Use configuration

Author: debuglevel

build.gradle

@@ -28,7 +28,7 @@ compileTestKotlin {
 }
 
 group 'de.debuglevel.sparkutils'
-version '0.0.6'
+version '0.0.8'
 
 sourceCompatibility = 1.8
 
@@ -50,6 +50,9 @@ dependencies {
 
     // Spark (REST Server)
     compileOnly 'com.sparkjava:spark-kotlin:1.0.0-alpha'
+
+    // Configuration
+    implementation 'com.natpryce:konfig:1.6.9.0'
 }
 
 dokka {

src/main/kotlin/de/debuglevel/sparkutils/configuration/Configuration.kt

@@ -0,0 +1,51 @@
+package de.debuglevel.sparkutils.configuration
+
+import com.natpryce.konfig.*
+import com.natpryce.konfig.ConfigurationProperties.Companion.systemProperties
+import java.io.File
+
+/**
+ * Configuration of the microservice.
+ *
+ * Provides some usual configurations for a microservice (e.g. used port). Furthermore, the `configuration` variable
+ * exposes access to any defined configuration parameter defined.
+ *
+ * There are multiple possible sources for configurations, where the former override the later:
+ * - Java system properties
+ * - Environment variables
+ * - file `configuration.properties` on the working directory
+ * - file `defaults.properties` in the class path
+ *
+ * For environment variables, "SERVER_PORT" can be used where "server.port" would actually be needed.
+ */
+object MicroserviceConfiguration {
+    private val key_server_port = Key("server.port", intType)
+    private val key_port = Key("port", intType)
+
+    val configuration: Configuration
+
+    init {
+        var config: Configuration = systemProperties()
+
+        config = config overriding
+                EnvironmentVariables()
+
+        config = config overriding
+                ConfigurationProperties.fromOptionalFile(File("configuration.properties"))
+
+        val defaultsPropertiesFilename = "defaults.properties"
+        if (ClassLoader.getSystemClassLoader().getResource(defaultsPropertiesFilename) != null) {
+            config = config overriding
+                    ConfigurationProperties.fromResource(defaultsPropertiesFilename)
+        }
+
+        configuration = config
+    }
+
+    /**
+     * Port on which the REST server listens.
+     *
+     * Defaults to 4567 if none is configured.
+     */
+    val port = configuration.getOrNull(key_port) ?: configuration.getOrNull(key_server_port) ?: 4567
+}

src/main/kotlin/de/debuglevel/sparkutils/port/SparkPortUtils.kt

@@ -1,26 +1,11 @@
 package de.debuglevel.sparkutils.port
 
+import de.debuglevel.sparkutils.configuration.MicroserviceConfiguration
 import mu.KotlinLogging
 import spark.kotlin.port
 
 private val logger = KotlinLogging.logger {}
 
-/**
- * Gets the value of the PORT environment variable, or 4567 if no such environment variable is set.
- *
- * @return value of the PORT environment variable, or 4567 if no such environment variable is set.
- */
-private fun getEnvironmentPort(): Int {
-    // TODO: add more options to figure out a port configuration
-
-    val processBuilder = ProcessBuilder()
-    return if (processBuilder.environment()["PORT"] != null) {
-        Integer.parseInt(processBuilder.environment()["PORT"])
-    } else {
-        4567
-    }
-}
-
 /**
  * Sets the port to a configured port.
  *
@@ -29,7 +14,7 @@ private fun getEnvironmentPort(): Int {
 fun configuredPort() {
     // TODO: Spark fails silently if port is already taken. There should be thrown an exception
 
-    val port = getEnvironmentPort()
+    val port = MicroserviceConfiguration.port
     logger.info("Setting port to $port...")
     port(port)
     //logger.info("Setting port to $port succeeded.")