Getting ArtifactId and Version in Spring Boot Starter

The other answer is completely correct. Just for others finding this question in case you are using Gradle instead of Maven:

Generating build info is as simple as adding this to your build.gradle file:

plugins {
    id 'org.springframework.boot' version '<your-boot-version>.RELEASE'
}

// ...    

springBoot {
    buildInfo()
}

And if you want to pass custom properties:

springBoot {
    buildInfo {
        properties {
            additional = [
                'property.name': 'property value',
                'other.property': 'different.value'
            ]
        }
    }
}

Then the usage in Java code is the same using BuildProperties. You can find more info about the plugin in this guide.

After a lot of effort, I found a surprisingly simple answer. This is how spring-boot-actuator gets the information.

The Spring Boot Maven plugin comes equipped with a build-info goal. As long as this goal is triggered in the main project Spring has a BuildProperties class you can wire in for the information.

            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <id>build-info</id>
                        <goals>
                            <goal>build-info</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

You can access the properties in your starter like:

@Autowired
BuildProperties buildProperties;

...
buildProperties.getArtifact();
buildProperties.getVersion();

You can even specify additional properties from the plugin. See the plugin documentation for more details: https://docs.spring.io/spring-boot/docs/current/maven-plugin/build-info-mojo.html

Unfortunately I never quite got to fully understand why I could not access the correct manifest, but this should help anyone else trying to solve this problem.