Hibernate One to Many Mapping Insert Query Example

One-to-Many:  according to database terminology, one row of table related with multiple rows of other table

[or]

According to hibernate, one object of one pojo class related to multiple objects of other pojo

I mean, one [parent] to many [Children], example of one-to-many is some thing category books contains different type of books, one vendor contains lot of customers bla bla.

To achieve one-to-many between two pojo classes in the hibernate, then the following two changes are required

• In the parent pojo class, we need to take a collection property, the collection can be either Set,List,Map (We will see the example on separate collection later)
• In the mapping file of that parent pojo class, we need to configure the collection

I will take this vendor-customer as an example..

Hibernate One-To-Many Insert Query

files required…

• Vendor.java [pojo class]
• Customer.java [pojo class]
• OurLogic.java
• Customer.hbm.xml
• hibernate.cfg.xml
• Vendor.hbm.xml

Vendor.java

package str;

import java.util.Set;

public class Vendor {

private int vendorId;
private String vendorName;
private Set children;

public int getVendorId() {
return vendorId;
}
public void setVendorId(int vendorId) {
this.vendorId = vendorId;
}
public String getVendorName() {
return vendorName;
}
public void setVendorName(String vendorName) {
this.vendorName = vendorName;
}
public Set getChildren() {
return children;
}
public void setChildren(Set children) {
this.children = children;
}

}

Customer.java

package str;
public class Customer {

private int customerId;
private String customerName;
private int forevenId;

public int getCustomerId() {
return customerId;
}
public void setCustomerId(int customerId) {
this.customerId = customerId;
}
public String getCustomerName() {
return customerName;
}
public void setCustomerName(String customerName) {
this.customerName = customerName;
}

public int getForevenId() {
return forevenId;
}
public void setForevenId(int forevenId) {
this.forevenId = forevenId;
}

}

Customer.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
<class name="str.Customer" table="customer">

<id name="customerId" column="custid"  />
<property name="customerName" column="custname" length="10"/>

<property name="forevenId" column="forevenid"  insert="false" />

</class>
</hibernate-mapping>

Vendor.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
<class name="str.Vendor" table="vendor">

<id name="vendorId" column="vendid"  />
<property name="vendorName" column="vendname" length="10"/>

<set name="children" cascade="all" >

<key column="forevenid" />
<one-to-many class="str.Customer" />

</set>

</class>
</hibernate-mapping>

See line number 12,  this time i used one new attribute cascade=”all” we will see about this attribute later as separate topic.

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 resource="Customer.hbm.xml"></mapping>
<mapping resource="Vendor.hbm.xml"></mapping>
</session-factory>
</hibernate-configuration>

OurLogic.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 OurLogic {

public static void main(String args[])
{

Configuration cfg = new Configuration();
cfg.configure("hibernate.cfg.xml");

SessionFactory factory = cfg.buildSessionFactory();
Session session = factory.openSession();
//parent object
Vendor v =new Vendor();

v.setVendorId(101);
v.setVendorName("java4s");

//creating 3 child objects
Customer c1=new Customer();

c1.setCustomerId(504);
c1.setCustomerName("customer4");

Customer c2=new Customer();

c2.setCustomerId(505);
c2.setCustomerName("customer5");

Customer c3=new Customer();

c3.setCustomerId(506);
c3.setCustomerName("customer6");

// adding child objects to set, as we taken 3rd property set in parent
Set s=new HashSet();

s.add(c1);
s.add(c2);
s.add(c3);

v.setChildren(s);

Transaction tx = session.beginTransaction();

session.save(v);

tx.commit();
session.close();
System.out.println("One To Many is Done..!!");
factory.close();

}
}

Notes:

• In Vendor.java, we have taken a property of type Set
• In Customer.java, we have taken one property forevenId of type int to insert Vendor id

In the database

Regarding Vendor.hbm.xml

• In this mapping file, we used a collection configuration element (Set), because in pojo class of vendor, we used the collection type as Set, (we can use Map,List too)
• In order to transfer 0perations on parent object to child object we need to add cascade attribute
• By default, cascade value is none, it means even though relationship is exist, the operations we are doing on parent will not transfer to child, i mean to say here operations are insert, delete, update
• In our Vendor.hbm.xml,  we used cascade =”all” means all operations at parent object will be transfer to child
• while applying relationships, we need to configure the foreign key column name, by using which the relationship is done
• Inthe mapping file, we need to use <key /> eliment to configure foregin key column name, in this example forevenid is foreign key
• <one-to-many> is child class with which relation been done,  in our example str.Customer is the class [str is the package]

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::. About the Author .::
		Sivateja Kandula - Java/J2EE Full Stack Developer Founder of Java4s - Get It Yourself, A popular Java/J2EE Programming Blog, Love Java and UI frameworks. You can sign-up for the Email Newsletter for your daily dose of Java tutorials.