Hibernate Interceptor Example

In order to use an Interceptor with our Session, we need to create a class that extends EmptyInterceptor.. Create a new class with name DataInterceptor.java. And now paste the following code:

package com.pkm.commands;

import java.io.Serializable;
import java.util.Iterator;
import org.hibernate.EmptyInterceptor;
import org.hibernate.Transaction;

public class DataInterceptor  extends EmptyInterceptor {
    private int updates = 0;
    private int creates = 0;
    private int loads = 0;
    private int deletes = 0;
    
    @Override
    public boolean onSave(Object entity, Serializable id, Object[] state, String[] propertyNames, org.hibernate.type.Type[] types) {
        System.out.println("onSave");
        creates++;
        return true;
    }
    
    // called on load events
    @Override
    public boolean onLoad(Object entity, Serializable id, Object[] state, String[] propertyNames, org.hibernate.type.Type[] types) {
        System.out.println("onLoad");
        loads++;
        return true;
    }

    @Override
    public boolean onFlushDirty(Object entity, Serializable id, Object[] currentState, Object[] previousState, String[] propertyNames, org.hibernate.type.Type[] types) {
        System.out.println("onFlushDirty");
        updates++;
        return false;
    }

    @Override
    public void onDelete(Object entity, Serializable id, Object[] state, String[] propertyNames, org.hibernate.type.Type[] types) {
        System.out.println("onDelete");
        deletes++;
    }

    //called before commit into database
    @Override
    public void preFlush(Iterator iterator) {
        System.out.println("preFlush");
    } 

    //called after committed into database
    @Override
    public void postFlush(Iterator iterator) {
        System.out.println("postFlush");
    }
    
    @Override
    public void afterTransactionCompletion(Transaction tx) {
        if ( tx.wasCommitted() ) {
            System.out.println("Creations: " + creates + ", Updates: " + 
                    updates + ", Loads: " + loads + ", Deletes: " + deletes);
        }
    }
}

These are the most basic methods that an Interceptor implements:

• onSave : Called when you save an object. The object is not persisted yet.
• onFlushDirty : Called when you update an object. The object is not persisted yet.
• onLoad: Called when you read an object from database.
• onDelete : Called when you delete an object. The object is not deleted from the database yet.
• preFlush : Called before committing to the database.
• postFlush :  Called after committing to the database.

We should also update HibernateUtil class:

package com.pkm.utils;

import com.pkm.commands.DataInterceptor;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistryBuilder;

public class HibernateUtil {
    private static final SessionFactory sessionFactory = buildSessionFactory();
    private static ServiceRegistry serviceRegistry;
    
    private static SessionFactory buildSessionFactory() {
        try {
            Configuration configuration = new Configuration().setInterceptor(new DataInterceptor());
            configuration.configure();
            serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry(); 
            return configuration.buildSessionFactory(serviceRegistry);
        } catch (Exception ex) {
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }
 
    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }

    public static void shutdown() {
        // Close caches and connection pools
        getSessionFactory().close();
    }
}

Now create main java class file to test the Interceptor.

package com.pkm.commands;

import com.pkm.domains.User;
import com.pkm.utils.HibernateUtil;
import org.hibernate.Session;
import org.hibernate.Transaction;

public class TestInterceptor {
    @SuppressWarnings("unchecked")
    public static void main(String[] args) {
        Session session = null;
     Transaction transaction = null;
        try {
            session = HibernateUtil.getSessionFactory().openSession();
            transaction = session.beginTransaction();

            User user = new User(System.currentTimeMillis() + "@gmail.com", "Pritom", "Kumar Mondal");
            session.save(user);
            Long firstId = user.getId();

            user = new User(System.currentTimeMillis() + "@gmail.com", "Pritom", "Kumar Mondal");
            session.save(user);
            Long secondId = user.getId();
            
            user = (User) session.get(User.class, firstId);
            user.setFirstName("First name changed");
            session.save(user);
            
            user = (User) session.get(User.class, secondId);
            session.delete(user);
            
            user = (User) session.get(User.class, Long.parseLong("10"));
            user = (User) session.get(User.class, Long.parseLong("11"));
            user = (User) session.get(User.class, Long.parseLong("12"));
            
            transaction.commit();
        } catch (Exception ex) {
            if(transaction != null) {
                transaction.rollback();
            }
            System.err.println(ex.getMessage());
        } finally {
            if(session != null) {
                session.close();
            }
        }
    }
}

Output of Example:

onSave
Hibernate: insert into User (email, first_name, last_name) values (?, ?, ?)
onSave
Hibernate: insert into User (email, first_name, last_name) values (?, ?, ?)
onDelete
Hibernate: select user0_.id as id0_0_, user0_.email as email0_0_, user0_.first_name as first3_0_0_, user0_.last_name as last4_0_0_ from User user0_ where user0_.id=?
onLoad
Hibernate: select user0_.id as id0_0_, user0_.email as email0_0_, user0_.first_name as first3_0_0_, user0_.last_name as last4_0_0_ from User user0_ where user0_.id=?
onLoad
Hibernate: select user0_.id as id0_0_, user0_.email as email0_0_, user0_.first_name as first3_0_0_, user0_.last_name as last4_0_0_ from User user0_ where user0_.id=?
onLoad
preFlush
onFlushDirty
Hibernate: update User set email=?, first_name=?, last_name=? where id=?
Hibernate: delete from User where id=?
postFlush
Creations: 2, Updates: 1, Loads: 3, Deletes: 1

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