HowToDoInJava

Hibernate C3P0 Connection Pool Configuration Tutorial

By | Filed Under: Hibernate

By default, Hibernate uses JDBC connections in order to interact with a database. Creating these connections is expensive—probably the most expensive single operation Hibernate will execute in a typical-use case. Since JDBC connection management is so expensive that possibly you will advise to use a pool of connections, which can open connections ahead of time (and close them only when needed, as opposed to “when they’re no longer used”).

Thankfully, Hibernate is designed to use a connection pool by default, an internal implementation. However, Hibernate’s built-in connection pooling isn’t designed for production use. In production, you would use an external connection pool by using either a database connection provided by JNDI or an external connection pool configured via parameters and classpath.

C3P0  is an example of an external connection pool. In this tutorial, we will learn to use it with hibernate.

Table of Contents

1) Maven dependencies
2) Configure C3P0 Connection Pool with Hibernate 
3) Test connection pooling in runtime

1) Maven dependencies

To configure c3p0 with hibernate, we need to add c3p0 and Hibernate’s c3p0 connection provider as dependencies in the pom.xml. Please note that the version of the hibernate-c3p0 dependency should match the Hibernate’s compatible version.

Below configuration uses the latest versions of both i.e. hibernate as well as c3p0.

<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-c3p0</artifactId>
    <version>4.3.6.Final</version>
</dependency>
<dependency>
	<groupId>c3p0</groupId>
	<artifactId>c3p0</artifactId>
	<version>0.9.1.2</version>
</dependency>

2) Configure C3P0 Connection Pool with Hibernate

The best part is that the configuration of C3P0 with hibernate is really very easy. Just add any c3p0 property inside your hibernate.cfg.xml file and that’s it. e.g. add the following entry in hibernate.cfg.xml.

<property name="hibernate.c3p0.min_size">10</property>

Congratulations !! Connection pooling with C3P0 is now configured with your application’s hibernate layer. You are good to start testing the things. Really easy, Isn’t it?

A rather detailed configuration can be setup using following properties in hibernate.cfg.xml.

<property name="hibernate.c3p0.min_size">10</property>
<property name="hibernate.c3p0.max_size">20</property>
<property name="hibernate.c3p0.acquire_increment">1</property>
<property name="hibernate.c3p0.idle_test_period">3000</property>
<property name="hibernate.c3p0.max_statements">50</property>
<property name="hibernate.c3p0.timeout">1800</property>

You can find detailed information about about above configuration switches in official documentation.

3) Test connection pooling in runtime

Without C3P0 Connection Pool Configuration

Without C3P0 configured, if you see the debug logs of hibernate, you will see something like this:

DEBUG Configuration:1841 - Preparing to build session factory with filters : {}
WARN DriverManagerConnectionProviderImpl:93 - HHH000402: Using Hibernate built-in connection pool (not for production use!)
INFO DriverManagerConnectionProviderImpl:166 - HHH000401: using driver [org.hsqldb.jdbcDriver] at URL [jdbc:hsqldb:mem:howtodoinjava]
INFO DriverManagerConnectionProviderImpl:172 - HHH000046: Connection properties: {user=sa, password=}
INFO DriverManagerConnectionProviderImpl:180 - HHH000006: Autocommit mode: false
INFO DriverManagerConnectionProviderImpl:102 - HHH000115: Hibernate connection pool size: 20 (min=1)
DEBUG DriverManagerConnectionProviderImpl:104 - Initializing Connection pool with 1 Connections
...
...
...
EBUG JdbcTransaction:113 - committed JDBC Connection
DEBUG SessionFactoryImpl:1339 - HHH000031: Closing
DEBUG AbstractServiceRegistryImpl:406 - Implicitly destroying ServiceRegistry on de-registration of all child ServiceRegistries
INFO DriverManagerConnectionProviderImpl:281 - HHH000030: Cleaning up connection pool [jdbc:hsqldb:mem:howtodoinjava]

Using C3P0 Connection Pool Configuration

After configuring C3P0 Connection Pool, you will be able to see in the logs that connections are now acquired from C3P0 Connection Pool itself.

