In the previous section, we fetched single column only. Now, we will learn how to handle bulk data and perform corresponding operations.
JPQL Bulk Data Example
In this example, we will take a basic entity class (in this case StudentEntity.java) and perform different operations on it.
Step 1. Create an entity class named as StudentEntity.java under com.javahubpoint.jpa package.
StudentEntity.java
import javax.persistence.*;
@Entity
@Table(name="student")
public class StudentEntity {
@Id
private int s_id;
private String s_name;
private int s_age;
public StudentEntity(int s_id, String s_name, int s_age) {
super();
this.s_id = s_id;
this.s_name = s_name;
this.s_age = s_age;
}
public StudentEntity() {
super();
}
public int getS_id() {
return s_id;
}
public void setS_id(int s_id) {
this.s_id = s_id;
}
public String getS_name() {
return s_name;
}
public void setS_name(String s_name) {
this.s_name = s_name;
}
public int getS_age() {
return s_age;
}
public void setS_age(int s_age) {
this.s_age = s_age;
}
}
Step 2. Now, map the entity class and other databases configuration in Persistence.xml file.
Persistence.xml
<persistence-unit name="Student_details">
<class>com.javahubpoint.jpa.StudentEntity</class>
<properties>
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/studentdata"/>
<property name="javax.persistence.jdbc.user" value="root"/>
<property name="javax.persistence.jdbc.password" value=""/>
<property name="eclipselink.logging.level" value="SEVERE"/>
<property name="eclipselink.ddl-generation" value="create-or-extend-tables"/>
</properties>
</persistence-unit>
</persistence>
Step 3. Now, we can perform any of the following operations on StudentEntity.java class.
1. JPQL Fetch
Here, we will fetch all the records from the database.
FetchData.java
import com.javahubpoint.jpa.StudentEntity;
import javax.persistence.*;
import java.util.*;
public class FetchData {
public static void main( String args[]) {
EntityManagerFactory emf = Persistence.createEntityManagerFactory( "Student_details" );
EntityManager em = emf.createEntityManager();
em.getTransaction().begin( );
Query query = em.createQuery( "Select s from StudentEntity s ");
@SuppressWarnings("unchecked")
List<StudentEntity> list=(List<StudentEntity>)query.getResultList( );
System.out.print("s_id");
System.out.print("\t s_name");
System.out.println("\t s_age");
for( StudentEntity s:list ){
System.out.print( s.getS_id( ));
System.out.print("\t" + s.getS_name( ));
System.out.print("\t" + s.getS_age( ));
System.out.println();
}
em.getTransaction().commit();
em.close();
emf.close();
}
}
Output:
2. JPQL Update
Here, we will update the records in database.
UpdateData.java
import javax.persistence.*;
public class UpdataData {
public static void main( String args[]) {
EntityManagerFactory emf = Persistence.createEntityManagerFactory( "Student_details" );
EntityManager em = emf.createEntityManager();
em.getTransaction().begin( );
Query query = em.createQuery( "update StudentEntity SET s_age=25 where s_id>103");
query.executeUpdate();
em.getTransaction().commit();
em.close();
emf.close();
}
}
Output:
After the execution of the program, the following student table generates under MySQL workbench. To fetch data, run select * from student in MySQL.
3. JPQL Delete
Here, we will delete the particular records from database.
DeleteData.java
import javax.persistence.*;
public class DeleteData {
public static void main( String args[]) {
EntityManagerFactory emf = Persistence.createEntityManagerFactory( "Student_details" );
EntityManager em = emf.createEntityManager();
em.getTransaction().begin( );
Query query = em.createQuery( "delete from StudentEntity where s_id=102");
query.executeUpdate();
em.getTransaction().commit();
em.close();
emf.close();
}
}
Output:
After the execution of the program, the following student table generates under MySQL workbench. To fetch data, run select * from student in MySQL.
