Add default no-op method to SpringApplicationRunListener

See gh-16104

Author: ayudovin

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/SpringApplicationRunListener.java

@@ -31,35 +31,40 @@
  * @author Phillip Webb
  * @author Dave Syer
  * @author Andy Wilkinson
+ * @author Artsiom Yudovin
  */
 public interface SpringApplicationRunListener {
 
 	/**
 	 * Called immediately when the run method has first started. Can be used for very
 	 * early initialization.
 	 */
-	void starting();
+	default void starting() {
+	}
 
 	/**
 	 * Called once the environment has been prepared, but before the
 	 * {@link ApplicationContext} has been created.
 	 * @param environment the environment
 	 */
-	void environmentPrepared(ConfigurableEnvironment environment);
+	default void environmentPrepared(ConfigurableEnvironment environment) {
+	}
 
 	/**
 	 * Called once the {@link ApplicationContext} has been created and prepared, but
 	 * before sources have been loaded.
 	 * @param context the application context
 	 */
-	void contextPrepared(ConfigurableApplicationContext context);
+	default void contextPrepared(ConfigurableApplicationContext context) {
+	}
 
 	/**
 	 * Called once the application context has been loaded but before it has been
 	 * refreshed.
 	 * @param context the application context
 	 */
-	void contextLoaded(ConfigurableApplicationContext context);
+	default void contextLoaded(ConfigurableApplicationContext context) {
+	}
 
 	/**
 	 * The context has been refreshed and the application has started but
@@ -68,7 +73,8 @@ public interface SpringApplicationRunListener {
 	 * @param context the application context.
 	 * @since 2.0.0
 	 */
-	void started(ConfigurableApplicationContext context);
+	default void started(ConfigurableApplicationContext context) {
+	}
 
 	/**
 	 * Called immediately before the run method finishes, when the application context has
@@ -77,7 +83,8 @@ public interface SpringApplicationRunListener {
 	 * @param context the application context.
 	 * @since 2.0.0
 	 */
-	void running(ConfigurableApplicationContext context);
+	default void running(ConfigurableApplicationContext context) {
+	}
 
 	/**
 	 * Called when a failure occurs when running the application.
@@ -86,6 +93,7 @@ public interface SpringApplicationRunListener {
 	 * @param exception the failure
 	 * @since 2.0.0
 	 */
-	void failed(ConfigurableApplicationContext context, Throwable exception);
+	default void failed(ConfigurableApplicationContext context, Throwable exception) {
+	}
 
 }