Hibernate recursive many-to-many association with the same entity

Question

Another Hibernate question... :P

Using Hibernate\'s Annotations framework, I have a User entity. Each User can have a collection of friends

Answer 1

Actually its very simple and could be achieved by following say you have following entity

public class Human {
    int id;
    short age;
    String name;
    List relatives;



    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public short getAge() {
        return age;
    }
    public void setAge(short age) {
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public List getRelatives() {
        return relatives;
    }
    public void setRelatives(List relatives) {
        this.relatives = relatives;
    }

    public void addRelative(Human relative){
        if(relatives == null)
            relatives = new ArrayList();
        relatives.add(relative);
    }




}

HBM for same:

And test case

import org.junit.Test;
import org.know.common.HBUtil;
import org.know.july31.hb.Human;

public class SimpleTest {

    @Test
    public void test() {
        Human h1 = new Human();
        short s = 23;
        h1.setAge(s);
        h1.setName("Ratnesh Kumar singh");
        Human h2 = new Human();
        h2.setAge(s);
        h2.setName("Praveen Kumar singh");
        h1.addRelative(h2);
        Human h3 = new Human();
        h3.setAge(s);
        h3.setName("Sumit Kumar singh");
        h2.addRelative(h3);
        Human dk = new Human();
        dk.setAge(s);
        dk.setName("D Kumar singh");
        h3.addRelative(dk);
        HBUtil.getSessionFactory().getCurrentSession().beginTransaction();
        HBUtil.getSessionFactory().getCurrentSession().save(h1);
        HBUtil.getSessionFactory().getCurrentSession().getTransaction().commit();
        HBUtil.getSessionFactory().getCurrentSession().beginTransaction();
        h1 = (Human)HBUtil.getSessionFactory().getCurrentSession().load(Human.class, 1);
        System.out.println(h1.getRelatives().get(0).getName());

        HBUtil.shutdown();
    }

}