Polish standard Spring MVC exception handling

Rename ExceptionHandlerSupport to ResponseEntityExceptionHandler and
emphasize the contrast to DefaultHandlerExceptionResovler -- i.e.
one returns a ResponseEntity and relies on message converters while
the other returns a ModelAndView and relies on view resolution.

Issue: SPR-9290

spring-web/src/main/java/org/springframework/web/HttpRequestMethodNotSupportedException.java

@@ -17,8 +17,13 @@
 package org.springframework.web;
 
 import java.util.Collection;
+import java.util.HashSet;
+import java.util.Set;
+
 import javax.servlet.ServletException;
 
+import org.springframework.http.HttpMethod;
+
 /**
  * Exception thrown when a request handler does not support a
  * specific request method.
@@ -95,4 +100,15 @@ public class HttpRequestMethodNotSupportedException extends ServletException {
 		return this.supportedMethods;
 	}
 
+	/**
+	 * Return the actually supported HTTP methods, if known, as {@link HttpMethod} instances.
+	 */
+	public Set<HttpMethod> getSupportedHttpMethods() {
+		Set<HttpMethod> supportedMethods = new HashSet<HttpMethod>();
+		for (String value : this.supportedMethods) {
+			supportedMethods.add(HttpMethod.valueOf(value));
+		}
+		return supportedMethods;
+	}
+
 }

spring-web/src/main/java/org/springframework/web/bind/annotation/ControllerAdvice.java

@@ -32,7 +32,7 @@ import org.springframework.stereotype.Component;
  *
  * <p>It is typically used to define {@link ExceptionHandler @ExceptionHandler},
  * {@link InitBinder @InitBinder}, and {@link ModelAttribute @ModelAttribute}
- * methods that apply across controller class hierarchies.
+ * methods that apply to all {@link RequestMapping @RequestMapping} methods.
  *
  * @author Rossen Stoyanchev
  * @since 3.2