28 - Named Queries

We'll learn about named queries and how to write and access named queries. We'll also write and execute a NamedNativeQuery.

In general, you should prefer to write HQL queries because then you can let Hibernate handle the intricacies of converting the HQL into the various SQL dialects. This will make your job much simpler when you choose to switch DBMS providers.

@NamedQuery should be constructed with the query language (HQL or persistence query language).

@NamedNativeQuery should be constructed with native SQL.

Named Queries help to write query at Entity level using annotation @NamedQuery

@NamedQuery(name="UserDetails.byId", query="from UserDetails where userId = ?")

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.getNamedQuery("UserDetails.byId");

            //query.setInteger(0, 19);

           

            Query query = session.getNamedQuery("UserDetails.byName");

            query.setString(0, "User 9");

           

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

           

            session.getTransaction().commit();

            session.close();

           

            for(UserDetails u:users){

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

            }

           

      }

}

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.NamedNativeQuery;

import javax.persistence.NamedQuery;

import javax.persistence.OneToMany;

@Entity

@NamedQuery(name="UserDetails.byId", query="from UserDetails where userId = ?") //HQL query - based on class name

@NamedNativeQuery(name="UserDetails.byName", query="select * from UserDetails where username = ?", resultClass=UserDetails.class) //native query

@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"/>    

           

    </session-factory>

</hibernate-configuration>