But in that case, we will have a basic out-of-the-box configuration. There will be many cases where we will need some advanced configurations. Let’s see some of them.

3.3. Oracle Universal Connection Pooling

If we want to use advanced configurations, we can declare the UCP datasource and set the remaining properties in the application.properties file. Currently, the best way to enable UCP in a spring-boot application is through the Oracle-provided spring-boot-starter library.

Oracle Universal Connection Pool (UCP) for JDBC provides a full-featured implementation for caching JDBC connections. It reuses the connections instead of creating new ones. It also gives us a set of properties for customizing pool behaviour.

If we want to use UCP, we need to add the following Maven dependency:

<dependency>
   <groupId>com.oracle.database.spring</groupId>
   <artifactId>oracle-spring-boot-starter-ucp</artifactId>
   <version>3.1.0</version> <!-- 2.7.7 for Spring Boot 2.x -->
   <type>pom</type>
</dependency>

Now we only have to add our configuration into the application.properties file:

# UCP settings
spring.datasource.type=oracle.oracleucp.jdbc.PoolDataSource
spring.datasource.oracleucp.connection-factory-class-name=oracle.jdbc.pool.OracleDataSource 
spring.datasource.oracleucp.sql-for-validate-connection=select * from dual 
spring.datasource.oracleucp.connection-pool-name=UcpPoolBooks 
spring.datasource.oracleucp.initial-pool-size=5 
spring.datasource.oracleucp.min-pool-size=5 
spring.datasource.oracleucp.max-pool-size=10

In the above example, we’ve customized some pool properties:

If we need to add more configuration properties, we should check the UCPDataSource JavaDoc or the developer’s guide .

4. Older Oracle Versions

For versions before 11.2, like Oracle 9i or 10g , we should create an OracleDataSource instead of using Oracle’s Universal Connection Pooling.

@Configuration
@Profile("oracle")
public class OracleConfiguration {
    @Bean
    public DataSource dataSource() throws SQLException {
        OracleDataSource dataSource = new OracleDataSource();
        dataSource.setUser("books");
        dataSource.setPassword("books");
        dataSource.setURL("jdbc:oracle:thin:@//localhost:11521/ORCLPDB1");
        dataSource.setFastConnectionFailoverEnabled(true);
        dataSource.setImplicitCachingEnabled(true);
        dataSource.setConnectionCachingEnabled(true);
        return dataSource;
In the above example, we created the OracleDataSource for connection pooling and configuring some parameters. We can check all the configurable parameters on the OracleDataSource JavaDoc.
5. Conclusion
Nowadays, configuring Oracle database connection pooling using Spring is a piece of cake.
We’ve seen how to do it just using autoconfiguration and programmatically. Even though Spring recommends the use of HikariCP, other options are available. We should be careful and choose the correct implementation for our current needs.
And as always, the complete example can be found on GitHub.
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