Add examples for polymorphic type handling

Example implementations exist for both Java and Scala.

build.sbt

@@ -38,8 +38,8 @@ lazy val root = (project in file("."))
   )
   .aggregate(
     testLib, configLib,
-    simpleLibScala, simpleAppScala, complexAppScala,
-    simpleLibJava, simpleAppJava, complexAppJava
+    simpleLibScala, simpleAppScala, complexAppScala, polymorphicAppScala,
+    simpleLibJava, simpleAppJava, complexAppJava, polymorphicAppJava
   )
 
 lazy val configLib =  Project("config", file("config"))
@@ -60,10 +60,12 @@ lazy val testLib = proj("config-test-lib", file("test-lib"))
 lazy val simpleLibScala  = proj("config-simple-lib-scala",  file("examples/scala/simple-lib"))  dependsOn configLib
 lazy val simpleAppScala  = proj("config-simple-app-scala",  file("examples/scala/simple-app"))  dependsOn simpleLibScala
 lazy val complexAppScala = proj("config-complex-app-scala", file("examples/scala/complex-app")) dependsOn simpleLibScala
+lazy val polymorphicAppScala = proj("config-polymorphic-app-scala", file("examples/scala/polymorphic-app")) dependsOn configLib
 
 lazy val simpleLibJava  = proj("config-simple-lib-java",  file("examples/java/simple-lib"))  dependsOn configLib
 lazy val simpleAppJava  = proj("config-simple-app-java",  file("examples/java/simple-app"))  dependsOn simpleLibJava
 lazy val complexAppJava = proj("config-complex-app-java", file("examples/java/complex-app")) dependsOn simpleLibJava
+lazy val polymorphicAppJava = proj("config-polymorphic-app-java", file("examples/java/polymorphic-app")) dependsOn configLib
 
 useGpg := true
 

examples/java/polymorphic-app/src/main/java/PolymorphicApp.java

@@ -0,0 +1,52 @@
+import com.typesafe.config.Config;
+import com.typesafe.config.ConfigBeanFactory;
+import com.typesafe.config.ConfigFactory;
+import logging.Appender;
+
+import java.util.List;
+
+class PolymorphicApp {
+
+    public static class LoggerConfiguration {
+
+        private String level;
+        private List<Appender> appenders;
+
+        public String getLevel() {
+            return level;
+        }
+
+        public void setLevel(String level) {
+            this.level = level;
+        }
+
+        public List<Appender> getAppenders() {
+            return appenders;
+        }
+
+        public void setAppenders(List<Appender> appenders) {
+            this.appenders = appenders;
+        }
+    }
+
+    public static void main(String[] args) {
+        // This app is "polymorphic" because we have one interface type with
+        // multiple implementations that are deserialized to correct type based
+        // on the type defined in configuration.
+
+        // Java version showcases two types of defining subtypes and naming
+        // them: defining one subtype in the main interface, and one in the
+        // 'META-INF/services' directory.
+
+        Config config = ConfigFactory.load("polymorphic");
+
+        LoggerConfiguration loggerConfiguration =
+            ConfigBeanFactory.create(config.getConfig("polymorphic-app.logger"), LoggerConfiguration.class);
+
+        String demoMessage = config.getString("polymorphic-app.demo-message");
+
+        for (Appender appender : loggerConfiguration.getAppenders()) {
+            appender.log(demoMessage);
+        }
+    }
+}

examples/java/polymorphic-app/src/main/java/logging/Appender.java

@@ -0,0 +1,14 @@
+package logging;
+
+import com.typesafe.config.ConfigSubTypes;
+import com.typesafe.config.ConfigSubTypes.Type;
+import com.typesafe.config.ConfigTypeInfo;
+
+@ConfigTypeInfo
+@ConfigSubTypes({
+    @Type(value = ConsoleAppender.class, name = "console")
+})
+public interface Appender {
+
+    void log(String event);
+}

examples/java/polymorphic-app/src/main/java/logging/ConsoleAppender.java

@@ -0,0 +1,20 @@
+package logging;
+
+public class ConsoleAppender implements Appender {
+
+    private String target;
+
+    public String getTarget() {
+        return target;
+    }
+
+    public void setTarget(String target) {
+        this.target = target;
+    }
+
+    @Override
+    public void log(String event) {
+        System.out.printf("Logging to '%s' using console logger: %s\n",
+            target, event);
+    }
+}

