Home Jpa Eclipsejpaexamples JPA Count Function
Questions:Ask|Latest


 
 

Share on Google+Share on Google+

JPA Count Function

Advertisement
In this section, you will learn about the count function of JPA aggregate function

JPA Count Function

     

In this section, you will learn about the count function of JPA aggregate function. JPA Count function counts all records to database table.

JPA Count Function:

Query query=em.createQuery("SELECT COUNT(p.itemName) FROM Product p");

This query gives total number of record to the database table. It returns a single numeric result.

Developing this application, you need the following artifacts:

  1. Database Table: product
  2. Model Class: Product.java
  3. Main Class: JPACountFunction.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: JPACountFunction.java

/**

*/
package roseindia;

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

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

/**
* @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 COUNT(p.itemName) FROM Product p");
Number countResult=(Number) query.getSingleResult();
System.out.println("Count result:"+countResult);
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 count(product0_.itemName) as col_0_0_ from product product0_

Count result:4

 

Advertisement

If you enjoyed this post then why not add us on Google+? Add us to your Circles



Liked it!  Share this Tutorial


Follow us on Twitter, or add us on Facebook or Google Plus to keep you updated with the recent trends of Java and other open source platforms.

Posted on: June 11, 2009

Ask Questions?    Discuss: JPA Count Function  

Post your Comment


Your Name (*) :
Your Email :
Subject (*):
Your Comment (*):
  Reload Image
 
 
Comments
DMCA.com