DEBUG Configuration:1841 - Preparing to build session factory with filters : {}
 INFO C3P0ConnectionProvider:133 - HHH010002: C3P0 using driver: org.hsqldb.jdbcDriver at URL: jdbc:hsqldb:mem:howtodoinjava
 INFO C3P0ConnectionProvider:134 - HHH000046: Connection properties: {user=sa, password=****}
 INFO C3P0ConnectionProvider:137 - HHH000006: Autocommit mode: false
 INFO MLog:92 - MLog clients using log4j logging.
 INFO C3P0Registry:216 - Initializing c3p0-0.9.2.1 [built 20-March-2013 10:47:27 +0000; debug? true; trace: 10]
DEBUG DynamicPooledDataSourceManagerMBean:258 - MBean: com.mchange.v2.c3p0:type=PooledDataSource,identityToken=19tu9of94ho8s13xij3fm|34e475e1,name=19tu9of94ho8s13xij3fm|34e475e1 registered.
DEBUG DynamicPooledDataSourceManagerMBean:253 - MBean: com.mchange.v2.c3p0:type=PooledDataSource,identityToken=19tu9of94ho8s13xij3fm|34e475e1,name=19tu9of94ho8s13xij3fm|34e475e1 unregistered, in order to be reregistered after update.
DEBUG DynamicPooledDataSourceManagerMBean:258 - MBean: com.mchange.v2.c3p0:type=PooledDataSource,identityToken=19tu9of94ho8s13xij3fm|34e475e1,name=19tu9of94ho8s13xij3fm|34e475e1 registered.
 INFO AbstractPoolBackedDataSource:522 - Initializing c3p0 pool... com.mchange.v2.c3p0.PoolBackedDataSource@d29bbf50 [ connectionPoolDataSource -> com.mchange.v2.c3p0.WrapperConnectionPoolDataSource@a9bbd924 [ ... ]
 ...
 ...
 ...
 DEBUG ActiveManagementCoordinator:97 - C3P0Registry mbean unregistered.
DEBUG BasicResourcePool:1022 - Preparing to destroy resource: com.mchange.v2.c3p0.impl.NewPooledConnection@1d1fcfbb
DEBUG C3P0PooledConnectionPool:616 - Preparing to destroy PooledConnection: com.mchange.v2.c3p0.impl.NewPooledConnection@1d1fcfbb
DEBUG AbstractPoolBackedDataSource:477 - com.mchange.v2.c3p0.PoolBackedDataSource@34e475e1 has been closed. 
java.lang.Exception: DEBUG STACK TRACE for PoolBackedDataSource.close().
	at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.close(AbstractPoolBackedDataSource.java:477)
	at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.close(AbstractPoolBackedDataSource.java:489)
	at com.mchange.v2.c3p0.DataSources.destroy(DataSources.java:372)
	at com.mchange.v2.c3p0.DataSources.destroy(DataSources.java:348)
	at org.hibernate.c3p0.internal.C3P0ConnectionProvider.stop(C3P0ConnectionProvider.java:258)
	at org.hibernate.service.internal.AbstractServiceRegistryImpl.stopService(AbstractServiceRegistryImpl.java:377)
	at org.hibernate.service.internal.AbstractServiceRegistryImpl.destroy(AbstractServiceRegistryImpl.java:361)
	at org.hibernate.service.internal.AbstractServiceRegistryImpl.deRegisterChild(AbstractServiceRegistryImpl.java:410)
	at org.hibernate.service.internal.AbstractServiceRegistryImpl.destroy(AbstractServiceRegistryImpl.java:368)
	at org.hibernate.internal.SessionFactoryImpl.close(SessionFactoryImpl.java:1377)
	at com.howtodoinjava.demo.util.HibernateUtil.shutdown(HibernateUtil.java:39)
	at com.howtodoinjava.test.TestHibernate.main(TestHibernate.java:22)

That’s all for this easy but useful tutorial about configuring C3P0 Connection Pool with hibernate.

Happy Learning !!

Reference: http://www.mchange.com/projects/c3p0/#configuration

Feedback, Discussion and Comments

  1. I could resolve this by going over multiple site and finding a similar issue.
    Problem what I was not doing is handling transactions even for select queries. Due to which I see connection in “idle with transaction” state, which means the connection is not getting released. Once I handled the begin commit rollback properly, it goes fine.
    Thanks for your support.
    Hibernate-cfg.xml for reference:

    org.postgresql.Driver
    org.hibernate.dialect.PostgreSQLDialect
    jdbc:postgresql://localhost:5432/kairos
    postgres
    compitoplus
    <!–
    20/>
    –>
    50

    false
    <!– true –>
    validate


    org.hibernate.connection.C3P0ConnectionProvider
    5
    20
    300
    50
    3000
    true
    100
    <!– org.hibernate.service.jdbc.connections.internal.C3P0ConnectionProvider
    –>

    Reply

  2. Hi
    I have configured c3p0 with Hibernate. It works fine till connections get exhausted to max limit. Then it stops providing responses. So , practically, my web app does not receive any data. No errors in console.
    org.hibernate.connection.C3P0ConnectionProvider
    5
    10
    10
    50
    30
    true

    10
    <!– org.hibernate.service.jdbc.connections.internal.C3P0ConnectionProvider –>

    Tried with “org.hibernate.service.jdbc.connections.internal.C3P0ConnectionProvider” also.

    My sessionFactory creation class is as below:
    public class DBConfiguration {

    private static SessionFactory sessionFactory = setSessionFactory();

    private static SessionFactory setSessionFactory() {
    Configuration configuration = null;
    configuration = new Configuration().configure(“hibernate.cfg.xml”);
    StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties());

    return configuration.buildSessionFactory(builder.build());
    }

    public static SessionFactory getSessionFactory() {
    if(sessionFactory == null) {
    sessionFactory = setSessionFactory();
    }
    return sessionFactory;
    }

    public static void closeSessionFactory() {
    sessionFactory.close();
    }
    }

    I have done session.flush() and session.close() after every DB queries.

    It seems that the connection is not released from the pool for another client to use. Hence after max number of connections is reached, it is waiting for one to be released, which is not happening.
    I tried with 50 as max limit, it stays for longer than stops.
    Am I missing something?

    Thanks

    Reply

    • Please share your persistence.xml/hibernate-cfg.xml after masking any sensitive data.

      Reply

  3. Is it possible to modify all properties at runtime? For instance, if I encounter that the value of maximum connections needs to be increased, can I do this without re-starting the CP?

    Reply

  4. sir if am creating a connection pool in tomcat with c3p0 then how to use it in hibernate

    Reply

    • As mentioned in post, all you need to do is define any property in hibernate config file starting with “hibernate.c3p0.”. Then hibernate will take care of everything in backend.

      Reply

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