Java / Hibernate - Exception: The internal connection pool has reached its maximum size and there is currently no connection

Question

I'm using Hibernate for the first time for a university project, and I'm a little newbie. I think I followed all the instructions given by my professor and some textbooks that I read, but I continue to receive the Exception, which is in the title:

Exception in thread "main" org.hibernate.HibernateException: The internal connection pool has reached its maximum size and no connection is currently available! 

What I'm trying to do is just save the object ( AbitazioneDB ) in the MySql database that I already created. This is my configuration file:

 <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <!-- Connection to the database --> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://localhost:3306/AllarmiDomesticiDB</property> <!-- Credentials --> <property name="hibernate.connection.username">root</property> <property name="connection.password">password</property> <!-- JDBC connection pool (use the built-in) --> <property name="connection.pool_size">1</property> <!-- SQL dialect --> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <!-- Enable Hibernate automatic session context management --> <property name="current_session_context_class">thread</property> <!-- Disable the second-level cache --> <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property> <property name="show_sql">true</property> <!-- Entity --> <mapping class="it.allarmiDomestici.centraleOperativaRemota.dbWrapper.AbitazioneDB" /> </session-factory> </hibernate-configuration> 

This is my AbitazioneDB class (I will omit getters and setters):

 @Entity @Table(name="abitazioni") public class AbitazioneDB { @Id @GeneratedValue @Column(name="id") private Integer id; @Column(name="indirizzo") private String indirizzo; @Column(name="nome_proprietario") private String nomeProprietario; @Column(name="tel_proprietario") private String telProprietario; public AbitazioneDB(){ super(); } public AbitazioneDB save(){ SessionFactory sf = HibernateUtil.getSessionFactory(); Session session = sf.getCurrentSession(); session.beginTransaction(); Integer id = (Integer) session.save(this); this.setId(id); session.getTransaction().commit(); session.close(); return this; } } 

This is my HibernateUtil class:

 public class HibernateUtil { private static SessionFactory sessionFactory; private static SessionFactory createSessionFactory() { sessionFactory = new Configuration().configure().buildSessionFactory(); return sessionFactory; } public static SessionFactory getSessionFactory() { if (sessionFactory == null) sessionFactory = createSessionFactory(); return sessionFactory; } } 

And this is my TestHibernate class using the main method:

 public class TestHibernate { public static void main(String[] args) { AbitazioneDB ab = new AbitazioneDB(); ab.setIndirizzo("Via Napoli, 29"); ab.setNomeProprietario("Mario Rossi"); ab.setTelProprietario("3333333333"); ab.save(); System.out.println("Ok!"); } } 

When I run TestHibernate , I always get this exception, and I have no idea why. Maybe I should change the connection.pool_size property, but if I do, it seems like I'm getting more errors. Can anybody help me?

Answer 1

Try the following:

HibernateUtil:

 public static Session getHibernateSession() { final SessionFactory sf = new Configuration() .configure("yourConfig.cfg.xml").buildSessionFactory(); // factory = new Configuration().configure().buildSessionFactory(); final Session session = sf.openSession(); return session; } 

And instead of using SessionFactory use Session:

 final Session session = HibernateUtil.getHibernateSession(); 

And then use:

  Transaction tx = session.beginTransaction(); // all your methods tx.commit(); session.close(); 

Hope this helps.

And you really cannot have this connection pool property in your hbm unless you need it.

Answer 2

Your connection pool has run out of connections because you are using one connection in the pool.

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

Change this property to your convenience, for example 100

Answer 3

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

Try changing the size of the connection pool to a larger size, for example, about 100.

 <property name="connection.pool_size">100</property>