Failed to get driver instance

Your URL seems wrong. As far as I remember, it should be:

jdbc:hsqldb:hsql://localhost:9001/devel

And also, you didn't provide driver class name (org.hsqldb.jdbc.JDBCDriver).

config.setDriverClassName("org.hsqldb.jdbc.JDBCDriver");

If you are using Spring Boot 1.4, there's no need for explicit definition of data source when using HikariCP. As stated in documentation.

java spring spring-boot hsqldb hikaricp

config.addDataSourceProperty("useSSL",false); may be useful.

java spring spring-boot hsqldb hikaricp

As per documentation, the correct line should be

config.setJdbcUrl("jdbc:hsqldb:hsql://localhost:9001/devel");

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