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JPA-QL Queries

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In this section, we will use the simple JPA-QL query in our JPA application. Here JPA-QL query used with createQuery() method of EntityManager.

JPA-QL Queries

     

In this section, we will use the simple JPA-QL query in our JPA application. Here JPA-QL query used with createQuery() method of EntityManager

Steps to create the example code:

  1. Database Table: student
  2. Model Class: Student.java
  3. Main Class: JPAQL.java

Database Table: student

CREATE TABLE `student` ( 
`id` int(11) NOT NULL auto_increment, 
`sname` varchar(100) NOT NULL, 
`sroll` int(11) NOT NULL, 
`scourse` varchar(10) NOT NULL, 
PRIMARY KEY (`id`) 
)

Model Class: Student.java

/**

*/
package roseindia;

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

/**
* @author Administrator
*
*/
@Entity
@Table(name="student")

public class Student {

@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="sname", length=100,nullable=false)
private String sname;

/**
* @return the sname
*/
public String getSname() {
return sname;
}

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

@Column(name="sroll",nullable=false)
private int sroll;

/**
* @return the sroll
*/
public int getSroll() {
return sroll;
}

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

@Column(name="scourse",length=10,nullable=false)
private String scourse;

/**
* @return the scourse
*/
public String getScourse() {
return scourse;
}

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

}

Main Class: JPAQL.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 JPAQL {

/**
* @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 q = em.createQuery("SELECT st FROM Student st WHERE st.sname LIKE :stuName");
q.setParameter("stuName", "vinod");
List result = q.getResultList();
if(result.size()!=0){
Iterator stIterator=result.iterator();
while(stIterator.hasNext()){
Student st=(Student)stIterator.next();
System.out.print("sname:"+st.getSname());
System.out.print(" sroll:"+st.getSroll());
System.out.print(" scourse:"+st.getScourse());
System.out.println();
}
}
else{
System.out.println("Record not found.");
}
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 student0_.id as id0_, student0_.scourse as
scourse0_, student0_.sname as sname0_, student0_.sroll as
sroll0_ from student student0_ where student0_.sname like ?

sname:Vinod sroll:101 scourse:MCA

 

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Posted on: September 27, 2006

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Comments
sunil kumar
July 11, 2011
Question

what is the function of these statements?? EntityManagerFactory emf=Persistence.createEntityManagerFactory("jpa"); EntityManager em=emf.createEntityManager();
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