config-application-dev.properties: |
    server.port=5001
    server.compression.enabled=true
    azure.keyvault.uri=<URL>
    azure.keyvault.client-id=<CLIENTID>
    azure.keyvault.client-key=<CLIENTKEY>

@PropertySource({ "${propertiesDir}/${envTarget}/config/config-application-${envTarget}.properties" })
public class Application{
   ...
}

@Value("${azure-key-vault-secret}")
private String mySecretProperty;

2019-08-21 16:17:26.051  WARN 1 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException:
 Error creating bean with name 'exampleController': Injection of autowired dependencies failed; nested exception is java.lang.IllegalArgumentException: Could not resolve placeholder 'secret-in-keyvault' in value "${secret-in-keyvault}"