Hibernate exception: The internal connection pool has reached its maximum size

Question

I am facing above issue, whenever I'm adding '@GeneratedValue' annotation to Id field. See below code snippet which I have used for saving entity using hibernate.

public class HibernateTest {
public static void main(String[] args) {
    Employee emp1 = new Employee();
    emp1.setName("User1");

    try (SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory(); Session session = sessionFactory.openSession()){
    session.beginTransaction();
    session.save(emp1);
    session.getTransaction().commit();
    } catch (Exception e) {
        e.printStackTrace();
    }

}

}

Below is my Entity class

@Entity
@Table (name = "Employee_Details")
public class Employee {
    @Id  @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;
    private String name;
    public int getId() { return id; }
    public void setId(int id) { this.id = id; } 
    public String getName() {
        return name;
    }
    public void setName(String name) { this.name = name; }
}

And in hibernate.cfg.xml, connection pool size is set to 1

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

I am closing the session as well as sessionFactory instance each time. Still facing below exception in logs

org.hibernate.HibernateException: The internal connection pool has reached its maximum size and no connection is currently available!
at org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl$PooledConnections.poll(DriverManagerConnectionProviderImpl.java:322)
at org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl.getConnection(DriverManagerConnectionProviderImpl.java:189)
at org.hibernate.internal.NonContextualJdbcConnectionAccess.obtainConnection(NonContextualJdbcConnectionAccess.java:35)
at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcIsolationDelegate.delegateWork(JdbcIsolationDelegate.java:48)
at org.hibernate.id.enhanced.TableStructure$1.getNextValue(TableStructure.java:125)
at org.hibernate.id.enhanced.NoopOptimizer.generate(NoopOptimizer.java:40)

If I remove 'GeneratedValue' annotation from Id field, this works fine. Can anyone tell me, why is this failing? And how to I resolve it?

RipperJugo · Accepted Answer · 2018-10-24 07:52:10Z

3

I had this problem and solved it by replacing:

@GeneratedValue(strategy = GenerationType.AUTO)

with:

@GeneratedValue(strategy = GenerationType.IDENTITY)

Hope it works for you too!

answered Oct 24, 2018 at 7:52

RipperJugo

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Comments

Kees Kuip · Accepted Answer · 2019-01-11 13:38:13Z

0

I think it uses a connection to determine the 'id'. Maybe setting the number of connections to 2 instead of 1 solves the problem.

answered Jan 11, 2019 at 13:38

Kees Kuip

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