How use the C3P0 JDBC connection pool in your Maven Project.

See the link below for more details about the C3P0 JDBC connection pool : 

• Hibernate Documentation
• HowTo configure the C3P0 connection pool

 In the "pom.xml" file of your ejb project :

Add the dependencies below:

<dependency>
 <groupId>c3p0</groupId>
 <artifactId>c3p0</artifactId>
 <version>0.9.1.2</version> 
</dependency> 
<dependency>
 <groupId>org.hibernate</groupId>
 <artifactId>hibernate-c3p0</artifactId>
 <version>4.2.20.Final</version> 
</dependency>

In the "persistence.xml" file of your ejb project, in the <properties> tag, add the property below:

<property name="hibernate.connection.url" value="${jdbc.connection.url}" /> 
<property name="hibernate.connection.driver_class" value="${jdbc.driver.class}" /> 
<property name="hibernate.connection.username" value="${jdbc.user}" /> 
<property name="hibernate.connection.password" value="${jdbc.password}" /> 
<property name="hibernate.connection.provider_class" value="org.hibernate.connection.C3P0ConnectionProvider" /> 
<property name="hibernate.c3p0.min_size" value="${min.pool.size}" /> 
<property name="hibernate.c3p0.max_size" value="${max.pool.size}" /> 
<property name="hibernate.c3p0.max_statements" value="50" />
<property name="hibernate.c3p0.acquire_increment" value="1" />
<!-- new values for fixing the DB issues with Jboss7 -->
<property name="hibernate.c3p0.idle_test_period" value="40" /> 
<property name="hibernate.c3p0.timeout" value="30" />
<!-- new properties that fix the DB issues we have in Jboss 7 -->
<property name="hibernate.c3p0.unreturnedConnectionTimeout" value="400"/>
<property name="hibernate.c3p0.debugUnreturnedConnectionStackTraces" value="true"/>

In the parent POM of your project, be sure to have, In the <properties> tag of each <profile> :

<jdbc.connection.url>jdbc:postgresql:your-data-base-name</jdbc.connection.url> 
<jdbc.driver.class>org.postgresql.Driver</jdbc.driver.class> 
<jdbc.user>username</jdbc.user> 
<jdbc.password>password</jdbc.password> 
<min.pool.size>1</min.pool.size> 
<max.pool.size>3</max.pool.size>