Hibernate One to Many Select Query Example

Let us see the logic for hibernate one to many mapping select query,

hibernate one to many select means, if you select the parent object then automatically its corresponding child objects will also be selected, see i have given for the logic for selecting single parent object with all its childs & all parent objects with all child objects

But mates, ensure you came through these sessions for better understand

• Hibernate One-to-Many Mapping Insert
• Hibernate Relationships In Depth

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>

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>

Select Single Parent Object With All Child

OurLogic.java

package str;

import java.util.Iterator;
import java.util.Set;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
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();

Object o=session.get(Vendor.class, new Integer(100));
Vendor v=(Vendor)o;
System.out.println(v.getVendorId());
System.out.println(v.getVendorName());

Set s=v.getChildren();
Iterator it = s.iterator();

while(it.hasNext())
{

Object o1 = it.next();
Customer c = (Customer) o1;
System.out.println("---------------------------");
System.out.println("Customer objects...");
System.out.println("---------------------------");
System.out.println(c.getCustomerId());
System.out.println(c.getCustomerName());
System.out.println(c.getForevenId());
System.out.println("---------------------------");
}

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

}
}

If we want to select all the parent objects will all its corresponding child objects., then the logic will be like..

Select All Parent Objects With All Childs

OurLogic.java

package str;

import java.util.Iterator;
import java.util.List;
import java.util.Set;

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

public class OurLogicAllParents_AllChildrens {

public static void main(String args[])
{

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

SessionFactory factory = cfg.buildSessionFactory();
Session session = factory.openSession();

Query qry =session.createQuery("from Vendor v");
List l=qry.list();
Iterator it = l.iterator();

while(it.hasNext())
{

Object o = it.next();
Vendor v = (Vendor) o;
System.out.println(v.getVendorId()+ " " +v.getVendorName());

Set s= v.getChildren();
Iterator it1=s.iterator();

while(it1.hasNext())
{
Customer c = (Customer) it1.next();
System.out.println(c.getCustomerId()+" "+c.getCustomerName()+ " "+ c.getForevenId());

}

}

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

}
}

What you are thinkig....