feat: add PORT env var to support deployment on Heroku (#203)

* feat: support specifying server port using the PORT environment variable

This allows it to run on Heroku.

Author: bethesque

README.md

@@ -213,7 +213,7 @@ The standalone server supports the following configuration by `ENV` variables:
 | Variable | Description |
 | --- | --- |
 | `SERVER_HOSTNAME`| Lets the standalone server bind to a specific hostname, by default it binds to `0.0.0.0` |
-| `SERVER_PORT`| The port that the standalone server will listen to, defaults to `8080` |
+| `SERVER_PORT` or `PORT` | The port that the standalone server will listen to, defaults to `8080`. The `PORT` environment variable may be used to [run the Docker image on Heroku](https://devcenter.heroku.com/articles/container-registry-and-runtime#pushing-an-existing-image) as per the documentation [here](https://devcenter.heroku.com/articles/setting-the-http-port-for-java-applications). |
 | `JSON_CONFIG_PATH`| The absolute path to a json file containing configuration about the OAuth2 part of the server (`OAuth2Config`). More details on the format below. |
 | `JSON_CONFIG`| The actual JSON content of `OAuth2Config`, this ENV var takes precedence over the `JSON_CONFIG_PATH` var. More details on the format below.|
 

src/main/kotlin/no/nav/security/mock/oauth2/StandaloneMockOAuth2Server.kt

@@ -16,11 +16,12 @@ object StandaloneConfig {
     const val JSON_CONFIG_PATH = "JSON_CONFIG_PATH"
     const val SERVER_HOSTNAME = "SERVER_HOSTNAME"
     const val SERVER_PORT = "SERVER_PORT"
+    const val PORT = "PORT" // Supports running Docker image on Heroku.
 
     fun hostname(): InetAddress = SERVER_HOSTNAME.fromEnv()
         ?.let { InetAddress.getByName(it) } ?: InetSocketAddress(0).address
 
-    fun port(): Int = SERVER_PORT.fromEnv()?.toInt() ?: 8080
+    fun port(): Int = (SERVER_PORT.fromEnv()?.toInt() ?: PORT.fromEnv()?.toInt())?: 8080
 
     fun oauth2Config(): OAuth2Config = with(jsonFromEnv()) {
         if (this != null) {

src/test/kotlin/no/nav/security/mock/oauth2/StandaloneMockOAuth2ServerKtTest.kt

@@ -9,6 +9,8 @@ import io.kotest.matchers.shouldBe
 import io.kotest.matchers.types.beInstanceOf
 import no.nav.security.mock.oauth2.StandaloneConfig.JSON_CONFIG
 import no.nav.security.mock.oauth2.StandaloneConfig.JSON_CONFIG_PATH
+import no.nav.security.mock.oauth2.StandaloneConfig.SERVER_PORT
+import no.nav.security.mock.oauth2.StandaloneConfig.PORT
 import no.nav.security.mock.oauth2.StandaloneConfig.hostname
 import no.nav.security.mock.oauth2.StandaloneConfig.oauth2Config
 import no.nav.security.mock.oauth2.StandaloneConfig.port
@@ -31,6 +33,28 @@ internal class StandaloneMockOAuth2ServerKtTest {
         port() shouldBe 8080
     }
 
+    @Test
+    fun `with the environment variable SERVER_PORT set`() {
+        withEnvironment(SERVER_PORT to "9292") {
+            port() shouldBe 9292
+        }
+    }
+
+    @Test
+    fun `with the environment variable PORT set`() {
+        withEnvironment(PORT to "9292") {
+            port() shouldBe 9292
+        }
+    }
+
+    @Test
+    fun `with the environment variables SERVER_PORT and PORT set`() {
+        withEnvironment(mapOf(SERVER_PORT to "9292", PORT to "9393")) {
+            port() shouldBe 9292
+        }
+    }
+
+
     @Test
     fun `load oauth2Config from file`() {
         withEnvironment(JSON_CONFIG_PATH to configFile) {