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

Question

Given this entry in application.properties:
server.port=0
which causes Spring Boot to chose a random available port, and testing a spring boot web application using spock, how can the spock code know which port to hit?
Normal injection like this:
#Value("${local.server.port}")
int port;
doesn't work with spock.

Answer 1

You can find the port using this code:
int port = context.embeddedServletContainer.port
Which for those interested in the java equivalent is:
int port = ((TomcatEmbeddedServletContainer)((AnnotationConfigEmbeddedWebApplicationContext)context).getEmbeddedServletContainer()).getPort();
Here's an abstract class that you can extends which wraps up this initialization of the spring boot application and determines the port:
abstract class SpringBootSpecification extends Specification {
#Shared
#AutoCleanup
ConfigurableApplicationContext context
int port = context.embeddedServletContainer.port
void launch(Class clazz) {
Future future = Executors.newSingleThreadExecutor().submit(
new Callable() {
#Override
public ConfigurableApplicationContext call() throws Exception {
return (ConfigurableApplicationContext) SpringApplication.run(clazz)
}
})
context = future.get(20, TimeUnit.SECONDS);
}
}
Which you can use like this:
class MySpecification extends SpringBootSpecification {
void setupSpec() {
launch(MyLauncher.class)
}
String getBody(someParam) {
ResponseEntity entity = new RestTemplate().getForEntity("http://localhost:${port}/somePath/${someParam}", String.class)
return entity.body;
}
}

Answer 2

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.

Answer 3

You could do this too:
#Autowired
private org.springframework.core.env.Environment springEnv;
...
springEnv.getProperty("server.port");