How to set custom connection properties on DataSource in Spring Boot 1.3.x with default Tomcat connection pool - spring-boot

Question

I need to set some specific Oracle JDBC connection properties in order to speed up batch INSERTs (defaultBatchValue) and mass SELECTs (defaultRowPrefetch).
I got suggestions how to achieve this with DBCP (Thanks to M. Deinum) but I would like to:
keep the default Tomcat jdbc connection pool
keep application.yml for configuration
I was thinking about a feature request to support spring.datasource.custom_connection_properties or similar in the future and because of this tried to pretent this was already possible. I did this by passing the relevant information while creating the DataSource and manipulated the creation of the DataSource like this:
#Bean
public DataSource dataSource() {
DataSource ds = null;
try {
Field props = DataSourceBuilder.class.getDeclaredField("properties");
props.setAccessible(true);
DataSourceBuilder builder = DataSourceBuilder.create();
Map<String, String> properties = (Map<String, String>) props.get(builder);
properties.put("defaultRowPrefetch", "1000");
properties.put("defaultBatchValue", "1000");
ds = builder.url( "jdbc:oracle:thin:#xyz:1521:abc" ).username( "ihave" ).password( "wonttell" ).build();
properties = (Map<String, String>) props.get(builder);
log.debug("properties after: {}", properties);
} ... leaving out the catches ...
}
log.debug("We are using this datasource: {}", ds);
return ds;
}
In the logs I can see that I am creating the correct DataSource:
2016-01-18 14:40:32.924 DEBUG 31204 --- [ main] d.a.e.a.c.config.DatabaseConfiguration : We are using this datasource: org.apache.tomcat.jdbc.pool.DataSource#19f040ba{ConnectionPool[defaultAutoCommit=null; ...
2016-01-18 14:40:32.919 DEBUG 31204 --- [ main] d.a.e.a.c.config.DatabaseConfiguration : properties after: {password=wonttell, driverClassName=oracle.jdbc.OracleDriver, defaultRowPrefetch=1000, defaultBatchValue=1000, url=jdbc:oracle:thin:#xyz:1521:abc, username=ihave}
The actuator shows me that my code replaced the datasource:
But the settings are not activated, which I can see while profiling the application. The defaultRowPrefetch is still at 10 which causes my SELECTs to be much slower than they would be if 1000 was activated.

Answer 1

Setting the pools connectionProperties should work. Those will be passed to the JDBC driver. Add this to application.properties:
spring.datasource.connectionProperties: defaultRowPrefetch=1000;defaultBatchValue=1000
Edit (some background information):
Note also that you can configure any of the DataSource implementation
specific properties via spring.datasource.*: refer to the
documentation of the connection pool implementation you are using for
more details.
source: spring-boot documentation

Answer 2

As Spring Boot is EOL for a long time I switched to Spring Boot 2.1 with its new default connection pool Hikari. Here the solution is even more simply and can be done in the application.properties or (like shown here) application.yml:
spring:
datasource:
hikari:
data-source-properties:
defaultRowPrefetch: 1000
(In a real-life config there would be several other configuration items but as they are not of interest for the question asked I simply left them out in my example)

Answer 3

Some additional information to complement the answer by #Cyril. If you want to upvote use his answer, not mine.
I was a little bit puzzled how easy it is to set additional connection properties that in the end get used while creating the database connection. So I did a little bit of research.
spring.datasource.connectionProperties is not mentioned in the reference. I created an issue because of this.
If I had used the Spring Boot YML editor, I would have seen which properties are supported. Here is what STS suggests when you create an application.yml and hit Ctrl+Space:
The dash does not matter because of relaxed binding but if you interpret it literally the propertys name is spring.datasource.connection-properties.
The correct setup in application.yml looks like this:
spring:
datasource:
connection-properties: defaultBatchValue=1000;defaultRowPrefetch=1000
...
This gets honored which is proven by my perf4j measurements of mass SELECTs.
Before:
2016-01-19 08:58:32.604 INFO 15108 --- [ main]
org.perf4j.TimingLogger : start[1453190311227]
time[1377] tag[get elements]
After:
2016-01-19 08:09:18.214 INFO 9152 --- [ main]
org.perf4j.TimingLogger : start[1453187358066]
time[147] tag[get elements]
The time taken to complete the SQL statement drops from 1377ms to 147, which is an enormous gain in performance.

Answer 4

After digging around in the Tomcat code for a bit, I found that the dataSource.getPoolProperties().getDbProperties() is the Properties object that will actually get used to generate connections for the pool.
If you use the BeanPostProcessor approach mentioned by #m-deinum, but instead use it to populate the dbProperties like so, you should be able to add the properties in a way that makes them stick and get passed to the Oracle driver.
import java.util.Properties;
import org.apache.tomcat.jdbc.pool.DataSource;
import org.apache.tomcat.jdbc.pool.PoolConfiguration;
#Component
public class OracleConfigurer implements BeanPostProcessor {
#Override
public Object postProcessBeforeInitialization(Object bean, String name) throws BeansException {
if (bean instanceof DataSource) {
DataSource dataSource = (DataSource)bean;
PoolConfiguration configuration = dataSource.getPoolProperties();
Properties properties = configuration.getDbProperties();
if (null == properties) properties = new Properties();
properties.put("defaultRowPrefetch", 1000);
properties.put("defaultBatchValue", 1000);
configuration.setDbProperties(properties);
}
return bean;
}
#Override
public Object postProcessAfterInitialization(Object bean, String name) throws BeansException {
return bean;
}
}