examples/java/polymorphic-app/src/main/java/logging/SyslogAppender.java

@@ -0,0 +1,41 @@
+package logging;
+
+import com.typesafe.config.ConfigTypeName;
+
+@ConfigTypeName("syslog")
+public class SyslogAppender implements Appender {
+
+    private String host;
+    private int port;
+    private String facility;
+
+    public String getHost() {
+        return host;
+    }
+
+    public void setHost(String host) {
+        this.host = host;
+    }
+
+    public int getPort() {
+        return port;
+    }
+
+    public void setPort(int port) {
+        this.port = port;
+    }
+
+    public String getFacility() {
+        return facility;
+    }
+
+    public void setFacility(String facility) {
+        this.facility = facility;
+    }
+
+    @Override
+    public void log(String event) {
+        System.out.printf("Logging to '%s/%d/%s' using syslog logger: %s\n",
+            host, port, facility, event);
+    }
+}

examples/java/polymorphic-app/src/main/resources/META-INF/services/logging.Appender

@@ -0,0 +1 @@
+logging.SyslogAppender

examples/java/polymorphic-app/src/main/resources/polymorphic.conf

@@ -0,0 +1,18 @@
+polymorphic-app {
+    logger={
+        level="INFO"
+        appenders=[
+            {
+                type="console"
+                target="stderr"
+            }
+            {
+                type="syslog"
+                host="localhost"
+                port=514
+                facility="local0"
+            }
+        ]
+    }
+    demo-message="hello from java"
+}

examples/scala/polymorphic-app/src/main/resources/META-INF/services/logging.Appender

@@ -0,0 +1,2 @@
+logging.ConsoleAppender
+logging.SyslogAppender

examples/scala/polymorphic-app/src/main/resources/polymorphic.conf

@@ -0,0 +1,18 @@
+polymorphic-app {
+    logger={
+        level="INFO"
+        appenders=[
+            {
+                type="console"
+                target="stderr"
+            }
+            {
+                type="syslog"
+                host="localhost"
+                port=514
+                facility="local0"
+            }
+        ]
+    }
+    demo-message="hello from scala"
+}

examples/scala/polymorphic-app/src/main/scala/PolymorphicApp.scala

@@ -0,0 +1,30 @@
+import com.typesafe.config._
+import logging.Appender
+
+import scala.beans.BeanProperty
+import scala.collection.JavaConversions._
+
+object PolymorphicApp extends App {
+
+    class LoggerConfiguration {
+        @BeanProperty var level: String = _
+        @BeanProperty var appenders: java.util.List[Appender] = _
+    }
+
+    // This app is "polymorphic" because we have one interface type with
+    // multiple implementations that are deserialized to correct type based
+    // on the type defined in configuration.
+
+    // Scala version relies on 'META-INF/services' directory for subtype
+    // discovery due to the fact that annotations have some Java specific
+    // elements.
+
+    val config = ConfigFactory.load("polymorphic")
+
+    val loggerConfiguration =
+        ConfigBeanFactory.create(config.getConfig("polymorphic-app.logger"), classOf[LoggerConfiguration])
+
+    val demoMessage = config.getString("polymorphic-app.demo-message")
+
+    loggerConfiguration.getAppenders.toList.foreach(a => a.log(demoMessage))
+}

examples/scala/polymorphic-app/src/main/scala/logging/Appender.scala

@@ -0,0 +1,9 @@
+package logging
+
+import com.typesafe.config.ConfigTypeInfo
+
+@ConfigTypeInfo
+trait Appender {
+
+    def log(event: String)
+}

examples/scala/polymorphic-app/src/main/scala/logging/ConsoleAppender.scala

@@ -0,0 +1,15 @@
+package logging
+
+import com.typesafe.config.ConfigTypeName
+
+import scala.beans.BeanProperty
+
+@ConfigTypeName("console")
+class ConsoleAppender extends Appender {
+
+    @BeanProperty var target: String = _
+
+    override def log(event: String) {
+        printf("Logging to '%s' using console logger: %s\n", target, event)
+    }
+}

examples/scala/polymorphic-app/src/main/scala/logging/SyslogAppender.scala

@@ -0,0 +1,17 @@
+package logging
+
+import com.typesafe.config.ConfigTypeName
+
+import scala.beans.BeanProperty
+
+@ConfigTypeName("syslog")
+class SyslogAppender extends Appender {
+
+    @BeanProperty var host: String = _
+    @BeanProperty var port: Int = _
+    @BeanProperty var facility: String = _
+
+    override def log(event: String) {
+        printf("Logging to '%s/%d/%s' using syslog logger: %s\n", host, port, facility, event)
+    }
+}