26 - Select-and-Pagination-in-HQL

HibernateTest.java

package org.yash.hibernate;

import java.util.List;

import org.hibernate.Query;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

import org.yash.dto.UserDetails;

public class HibernateTest {

      public static void main(String args[]) {

           

            SessionFactory sessionFactory = new Configuration().configure()

                        .buildSessionFactory();

            Session session = sessionFactory.openSession();

            session.beginTransaction();

            //Query query = session.createQuery("from UserDetails");

            Query query = session.createQuery("select userName from UserDetails");

            //Query query = session.createQuery("select new map(userid, userName) from UserDetails");

           

            //pagination

            query.setFirstResult(2); //Start point

            query.setMaxResults(4); //end point

           

            //List<UserDetails> users = (List<UserDetails>)query.list();

            List<String> users = (List<String>)query.list();

           

           

            session.getTransaction().commit();

            session.close();

           

/*          for(UserDetails u:users){

                  System.out.println(u.getUserName());

            }*/

           

            for(String u:users){

                  System.out.println(u);

            }

      }

}

UserDetails.java

package org.yash.dto;

import java.util.ArrayList;

import java.util.Collection;

import javax.persistence.CascadeType;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.GenerationType;

import javax.persistence.Id;

import javax.persistence.OneToMany;

@Entity

@org.hibernate.annotations.Entity(selectBeforeUpdate=true)

public class UserDetails {

      /* @Id says "userId" is primary key */

      @Id @GeneratedValue (strategy=GenerationType.AUTO)

      private int userId;    

      private String userName;

      @OneToMany(cascade=CascadeType.PERSIST)

      private Collection<Vehicle> vehicle = new ArrayList<Vehicle>();

           

      public int getUserId() {

            return userId;

      }

      public void setUserId(int userId) {

            this.userId = userId;

      }

      public String getUserName() {

            return userName;

      }

      public void setUserName(String userName) {

            this.userName = userName;

      }

      public void setVehicle(Collection<Vehicle> vehicle) {

            this.vehicle = vehicle;

      }

      public Collection<Vehicle> getVehicle() {

            return vehicle;

      }

}

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>

<!DOCTYPE hibernate-configuration PUBLIC

        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"

        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>

        <property name="connection.driver_class">

            org.postgresql.Driver

        </property>

        <property name="connection.url">

            jdbc:postgresql://localhost:5433/hibernatedb

        </property>

        <property name="connection.username">postgres</property>

        <property name="connection.password">admin</property>

        <!-- JDBC connection pool (use the built-in) -->

        <property name="connection.pool_size">1</property>

        <!-- SQL dialect -->

        <property name="dialect">

            org.hibernate.dialect.PostgreSQLDialect

        </property>

        <!-- Enable Hibernate's automatic session context management -->

        <property name="current_session_context_class">thread</property>

       

        <!-- Echo all executed SQL to stdout -->

        <property name="show_sql">true</property>

       

        <!-- Drop and re-create the database schema on startup -->

            <property name="hbm2ddl.auto">update</property>  

            <!-- create / update -->

   

          <!-- Names the annotated entity class -->

            <mapping class="org.yash.dto.UserDetails"/>    

            <mapping class="org.yash.dto.Vehicle"/>  

            <mapping class="org.yash.dto.TwoWheeler"/>     

            <mapping class="org.yash.dto.FourWheeler"/>    

           

    </session-factory>

</hibernate-configuration>