Spring Boot 2 + JdbcTemplate - is there a way to provide SQL query for each database supported? - spring

Question

I'm working on a Spring Boot 2.4.2 based project and using "spring-boot-starter-jdbc" and "com.oracle.database.jdbc" for Oracle Jdbc driver.
As I use JdbcTemplate to interact with DB, everything seems clean and easy. But I may need to support multiple database types in future - Oracle, SQL Server, MySQL, DB2, etc.
Did quite a bit of Googling but did not find any option for this..
Like mentioned above, I am using Spring-Jdbc (not Spring Data JDBC or Spring Data JPA) - how do I provide the SQL queries specific to each database supported in the code or configuration?
Please, let me know your thoughts. Thanks.

Answer 1

I'm not familiar with Spring JDBC, but you could user Spring dependency injection mechanism to create a profile for each database.
First an interface:
public interface DbQueries {
String createQueryForSelectingUsers();
}
Then implement the interface for each supported database:
#Profile("mysql")
#Component
public class MySqlDbQueries implements DbQueries {
#Override
public String createQueryForSelectingUsers() {
return "SELECT * FROM USER";
}
}
2nd example:
#Profile("oracle")
#Component
public class OracleDbQueries implements DbQueries {
#Override
public String createQueryForSelectingUsers() {
return "SELECT * FROM USER";
}
}
Afterwards use it where you need it:
public class MyRepository {
private DbQueries dbQueries;
// DbQueries implementation will be injected based on your current profile
public MyRepository(DbQueries dbQueries) {
this.dbQueries = dbQueries;
}
public void printAllUsers() {
String query = dbQueries.createQueryForSelectingUsers();
// stuff to execute query
}
}
Remember to start your app with a profile with e.q. --spring.profiles.active=mysql or adding active profile information into application.properties:
spring.profiles.active=mysql