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The internal connection pool has reached its maximum size and no connection is currently available!

 
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i was following a tutorial to practice hibernate. i'm facing the exception as below. Googled it but no convincing solution. any help ?



ERROR:

Exception in thread "main" 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$PooledConnections.poll(DriverManagerConnectionProviderImpl.java:290)
at org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl$PoolState.getConnection(DriverManagerConnectionProviderImpl.java:440)
at org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl.getConnection(DriverManagerConnectionProviderImpl.java:171)
at org.hibernate.internal.NonContextualJdbcConnectionAccess.obtainConnection(NonContextualJdbcConnectionAccess.java:38)
at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcIsolationDelegate.delegateWork(JdbcIsolationDelegate.java:48)
at org.hibernate.id.enhanced.TableStructure$1.getNextValue(TableStructure.java:125)
at org.hibernate.id.enhanced.NoopOptimizer.generate(NoopOptimizer.java:40)
at org.hibernate.id.enhanced.SequenceStyleGenerator.generate(SequenceStyleGenerator.java:523)
at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:115)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:194)
at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:38)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:179)
at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:32)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:75)
at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:102)
at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:636)
at org.hibernate.internal.SessionImpl.save(SessionImpl.java:629)
at org.hibernate.internal.SessionImpl.save(SessionImpl.java:624)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:567)
at org.hibernate.context.internal.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:351)
at com.sun.proxy.$Proxy30.save(Unknown Source)
at com.hibernateexample.HibernateDao.main(HibernateDao.java:19)



Hibernate config file:


Entity:


DAO class:



thanks in advance!!

 
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That's the kind of error you get when you have too many connections opened to the database. It generally means that you are not closing connections when you are done with them.

A Connection Pool is a collection of pre-allocated Connections. When you ask the pool for a Connection, it will take one of the Connections that it owns and give it to your application.

But you have to give the connection back when you're finished with it.

Otherwise the pool will run dry and this is what you end up with.
 
ssiva raman
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Tim Holloway wrote:That's the kind of error you get when you have too many connections opened to the database. It generally means that you are not closing connections when you are done with them.

A Connection Pool is a collection of pre-allocated Connections. When you ask the pool for a Connection, it will take one of the Connections that it owns and give it to your application.

But you have to give the connection back when you're finished with it.

Otherwise the pool will run dry and this is what you end up with.



Thank you for the reply , Tim.
If you have seen the code , you would find that i don't have too many connections to the DB and i close the session after each query.
Kindly , point out the mistake in the code.

Thanks again!!
 
ssiva raman
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The below configuration solved the problem. However , i want to know how the connection pool got exhausted when i've only one connection to the DB.
Any help is appreciated.

change:


Previous:
 
Tim Holloway
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A Hibernate session is not the same as a Connection. It uses Connections, but there's no direct 1-to-1 relation.

I think that the problem is that your open transaction is using one Connection, but when you do the "save", it also requires a Connection, making for 2 Connections but a pool size of only 1 Connection.

Just as a side note, I don't recommend using legacy Hibernate. It uses a proprietary ORM architecture. Hibernate JPA uses the JEE Standard ORM architecture and I suspect that eventually IBM will stop supporting legacy Hibernate in favor of Hibernate JPA. If Red Hat and IBM were Microsoft, they probably would have done so years ago.
 
ssiva raman
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Hi Tim,

Thank you for the clarification. could you suggest me a book i can read in more detail.?

thank you
 
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