How to find port of Spring Boot container when running a spock test using property server.port=0

Question

Given this entry in application.properties:

server.port=0

which causes Spring Boot to chose a random available port, and testi

Answer 1

The injection will work with Spock, as long as you've configured your spec class correctly and have spock-spring on the classpath. There's a limitation in Spock Spring which means it won't bootstrap your Boot application if you use @SpringApplicationConfiguration. You need to use @ContextConfiguration and configure it manually instead. See this answer for the details.

The second part of the problem is that you can't use a GString for the @Value. You could escape the $, but it's easier to use single quotes:

@Value('${local.server.port}')
private int port;

Putting this together, you get a spec that looks something like this:

@ContextConfiguration(loader = SpringApplicationContextLoader, classes = SampleSpockTestingApplication.class)
@WebAppConfiguration
@IntegrationTest("server.port=0")
class SampleSpockTestingApplicationSpec extends Specification {

    @Value("\${local.server.port}")
    private int port;

    def "The index page has the expected body"() {
        when: "the index page is accessed"
        def response = new TestRestTemplate().getForEntity(
            "http://localhost:$port", String.class);
        then: "the response is OK and the body is welcome"
        response.statusCode == HttpStatus.OK
        response.body == 'welcome'
    }
}

Also note the use of @IntegrationTest("server.port=0") to request a random port be used. It's a nice alternative to configuring it in application.properties.