Hibernate Criteria Grouping Example

Hibernate Criteria Grouping Example

In this tutorial you will learn about the Hibernate Criteria Projection Grouping.

As we were using a 'group by' clause explicitly in HQL for grouping, there is no need to use this clause in Criteria query. In Criteria query for grouping projections certain types of projection are defined.

Click Here for Hibernate Criteria Ordering tutorial

Example

In the example given below I have used the Projections.groupProperty() for grouping the projections. We may use Property.forName() besides the built-in Projections with the setProjection() method. You can specify the number of columns by using the Projections.projectionList().add(Projections.property()).

Table goodsdealer

CREATE TABLE `goodsdealer` ( 
`goodsDealerId` int(15) NOT NULL, 
`orderedGoodsName` varchar(15) default NULL, 
`numOfGoodsOrder` int(20) default NULL, 
`priceOfGoods` int(10) default NULL 
) ENGINE=InnoDB DEFAULT CHARSET=latin1

GoodsDealer.java

package roseindia;

public class GoodsDealer {
private int goodsDealerId;
private int numOfGoodsOrder; 
private int priceOfGoods;
private String orderedGoodsName; 

public GoodsDealer()
{
super();
}
public GoodsDealer(int priceOfGoods, int goodsDealerId, int numOfGoodsOrder, String 
orderedGoodsName)
{ 
this.priceOfGoods = priceOfGoods;
this.goodsDealerId = goodsDealerId;
this.numOfGoodsOrder = numOfGoodsOrder;
this.orderedGoodsName = orderedGoodsName;
}
public int getPriceOfGoods() {
return priceOfGoods;
}
public void setPriceOfGoods(int priceOfGoods) {
this.priceOfGoods = priceOfGoods;
}
public int getGoodsDealerId() {
return goodsDealerId;
}
public void setGoodsDealerId(int goodsDealerId) {
this.goodsDealerId = goodsDealerId;
}
public int getNumOfGoodsOrder() {
return numOfGoodsOrder;
}
public void setNumOfGoodsOrder(int numOfGoodsOrder) {
this.numOfGoodsOrder = numOfGoodsOrder;
}
public String getOrderedGoodsName() {
return orderedGoodsName;
}
public void setOrderedGoodsName(String orderedGoodsName) {
this.orderedGoodsName = orderedGoodsName;
}
}

GoodsDealer.hbm.xml

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate mapping DTD//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="roseindia">
<class name= "GoodsDealer" table="goodsdealer">
<id name= "goodsDealerId" type="int" column="goodsDealerId">
</id>
<property name="numOfGoodsOrder">
<column name="numOfGoodsOrder"/>
</property>
<property name="orderedGoodsName">
<column name="orderedGoodsName"/>
</property>
<property name="priceOfGoods">
<column name="priceOfGoods"/>
</property>
</class>

</hibernate-mapping>

HibernateCriteriaGroupingExample.java

package roseindia;

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

import org.hibernate.Criteria;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.criterion.Projections;
import org.hibernate.criterion.Property;
import org.hibernate.criterion.Restrictions;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;

public class HibernateCriteriaGroupingExample {
private static SessionFactory sessionFactory;
private static ServiceRegistry serviceRegistry;

public static void main(String args[])
{
Session session = null;
try
{
try
{
Configuration cfg= new Configuration().addResource("roseindia/GoodsDealer.hbm.xml");
cfg.configure();
serviceRegistry = new ServiceRegistryBuilder().applySettings(cfg.getProperties()).buildServiceRegistry();
sessionFactory = cfg.buildSessionFactory(serviceRegistry);
}
catch(Throwable th)
{
System.err.println("Failed to create sessionFactory object."
+ th);
throw new ExceptionInInitializerError(th);
}
session = sessionFactory.openSession();
Criteria criteria = session.createCriteria(GoodsDealer.class);
// To group the rows in table goodsdealer
criteria.setProjection(Projections.projectionList()
.add(Projections.property("numOfGoodsOrder"))
.add(Projections.property("priceOfGoods"))
.add(Projections.groupProperty("priceOfGoods")));
// or it can be also written as 
//.add(Property.forName("priceOfGoods").group()));
List groupBy = criteria.list();
Iterator it = groupBy.iterator();
System.out.println("numOfGoodsOrder priceOfGoods");
while(it.hasNext())
{
Object[] obj = (Object[])it.next();
System.out.println(obj[0]+"\t\t "+ obj[1]);
} 
}
catch(Exception e)
{
System.out.println(e.getMessage());
}
finally
{
session.close();
}
}
}

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD//EN"
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
<session-factory>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.url">jdbc:mysql://192.168.10.13:3306/data
</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password">root</property>
<property name="hibernate.connection.pool_size">10</property>
<property name="show_sql">true</property>
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="hibernate.current_session_context_class">thread</property>
</session-factory>

</hibernate-configuration>

Output :

table goodsdealer

When you will execute the java file HibernateCrieteriaGroupingExample.java (RightClick -> RunAs -> Java Application) an output will be displayed on your console as :

INFO: HHH000399: Using default transaction strategy (direct JDBC transactions)
Mar 21, 2012 6:41:03 PM org.hibernate.hql.internal.ast.ASTQueryTranslatorFactory <init>
INFO: HHH000397: Using ASTQueryTranslatorFactory
Hibernate: select this_.numOfGoodsOrder as y0_, this_.priceOfGoods as y1_, this_.priceOfGoods as y2_ from goodsdealer this_ group by this_.priceOfGoods

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