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Example of @ManyToOne in Hibernate

By Arvind Rai, May 21, 2013
@ManyToOne in hibernate creates the association between two entities in such a way that more than one entity can be associated with single entity. These is called Many-to-one association in hibernate. The example of Many-to-one can be that more than one student may associates with single college, Many citizen lives in single country etc. Syntax is
 @ManyToOne( cascade = CascadeType.ALL )
 @JoinColumn(name="cloumnId")
 
Find the complete example.

Student.java
package com.concretepage.persistence;
import java.io.Serializable;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
@Entity
@Table(name="student")
public class Student implements Serializable{
      private static final long serialVersionUID = 1L;
      @Id
      @Column(name="std_id")
      private int studentId;

      @Column(name="std_name")
      private String studentName;

      @ManyToOne( cascade = CascadeType.ALL )
      @JoinColumn(name="col_id")
      private College college;
      public Student(int studentId,String studentName,College college){
		this.studentId=studentId;
		this.studentName=studentName;
		this.college=college;
      }
      public Student(){
      }
      public int getStudentId() {
         return studentId;
      }
      public void setStudentId(int studentId) {
         this.studentId = studentId;
      }
      public String getStudentName() {
          return studentName;
      }
      public void setStudentName(String studentName) {
         this.studentName = studentName;
      }
      public College getCollege() {
         return college;
      }
      public void setCollege(College college) {
         this.college = college;
      }
}
 


College.java
package com.concretepage.persistence;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name="college")
public class College implements Serializable {
	        private static final long serialVersionUID = 1L;
		@Id
		@Column(name="col_id")
		private int colId;

    	        @Column(name="col_name")
		private String collegeName;

		@Column(name="student_num")
		private int numStudent;
		public College(){
		}
		public College(int colId,String collegeName,int numStudent){
			this.colId=colId;
			this.collegeName=collegeName;
			this.numStudent=numStudent;
		}
		public int getColId() {
			return colId;
		}
		public void setColId(int colId) {
			this.colId = colId;
		}
		public String getCollegeName() {
			return collegeName;
		}
		public void setCollegeName(String collegeName) {
			this.collegeName = collegeName;
		}
		public int getNumStudent() {
			return numStudent;
		}
		public void setNumStudent(int numStudent) {
			this.numStudent = numStudent;
		}
}
 


HibernateUtil.java
package com.concretepage.util;
import java.util.Properties;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;

import com.concretepage.persistence.College;
import com.concretepage.persistence.Student;
public class HibernateUtil {
	private static final SessionFactory concreteSessionFactory;
		static {
		 try {
			    Properties prop= new Properties();
			    prop.setProperty("hibernate.connection.url", "jdbc:mysql://localhost:3306/hibernate");
			    prop.setProperty("hibernate.connection.username", "root");
			    prop.setProperty("hibernate.connection.password", "");
			    prop.setProperty("hibernate.hbm2ddl.auto", "update");
			    prop.setProperty("dialect", "org.hibernate.dialect.MySQLDialect");
				
			    concreteSessionFactory = new AnnotationConfiguration()
			   .addPackage("com.concretepage.persistence")
					   .addProperties(prop)
					   .addAnnotatedClass(College.class)
					   .addAnnotatedClass(Student.class)
					   .buildSessionFactory();
		  } catch (Throwable ex) {
			throw new ExceptionInInitializerError(ex);
		  }
		}
		public static Session getSession()
				throws HibernateException {
			return concreteSessionFactory.openSession();
		}
		
		public static void main(String... args){
			Session session=getSession();
			session.beginTransaction();

			College college=new College(1,"BHU",1000);
			Student s= new Student(1,"Ram",college);
			session.persist(s);

			Student s2= new Student(2,"Shyam",college);
			session.persist(s2);
			session.getTransaction().commit();
	   }
	}
 


Output

Example of @ManyToOne in Hibernate
POSTED BY
ARVIND RAI
ARVIND RAI
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