Hibernate not creating a table

Question

I am new at Hibernate Annotations and I'd like to try an example.

I have two classes (Node and HyperEdge), when I run my application, it only creates a table for Node and not for HyperEdge.

This is the code I developed:

Node :

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="Node")
public class Node {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Integer id;

    @Column
    private String name;

    @Column(name="\"group\"")
    private Integer group;

    public Node() {
        super();
        // TODO Auto-generated constructor stub
    }

    public Node(Integer id, String name, Integer group) {
        super();
        this.id = id;
        this.name = name;
        this.group = group;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getGroup() {
        return group;
    }

    public void setGroup(Integer group) {
        this.group = group;
    }

}

HyperEdge :

import javax.persistence.Column;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Table(name="HyperEdge")
public class HyperEdge {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Integer id;

    @Column
    private String title;

    public HyperEdge() {
        super();
        // TODO Auto-generated constructor stub
    }
    public HyperEdge(Integer id, String title) {
        super();
        this.id = id;
        this.title = title;
    }
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }

}

hibernate.cfg.xml :

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>
        <!-- Database connection settings -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/exhiber</property>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>

        <property name="connection.pool_size">1</property>
        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="current_session_context_class">thread</property>
        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
        <property name="show_sql">true</property>
        <property name="hbm2ddl.auto">create</property>

        <mapping class="com.hib.ex.entity.Node" />
        <mapping class="com.hib.ex.entity.HyperEdge" />

    </session-factory>

</hibernate-configuration>

HibernateDao :

import java.util.List;

import org.hibernate.Session;
import org.hibernate.SessionFactory;

import com.hib.ex.entity.HyperEdge;
import com.hib.ex.entity.Node;

public class HibExDao {

    public void saveNode(Node noeud) {

        SessionFactory sf = HibExUtil.getSessionFactory();
        Session session = sf.openSession();
        session.beginTransaction();

        session.save(noeud);

        session.getTransaction().commit();
        session.close();

    }

    public List listNode() {

        SessionFactory sf = HibExUtil.getSessionFactory();
        Session session = sf.openSession();

        List nodes = session.createQuery("FROM Node").list();
        session.close();
        return nodes;

    }

    public Node readNode(Integer id) {

        SessionFactory sf = HibExUtil.getSessionFactory();
        Session session = sf.openSession();

        Node noeud = (Node) session.get(Node.class, id);
        session.close();
        return noeud;

    }

    public void saveHyperEdge(HyperEdge he, String chaine) {

        SessionFactory sf = HibExUtil.getSessionFactory();
        Session session = sf.openSession();
        session.beginTransaction();

        he.setTitle(chaine);

        session.save(he);
        session.getTransaction().commit();
        session.close();

    }

    public List listHyperEdge() {

        SessionFactory sf = HibExUtil.getSessionFactory();
        Session session = sf.openSession();

        List hyperedges = session.createQuery("FROM HyperEdge").list();
        session.close();
        return hyperedges;

    }

    public HyperEdge readHyperEdge(Integer id) {

        SessionFactory sf = HibExUtil.getSessionFactory();
        Session session = sf.openSession();

        HyperEdge hyperEdge = (HyperEdge) session.get(HyperEdge.class, id);
        session.close();
        return hyperEdge;

    }

}

The main class :

import java.util.List;

import com.hib.ex.dao.HibExDao;
import com.hib.ex.entity.HyperEdge;
import com.hib.ex.entity.Node;

public class Run {


    public static void main(String[] args) {

        HibExDao dao = new HibExDao();

        System.out.println("****************WRITING****************");
        Node n1 = new Node();
        n1.setName("toto");
        dao.saveNode(n1);
        System.out.println("Node saved!");
        Node n2 = new Node();
        n2.setName("lala");
        dao.saveNode(n2);
        System.out.println("Node saved!");

        System.out.println("\n****************READING****************");
        List nodes = dao.listNode();
        System.out.println("Name in Node number 2 is: " + dao.readNode(2).getName());

    }

}

What is the problem? And how can I fix it?

Thanks!

Answer 1

In HyperEdge class you have to add @Entity annotation so that hibernate can treat it as a entity to map with table HyperEdge in database.

@Entity
@Table(name="HyperEdge")
public class HyperEdge {

Answer 2

@Entity annotation to missing from your HyperEdge class

The @Entity annotation is used to mark this class as an Entity bean. So the class should atleast have a package scope no-argument constructor.

The @Table annotation is used to specify the table to persist the data. The name attribute refers to the table name. If @Table annotation is not specified then Hibernate will by default use the class name as the table name.

Answer 3

Perhaps you have to add @Entity annotation to your HyperEdge class