no POM.xml as dependências estão assim...
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-c3p0</artifactId>
<version>4.3.11.Final</version>
<exclusions>
<exclusion>
<groupId>c3p0</groupId>
<artifactId>c3p0</artifactId>
</exclusion>
<exclusion>
<groupId>com.mchange</groupId>
<artifactId>c3p0</artifactId>
</exclusion>
</exclusions>
</dependency>
<!-- https://mvnrepository.com/artifact/com.mchange/c3p0 -->
<dependency>
<groupId>com.mchange</groupId>
<artifactId>c3p0</artifactId>
<version>0.9.5.2</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>4.3.11.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator-cdi</artifactId>
<version>5.0.1.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>4.3.11.Final</version>
</dependency>
Vi que no hibernate.cfg.xml tem essas configurações feitas para o c3p0
<property name="hibernate.dialect">${db.dialect}</property>
<property name="hibernate.c3p0.min_size">${db.min_size}</property>
<property name="hibernate.c3p0.max_size">${db.max_size}</property>
<property name="hibernate.c3p0.timeout">300</property>
<property name="hibernate.c3p0.acquire_increment">1</property>
<property name="hibernate.c3p0.max_statements">100</property>
<property name="hibernate.c3p0.idle_test_period">300</property>
<property name="hibernate.c3p0.validate">true</property>
<property name="hibernate.connection.provider_class">org.hibernate.service.jdbc.connections.internal.C3P0ConnectionProvider</property>
<property name="hibernate.transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property>
<property name="connection.autoReconnect">true</property>
<property name="connection.autoReconnectForPools">true</property>
<property name="connection.is-connection-validation-required">true</property>
minha dúvida é em relação à configuração por exemplo, a url do banco e demais configurações utilizo um arquivo catalina.properties
#Oracle - DEV
db.username=abcde
db.password=abdce123
db.url=jdbc:oracle:thin:@127.0.0.1:1521:dev
db.default_schema=desenvolvimento
db.dialect=org.hibernate.dialect.Oracle10gDialect
db.driver=oracle.jdbc.driver.OracleDriver
ou se devo alterar em mais lugares para que não dê problemas.