Hibernate | Kode Java - Learn Java by Examples

How do I create a Criteria object?

By Wayan in Hibernate Last modified: May 21, 2023 0 Comment

This example show you how to create an instance of Hibernate Criteria class. To create a Criteria we call the factory method of the Session object and pass the persistence class as parameter. To execute the Criteria query we simply call the list() method.

package org.kodejava.hibernate;

import org.hibernate.SessionFactory;
import org.hibernate.Session;
import org.hibernate.HibernateException;
import org.hibernate.Criteria;
import org.hibernate.cfg.Configuration;
import org.kodejava.hibernate.model.Track;

import java.util.List;

public class CreateCriteriaDemo {
    public static Session getSession() throws HibernateException {
        String cfg = "hibernate.cfg.xml";
        SessionFactory sessionFactory = new Configuration().configure(cfg)
                .buildSessionFactory();
        return sessionFactory.openSession();
    }

    @SuppressWarnings("unchecked")
    public static void main(String[] args) {
        try (Session session = getSession()) {
            // Create a new Criteria to query for a collection of Tracks.
            // To create an instance of Criteria we call a createCriteria()
            // factory method of the Session object.
            Criteria criteria = session.createCriteria(Track.class);

            // Call the list() method to retrieve a collections of Tracks
            // from the database.
            List<Track> tracks = criteria.list();

            for (Track track : tracks) {
                System.out.println("Title     = " + track.getTitle());
                System.out.println("Artist    = " + track.getArtist().getName());
                System.out.println("Genre     = " + track.getGenre().getName());
                System.out.println("Record    = " + track.getRecord().getTitle());
                System.out.println("Label     = " + track.getRecord().getLabel().getName());
                System.out.println("-----------------------------------");
            }
        }
    }
}

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>5.6.9.Final</version>
    </dependency>
    <dependency>
        <groupId>com.mysql</groupId>
        <artifactId>mysql-connector-j</artifactId>
        <version>8.0.33</version>
    </dependency>
</dependencies>

How do I limit Hibernate query result?

By Wayan in Hibernate Last modified: May 21, 2023 0 Comment

In the example below you’ll see how to limit the number of records returned by hibernate queries. Limiting the query result is usually use for creating pagination, where we can navigate from page to page of data in our application but only a few of them are read from the database.

In hibernate Query object we need to specify the first result and max results by calling the setFirstResult() and setMaxResults() methods to limit the query results.

package org.kodejava.hibernate.service;

import org.hibernate.Session;
import org.hibernate.query.Query;
import org.kodejava.hibernate.SessionFactoryHelper;
import org.kodejava.hibernate.model.Label;

import java.util.List;

public class LabelService {
    public List<Label> getLabels(int pageNumber, int pageSize) {
        Session session =
                SessionFactoryHelper.getSessionFactory().getCurrentSession();
        session.beginTransaction();

        Query<Label> query = session.createQuery("from Label", Label.class);

        // Set the first record position and the max number of record to be
        // read. The setFirstResult() tell hibernate from which row the data
        // should be read. In the example if we have pages of 10 records,
        // passing the page number 2 will read 10 records from the 20th row
        // in the selected records.
        query.setFirstResult((pageNumber - 1) * pageSize);
        query.setMaxResults(pageSize);

        List<Label> labels = query.list();
        session.getTransaction().commit();
        return labels;
    }
}

package org.kodejava.hibernate;

import org.kodejava.hibernate.model.Label;
import org.kodejava.hibernate.service.LabelService;

import java.util.List;

public class LimitDemo {
    public static void main(String[] args) {
        LabelService service = new LabelService();

        List<Label> labels = service.getLabels(1, 10);
        for (Label label : labels) {
            System.out.println("Label = " + label);
        }
    }
}

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>5.6.9.Final</version>
    </dependency>
    <dependency>
        <groupId>com.mysql</groupId>
        <artifactId>mysql-connector-j</artifactId>
        <version>8.0.33</version>
    </dependency>
</dependencies>

How do I retrieve a list of Hibernate’s persistent objects?

By Wayan in Hibernate Last modified: May 21, 2023 0 Comment

In this example we add the function to read a list of records in our LabelService class. This function will read all Label persistent object from database. You can see the other functions such as saveLabel, getLabel and deleteLabel in the related example section of this example.

package org.kodejava.hibernate.service;

import org.hibernate.Session;
import org.kodejava.hibernate.SessionFactoryHelper;
import org.kodejava.hibernate.model.Label;

import java.util.List;

public class LabelService {
    public List<Label> getLabels() {
        Session session =
                SessionFactoryHelper.getSessionFactory().getCurrentSession();
        session.beginTransaction();

