Spring doesn't see h2 database hence complain about database not available

Question

I'm building a simple reactive web application ( Following Josh long's tech talk ) Simply put I have reactive web, r2dbc and h2 as dependencies.

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-webflux</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-r2dbc</artifactId>
    </dependency>
    <dependency>
        <groupId>com.h2database</groupId>
        <artifactId>h2</artifactId>
        <scope>runtime</scope>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>io.projectreactor</groupId>
        <artifactId>reactor-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

So I expect spring would configure everything for me( It does for Josh ). But I get error saying not being able to connect to a database and there is a suggestion asking to include h2(which I already have). What am I doing wrong here?

Description:

Failed to configure a ConnectionFactory: 'url' attribute is not specified and no embedded database could be configured.

Reason: Failed to determine a suitable R2DBC Connection URL


Action:

Consider the following:
    If you want an embedded database (H2), please put it on the classpath.
    If you have database settings to be loaded from a particular profile you may need to activate it (no profiles are currently active).

Answer 1

Ok it was missing r2dbc-h2 dependency. This happened because I didn't add r2dbc when I created the project with start.spring.io then added it and inspect the pom but only copied spring-boot-starter-data-r2dbc.

<dependency>
  <groupId>io.r2dbc</groupId>
  <artifactId>r2dbc-h2</artifactId>
  <scope>runtime</scope>
</dependency>

Still bit confusing though. Spring boot says it looks in to the class path and auto configure dependencies but seems like sometimes it need given combination of dependencies.