You are defining your resource folder correctly, and Gradle with the Spring Boot plugin will automatically add it to the classpath. If that didn't happen, Spring would also not be able to load your application.properties file either, which I assume it does.

I also assume that you want to use Hibernate to load your data, as that is the default behavior if you have a file called import.sql. But it only does this if the ddl-auto property is set to create or create-drop, and yours is update.

You could also let Spring Boot handle the datasource initialization instead of Hibernate, but you it will still only happen when the schema is (re-)created, and not when just connecting to it.

Also, even though this is not the cause of your problems, I don't believe classpath resources in Spring should be prefixed with slash, but at the very least not two (classpath://import.sql).

I came across the following solution, which solved this issue for me.

Basically, the BootRunTask extends the standard JavaExec task, which offers a classpath option. So, you can add the test classpath resources by using the following gradle configuration:

bootRun {
    classpath = sourceSets.test.runtimeClasspath
}

/src/main/resources is a Maven project structure convention. It's a path inside your project where you place resources. During the build step, Maven will take files in there and place them in the appropriate place for you to use them in your runtime classpath, eg in an executable .jar, some physical file system location used in the classpath (with java's -cp option), etc.

I could choose to build my application myself or with a different build tool. In such a case, /src/main/resources would not exist. However, the intention is for the classpath to be the same, ie. to contain the same resources and .class files.

The Spring boot documentation talks about the classpath because it shouldn't make assumptions about how your project is set up.