Fix example of functional bean registration

See Diskussion: spring-projects/spring-boot#8115

Author: michael-simons

src/main/java/de/springbootbuch/extconfig/Application.java

@@ -4,31 +4,25 @@
 import org.springframework.boot.CommandLineRunner;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
-import org.springframework.context.support.GenericApplicationContext;
 
 @SpringBootApplication
 public class Application implements CommandLineRunner {
 
     /**
      * The main entry for the JVM.
-     * @param args 
+     * @param args
      */
-    public static void main(String... args) {        
-        final SpringApplication springApplication = new SpringApplication(Application.class);
-        springApplication.addInitializers((GenericApplicationContext ctx) -> {
-            ctx.registerBean(Greeter.class, Greeter::new);
-        });
-        
-        springApplication.run(args);
+    public static void main(String... args) {
+        SpringApplication.run(Application.class, args);
     }
-    
+
     private final String greeting;
-    
+
     /** The dependency on an example service, injected via the constructor. */
     private final ExampleService exampleService;
 
     private final Greeter greeter;
-    
+
     public Application(
             @Value("${example.the-greeting:No greeting available}") final String greeting,
             final ExampleService exampleService,
@@ -42,9 +36,9 @@ public Application(
     /**
      * The entry point for running Spring Boot applications as command line applications.
      * Note that this isn't a static method like the {@link #main(java.lang.String...) }.
-     * 
-     * @param args 
-     * @throws Exception 
+     *
+     * @param args
+     * @throws Exception
      */
     @Override
     public void run(String... args) throws Exception {

src/main/java/de/springbootbuch/extconfig/FunctionalBeanRegistration.java

@@ -0,0 +1,13 @@
+package de.springbootbuch.extconfig;
+
+import org.springframework.context.ApplicationContextInitializer;
+import org.springframework.context.support.GenericApplicationContext;
+
+public class FunctionalBeanRegistration implements ApplicationContextInitializer<GenericApplicationContext> {
+
+    @Override
+    public void initialize(GenericApplicationContext ctx) {
+        ctx.registerBean(Greeter.class, Greeter::new);
+    }
+
+}

src/main/resources/META-INF/spring.factories

@@ -0,0 +1,2 @@
+org.springframework.context.ApplicationContextInitializer=\
+de.springbootbuch.extconfig.FunctionalBeanRegistration