Hibernate Many To Many Mapping Using Annotations

Let us see the example on many to many using annotations

Files required….

• Categories.java
• Item.java
• hibernate.cfg.xml
• ForOurLogic.java

Categories.java

package str;

import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;
import javax.persistence.Table;

@Entity
@Table(name="categories")
public class Categories
{
	@Id
	@Column(name="catid")
	 private int categoryId;
	@Column(name="catname",length=10)
	private String categoryName;
	@ManyToMany(targetEntity=Item.class,cascade=CascadeType.ALL)
	@JoinTable(name="categories_items",joinColumns=@JoinColumn(name="cat_id_fk",referencedColumnName="catid"),inverseJoinColumns=@JoinColumn(name="item_id_fk",referencedColumnName="itemid"))
	private Set items;

	public int getCategoryId() {
		return categoryId;
	}
	public void setCategoryId(int categoryId) {
		this.categoryId = categoryId;
	}
	public Set getItems() {
		return items;
	}
	public void setItems(Set items) {
		this.items = items;
	}
	public String getCategoryName() {
		return categoryName;
	}
	public void setCategoryName(String categoryname) {
		this.categoryName = categoryname;
	}

}

Item.java

package str;

import java.util.Set;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.ManyToMany;
import javax.persistence.Table;

@Entity
@Table(name="items")
public class Item
{
	@Id
	@Column(name="itemid")
	private int itemId;
	@Column(name="itemname",length=10)
	private String itemName;
	@ManyToMany(targetEntity=Categories.class,mappedBy="items")
	private Set  categories;

	public Set getCategories() {
		return categories;
	}
	public void setCategories(Set  categories) {
		this.categories = categories;
	}
	public int getItemId() {
		return itemId;
	}
	public void setItemId(int itemId) {
		this.itemId = itemId;
	}
	public String getItemName() {
		return itemName;
	}
	public void setItemName(String itemName) {
		this.itemName = itemName;
	}
}

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>
<property name="connection.driver_class">oracle.jdbc.driver.OracleDriver
</property>
<property name="connection.url">jdbc:oracle:thin:@www.java4s.com:1521:XE</property>
<property name="connection.username">system</property>
<property name="connection.password">admin</property>

<property name="dialect">org.hibernate.dialect.OracleDialect</property>
<property name="show_sql">true</property>
<property name="hbm2ddl.auto">update</property>

<mapping></mapping>
<mapping></mapping>
</session-factory>
</hibernate-configuration>

ForOurLogic.java

package str;

import java.util.HashSet;
import java.util.Set;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class ForOurLogic { 

	public static void main(String args[])
	{
		Configuration cfg = new Configuration();
		cfg.configure("hibernate.cfg.xml"); 

		SessionFactory factory = new Configuration().configure().buildSessionFactory();
		Session ses = factory.openSession();	

		Categories c1 = new Categories();
		c1.setCategoryId(1);
		c1.setCategoryName("cat 1");

		Categories c2=new Categories();
		c2.setCategoryId(2);
		c2.setCategoryName("cat 2");

		Item i1=new Item();
		Item i2 = new Item();

		i1.setItemId(101);
		i1.setItemName("item1");

		i2.setItemId(102);
		i2.setItemName("item2");

		Set  s =new HashSet();
		s.add(i1);
		s.add(i2);

		c1.setItems(s);
		c2.setItems(s);

		Transaction tx = ses.beginTransaction();
		ses.save(c1);
		ses.save(c2);
		tx.commit();
		System.out.println("Man to Many using annotations been done...!!!!!");
		ses.close();
	}

}

Eclipse Output

In the database

What you are thinkig....