        // We read labels record from database using a simple Hibernate
        // query, Hibernate Query Language (HQL).
        List<Label> labels = session.createQuery("from Label", Label.class)
                .list();
        session.getTransaction().commit();

        return labels;
    }

    public void saveLabel(Label label) {
        // To save an object we first get a session by calling 
        // getCurrentSession() method from the SessionFactoryHelper class. 
        // Next we create a new transaction, save the Label object and 
        // commit it to database,
        Session session = SessionFactoryHelper.getSessionFactory()
                .getCurrentSession();

        session.beginTransaction();
        session.save(label);
        session.getTransaction().commit();
    }
}

package org.kodejava.hibernate;

import org.kodejava.hibernate.model.Label;
import org.kodejava.hibernate.service.LabelService;

import java.util.Date;
import java.util.List;

public class ListDemo {
    public static void main(String[] args) {
        LabelService service = new LabelService();

        // Creates a Label object we are going to store in the database.
        // We set the name, modified by and modified date information.
        Label newLabel = new Label();
        newLabel.setName("PolyGram");
        newLabel.setCreated(new Date());

        // Call the LabelManager saveLabel method.
        service.saveLabel(newLabel);

        List<Label> labels = service.getLabels();
        for (Label label : labels) {
            System.out.println("Label = " + label);
        }
    }
}

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>5.6.9.Final</version>
    </dependency>
    <dependency>
        <groupId>com.mysql</groupId>
        <artifactId>mysql-connector-j</artifactId>
        <version>8.0.33</version>
    </dependency>
</dependencies>

How do I delete persistent object in Hibernate?

By Wayan in Hibernate Last modified: May 21, 2023 0 Comment

Continuing the previous example How do I get object from database in Hibernate?, we now add the delete function in our LabelService class.

package org.kodejava.hibernate.service;

import org.hibernate.Session;
import org.kodejava.hibernate.SessionFactoryHelper;
import org.kodejava.hibernate.model.Label;

public class LabelService {
    public Label getLabel(Long id) {
        Session session =
                SessionFactoryHelper.getSessionFactory().getCurrentSession();
        session.beginTransaction();

        // We get back Label object from database by calling the Session
        // object get() method and passing the object type and the object
        // id to be read.
        Label label = session.get(Label.class, id);
        session.getTransaction().commit();

        return label;
    }

    public void deleteLabel(Long id) {
        // Load the object to be deleted
        Label label = getLabel(id);

        // We get the current session and delete the Label object from 
        // database.
        Session session =
                SessionFactoryHelper.getSessionFactory().getCurrentSession();
        session.beginTransaction();
        session.delete(label);
        session.getTransaction().commit();
    }
}

package org.kodejava.hibernate;

import org.kodejava.hibernate.model.Label;
import org.kodejava.hibernate.service.LabelService;

import java.util.Date;

public class DeleteDemo {
    public static void main(String[] args) {
        LabelService service = new LabelService();

        // Creates a Label object we are going to store in the database.
        // We set the name and created date information.
        Label label = new Label();
        label.setName("Sony Music");
        label.setCreated(new Date());

        // Call the LabelManager saveLabel method.
        service.saveLabel(label);

        // Read the object back from database.
        label = service.getLabel(label.getId());
        System.out.println("Label = " + label);

        service.deleteLabel(label.getId());
    }
}

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>5.6.9.Final</version>
    </dependency>
    <dependency>
        <groupId>com.mysql</groupId>
        <artifactId>mysql-connector-j</artifactId>
        <version>8.0.33</version>
    </dependency>
</dependencies>

How do I retrieve object from database in Hibernate?

By Wayan in Hibernate Last modified: May 21, 2023

In the How do I store object in Hibernate? example you’ll see how tho store objects into database. In this example we’ll extend the LabelService class and add the capability to get or query object from database.

package org.kodejava.hibernate.service;

import org.hibernate.Session;
import org.kodejava.hibernate.SessionFactoryHelper;
import org.kodejava.hibernate.model.Label;

public class LabelService {
    public Label getLabel(Long id) {
        Session session =
                SessionFactoryHelper.getSessionFactory().getCurrentSession();
        session.beginTransaction();

        // We get back Label object from database by calling the Session
        // object get() method and passing the object type and the object
        // id to be read.
        Label label = session.get(Label.class, id);
        session.getTransaction().commit();

        return label;
    }
}

package org.kodejava.hibernate;

import org.kodejava.hibernate.model.Label;
import org.kodejava.hibernate.service.LabelService;

public class LoadDemo {
    public static void main(String[] args) {
        // Create an instance of LabelService.
        LabelService service = new LabelService();

        // We call the getLabel() method and pass the label id to load it
        // from the database and print out the label string.
        Label label = service.getLabel(1L);
        System.out.println("label = " + label);
    }
}

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>5.6.9.Final</version>
    </dependency>
    <dependency>
        <groupId>com.mysql</groupId>
        <artifactId>mysql-connector-j</artifactId>
        <version>8.0.33</version>
    </dependency>
</dependencies>