package org.hibernate.bugs;

import java.util.Date;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

@Entity
public class Event {

    @Id
    @GeneratedValue
    private Long id;

    @Temporal(TemporalType.TIMESTAMP )
    private Date createdOn;

    public Event() {
    }

    public Event(Date createdOn) {
        this.createdOn = createdOn;
    }

    public Long getId() {
        return id;
    }

    public Date getCreatedOn() {
        return createdOn;
    }
}

package org.hibernate.bugs;

import static org.junit.Assert.assertEquals;

import java.lang.reflect.Field;
import java.util.Date;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.engine.query.spi.QueryPlanCache;
import org.hibernate.internal.SessionFactoryImpl;
import org.hibernate.internal.util.collections.BoundedConcurrentHashMap;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

/**
 * This template demonstrates how to develop a test case for Hibernate ORM, using the Java Persistence API.
 */
public class JPAUnitTestCase {

	private EntityManagerFactory entityManagerFactory;

	@Before
	public void init() {
		entityManagerFactory = Persistence.createEntityManagerFactory( "templatePU" );
	}

	@After
	public void destroy() {
		entityManagerFactory.close();
	}

	// Entities are auto-discovered, so just add them anywhere on class-path
	// Add your tests, using standard JUnit.
	@Test
	public void hhh123Test() throws Exception {
		EntityManager entityManager = entityManagerFactory.createEntityManager();
		entityManager.getTransaction().begin();
		
		Session session = entityManager.unwrap(Session.class);
		SessionFactory sessionFactory = session.getSessionFactory();
		SessionFactoryImpl factoryImpl = (SessionFactoryImpl) sessionFactory;
		QueryPlanCache cache = factoryImpl.getQueryPlanCache();
		Field f = cache.getClass().getDeclaredField("queryPlanCache");
		f.setAccessible(true);
		BoundedConcurrentHashMap queryPlanCache = (BoundedConcurrentHashMap) f.get(cache);
		assertEquals(0, queryPlanCache.size());
		
	    
		Event event = new Event( new Date() );
		entityManager.persist( event );
	    
		System.out.println(Runtime.getRuntime().totalMemory());
		
	    for (int i = 0; i < 10000; i++) {

	    	assertEquals(0, queryPlanCache.size());

		    Event dbEvent = entityManager.createQuery("select e from Event e", Event.class).getSingleResult();
		    
		    assertEquals(event.getCreatedOn(), dbEvent.getCreatedOn());
		    assertEquals(1, queryPlanCache.size());
		    
		    queryPlanCache.clear();
		    
		    assertEquals(0, queryPlanCache.size());
			
		    if(i%100 == 0) {
		    	System.gc();
		    	System.out.println(String.format("i: %d, percentage mem: %f", i, (Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory()) * 100.0/Runtime.getRuntime().totalMemory() ));
		    }
		}
	    
		entityManager.getTransaction().commit();
		entityManager.close();
	}
}