
   {
      return this.question;
   }
   
   public void setResult (String unResult)
   {
      result = unResult;
   }
   
   public String getResult()
   {
      return this.result;
   }
   
   public Nodes getLeftNodes()
   {
      return left_id;
   }
   
   public void setLeftNodes(Nodes left)
   {
      this.left_id=left;
   }
   
   public Nodes getRightNodes()
   {
      return left_id;
   }
   
   public void setRifhtNodes(Nodes right)
   {
      this.right_id=right;
   }

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="com.beans.Nodes" table="node">
        <id name="id" type="int" access="field">
            <column name="id" />
            <generator class="assigned" />
        </id>
        <property name="question" type="java.lang.String">
            <column name="question" />
        </property>
        <property name="result" type="java.lang.String">
            <column name="result" />
        </property>
         
         <one-to-one name="left_id" class="com.beans.Nodes" access="field"></one-to-one>
        <one-to-one name="right_id" class="com.beans.Nodes" access="field"></one-to-one>
    </class>
</hibernate-mapping>