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JPA Avg Function
Posted on: March 17, 2005 at 12:00 AM

In this section, you will learn the avg of aggregate function. This method calculate an average of given data.

JPA Avg Function

In this section, you will learn the avg of aggregate function. This method calculate an average of given data.

JPA Avg() function:

Query query=em.createQuery
("SELECT p FROM Product p WHERE p.price >
(SELECT AVG(p.price) FROM p)");

This query select all records from the product table which have the product price is grater than the average of product price.

For this application, you need the following artifacts:

Database Table: product
Model Class: Product.java
Main Class: JPAAvgFunction.java

Database Table: product

CREATE TABLE `product` (
`id` int(11) NOT NULL auto_increment,
`itemName` varchar(50) NOT NULL,
`price` double NOT NULL,
PRIMARY KEY (`id`)
)

Model Class: Product.java

/**
*
*/
package roseindia;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

/**
* @author Administrator
*
*/
@Entity
@Table(name="product")
public class Product {

@Id
@GeneratedValue
private int id;
/**
* @return the id
*/
public int getId() {
return id;
}

/**
* @param id the id to set
*/
public void setId(int id) {
this.id = id;
}

@Column(name="itemName",length=50,nullable=false)
private String itemName;
/**
* @return the itemName
*/
public String getItemName() {
return itemName;
}

/**
* @param itemName the itemName to set
*/
public void setItemName(String itemName) {
this.itemName = itemName;
}

@Column(name="price")
private double price;
/**
* @return the price
*/
public double getPrice() {
return price;
}

/**
* @param price the price to set
*/
public void setPrice(double price) {
this.price = price;
}

}

Main Class: JPAAvgFunction.java

/**
* 
*/
package roseindia;

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

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;
import javax.persistence.Query;

/**
* @author Administrator
*
*/
public class JPAAvgFunction {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub

EntityManagerFactory emf=Persistence.createEntityManagerFactory("jpa");
EntityManager em=emf.createEntityManager();
try{
EntityTransaction entr=em.getTransaction();
entr.begin();
Query query=em.createQuery("SELECT p FROM Product p WHERE p.price > (SELECT AVG(p.price) FROM p)");
List pList=query.getResultList();
Iterator pIterator=pList.iterator();
while(pIterator.hasNext()){
Product pro=(Product)pIterator.next();
System.out.print("Item Name:"+pro.getItemName());
System.out.print(" Price:"+pro.getPrice());
System.out.println();
}
entr.commit();
}
finally{
em.close();
}
}
}

Output:

log4j:WARN No appenders could be found for logger
(org.hibernate.cfg.annotations.Version).

log4j:WARN Please initialize the log4j system properly.

Hibernate: select product0_.id as id1_, product0_.itemName
as itemName1_, product0_.price as price1_ from product
product0_ where product0_.price>(select AVG(product0_.price)
from product product0_)

Item Name:Mobile Price:8000.0

Item Name:T.V. Price:6000.0

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