Make use of new GetMapping and PostMapping annotations

Closes gh-5277

spring-boot-samples/spring-boot-sample-actuator-log4j2/src/main/java/sample/actuator/log4j2/SampleController.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2014 the original author or authors.
+ * Copyright 2012-2016 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,6 +21,7 @@ import java.util.Map;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Controller;
+import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.ResponseBody;
 
@@ -30,7 +31,7 @@ public class SampleController {
 	@Autowired
 	private HelloWorldService helloWorldService;
 
-	@RequestMapping("/")
+	@GetMapping("/")
 	@ResponseBody
 	public Map<String, String> helloWorld() {
 		return Collections.singletonMap("message",