Hibernate mappedBy and ManyToMany Mapping with Annotations : Love Java Bytes

Project View After Completion :

Hibernate Environment Setting

Right click over project on Project Explorer and goto properties->Java Build Path->Libraries

Add Required Hibernate jars, JRE system Library, Apache Tomcat server by click on Add Library and Add External Jar ojdbc14.jar by click on Add External Jars.

For Details Read How to set Hibernate Environment

Student.java
This is pojo class where we are using @ManyToMany annotation for Many to Many mapping between Student and Books class.

 package blog.webideaworld.in;  
 import java.util.ArrayList;  
 import java.util.Collection;  
 import javax.persistence.Entity;  
 import javax.persistence.GeneratedValue;  
 import javax.persistence.Id;  
 import javax.persistence.ManyToMany;  
 import javax.persistence.Table;  
 @Entity  
 @Table(name="MyStudent")  
 public class Student {  
      @Id  
      @GeneratedValue  
      private int id;  
   private String name;  
   private int rollno;  
   @ManyToMany  
   private Collection<Books> books=new ArrayList<Books>();  
      public Collection<Books> getBooks() {  
           return books;  
      }  
      public void setBooks(Collection<Books> books) {  
           this.books = books;  
      }  
      public int getId() {  
           return id;  
      }  
      public void setId(int id) {  
           this.id = id;  
      }  
      public String getName() {  
           return name;  
      }  
      public void setName(String name) {  
           this.name = name;  
      }  
      public int getRollno() {  
           return rollno;  
      }  
      public void setRollno(int rollno) {  
           this.rollno = rollno;  
      }  
 }

Books.java
This is pojo class where we are using @ManyToMany annotation for Many to Many mapping between Student and Books class.
here we are using mappedBy because hibernate doesn't know that it is creating two same mapping table with different names from both sides and mappedBy will tell hibernate to not to create one extra relationship table with same attributes.

 package blog.webideaworld.in;  
 import java.util.ArrayList;  
 import java.util.Collection;  
 import javax.persistence.Entity;  
 import javax.persistence.GeneratedValue;  
 import javax.persistence.Id;  
 import javax.persistence.ManyToMany;  
 @Entity  
 public class Books {  
      @Id  
      @GeneratedValue  
      private int bookid;  
      private String bookname;  
      @ManyToMany(mappedBy="books")  
      private Collection<Student> student=new ArrayList<Student>();  
      public Collection<Student> getStudent() {  
           return student;  
      }  
      public void setStudent(Collection<Student> student) {  
           this.student = student;  
      }  
      public int getBookid() {  
           return bookid;  
      }  
      public void setBookid(int bookid) {  
           this.bookid = bookid;  
      }  
      public String getBookname() {  
           return bookname;  
      }  
      public void setBookname(String bookname) {  
           this.bookname = bookname;  
      }  
 }

ExeMain.java
It is working as Persistent class for Hibernate and the java class we are using to store object of Student and Books class using Hibernate Framework.

 package blog.webideaworld.in;  
 import org.hibernate.Session;  
 import org.hibernate.SessionFactory;  
 import org.hibernate.cfg.Configuration;  
 public class ExeMain {  
      public static void main(String args[]){  
           Student st =new Student();  
           st.setName("Suresh");  
        st.setRollno(44);  
        Books bk1=new Books();  
        bk1.setBookname("Let us C");  
        Books bk2=new Books();  
        bk2.setBookname("Let us C++");  
        st.getBooks().add(bk1);  
        st.getBooks().add(bk2);  
        bk1.getStudent().add(st);  
        bk2.getStudent().add(st);  
        @SuppressWarnings("deprecation")  
        SessionFactory sessionFactory     =new Configuration().configure("hibernate.cfg.xml").buildSessionFactory();  
        Session session=sessionFactory.openSession();  
        session.beginTransaction();  
        session.save(st);  
        session.save(bk1);  
        session.save(bk2);  
        session.getTransaction().commit();  
      }  
 }

hibernate.cfg.xml
This is a file that contains information about Oracle database(or any other database you want to use) Driver and connection information and mapping class information.

 <?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="hibernate.dialect">org.hibernate.dialect.OracleDialect</property>  
   <property name="hibernate.connection.driver_class">oracle.jdbc.OracleDriver</property>  
   <property name="hibernate.connection.url">jdbc:oracle:thin:@localhost:1521:xe</property>  
   <property name="hibernate.connection.username">hr</property>  
   <property name="hibernate.connection.password">hr</property>  
   <property name="hibernate.show_sql">true</property>  
   <property name="hibernate.hbm2ddl.auto">create</property>  
   <mapping class="blog.webideaworld.in.Student"/>  
   <mapping class="blog.webideaworld.in.Books"/>  
  </session-factory>  
 </hibernate-configuration>

Download Code Link 1
Download Code Link 2

To Run this Project Right Click inside ExeMain.java, select Run As -> Java Application

In output you can see default tablename and column names in MyStudent_Books is Student_id, books_bookid and if you want to override this default names then you can use @JoinTable,@JoinColumn Annotations.

Output:

MyStudent Table:

Books Table:

MyStudent_Books:

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Hibernate mappedBy and ManyToMany Mapping with Annotations

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