Hibernate Session createCriteria(), contains() and cancelQuery() Example
December 01, 2015
Sample Data Used in Demo
Session createCriteria()
Session.createCriteria() accepts entity name and returns the instance of org.hibernate.Criteria to which we can add restriction using Restrictions class of hibernate while fetching data. We use createCriteria() as follows.
List<?> std = session.createCriteria(Student.class).
add(Restrictions.le("id", 2)).addOrder(Order.asc("name")).list();
CreateCriteriaDemo.java
package com.concretepage;
import java.util.List;
import org.hibernate.Session;
import org.hibernate.criterion.Order;
import org.hibernate.criterion.Restrictions;
public class CreateCriteriaDemo {
public static void main(String[] args) {
Session session = HibernateUtil.getSessionFactory().openSession();
List<?> std = session.createCriteria(Student.class).
add(Restrictions.le("id", 2)).addOrder(Order.asc("name")).list();
for(int i = 0; i<std.size(); i++) {
Student s = (Student)std.get(i);
System.out.println(s.getId()+", "+ s.getName());
}
session.close();
}
}
Hibernate: select this_.id as id1_0_0_, this_.name as name2_0_0_ from student this_ where this_.id<=? order by this_.name asc 1, AA 2, BB
Session contains()
Session.contains() checks if the session contains the given instance. We need to pass instance to this method as an argument. We use it as follows.
session.contains(std));
Session.contains() will return false and in case of persistent state, it returns true. Now find the example for Session.contains().
ContainsDemo.java
package com.concretepage;
import org.hibernate.Session;
public class ContainsDemo {
Session session = HibernateUtil.getSessionFactory().openSession();
public static void main(String[] args) {
Session session = HibernateUtil.getSessionFactory().openSession();
//session.contains() returns true for persistent instance.
Student std = (Student)session.get(Student.class, 1);
System.out.println(session.contains(std));
//session.contains() returns false for detached instance.
session.evict(std);
System.out.println(session.contains(std));
//session.contains() returns false for transient object.
Student s = new Student();
s.setId(1);
s.setName("AA");
System.out.println(session.contains(s));
}
}
Hibernate: select student0_.id as id1_0_0_, student0_.name as name2_0_0_ from student student0_ where student0_.id=? true false false
Session cancelQuery()
Session.cancelQuery() is used to cancel the execution of query. We can call this method from another thread safely. We use this method as follows.
session.cancelQuery();
CancelQueryDemo.java
package com.concretepage;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import org.hibernate.Query;
import org.hibernate.Session;
public class CancelQueryDemo {
Session session = HibernateUtil.getSessionFactory().openSession();
public static void main(String[] args) {
ExecutorService exService = Executors.newFixedThreadPool(2);
CancelQueryDemo ob = new CancelQueryDemo();
exService.execute(ob.new ThreadOne());
exService.execute(ob.new ThreadTwo());
}
class ThreadOne implements Runnable {
@Override
public void run() {
List<?> std = session.createQuery("FROM Student").list();
for(int i = 0; i<std.size(); i++) {
Student s = (Student)std.get(i);
System.out.println(s.getId()+", "+ s.getName());
}
}
}
class ThreadTwo implements Runnable {
@Override
public void run() {
session.cancelQuery();
}
}
protected void finilize() {
session.close();
}
}
Hibernate Utility and Entity class
Find the Hibernate Utility class.HibernateUtil.java
package com.concretepage;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
private static SessionFactory sessionFactory ;
static {
Configuration configuration = new Configuration().configure();
StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder()
.applySettings(configuration.getProperties());
sessionFactory = configuration.buildSessionFactory(builder.build());
}
public static SessionFactory getSessionFactory() {
return sessionFactory;
}
}
Student.java
package com.concretepage;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name="student")
public class Student {
@Id
@Column(name="id")
private int id;
@Column(name="name")
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
