Merge pull request #12894 from jkschneider:webmvc-tags-perf

* pr/12894:
  Polish "Less object instantiation in WebMvcTags"
  Less object instantiation in WebMvcTags

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/metrics/web/servlet/WebMvcTags.java

@@ -40,6 +40,14 @@ public final class WebMvcTags {
 
 	private static final Tag URI_REDIRECTION = Tag.of("uri", "REDIRECTION");
 
+	private static final Tag URI_UNKNOWN = Tag.of("uri", "UNKNOWN");
+
+	private static final Tag EXCEPTION_NONE = Tag.of("exception", "None");
+
+	private static final Tag STATUS_UNKNOWN = Tag.of("status", "UNKNOWN");
+
+	private static final Tag METHOD_UNKNOWN = Tag.of("method", "UNKNOWN");
+
 	private WebMvcTags() {
 	}
 
@@ -50,8 +58,7 @@ public final class WebMvcTags {
 	 * @return the method tag whose value is a capitalized method (e.g. GET).
 	 */
 	public static Tag method(HttpServletRequest request) {
-		return (request == null ? Tag.of("method", "UNKNOWN")
-				: Tag.of("method", request.getMethod()));
+		return (request == null ? METHOD_UNKNOWN : Tag.of("method", request.getMethod()));
 	}
 
 	/**
@@ -60,8 +67,8 @@ public final class WebMvcTags {
 	 * @return the status tag derived from the status of the response
 	 */
 	public static Tag status(HttpServletResponse response) {
-		return (response == null ? Tag.of("status", "UNKNOWN")
-				: Tag.of("status", ((Integer) response.getStatus()).toString()));
+		return (response == null ? STATUS_UNKNOWN :
+				Tag.of("status", Integer.toString(response.getStatus())));
 	}
 
 	/**
@@ -91,7 +98,7 @@ public final class WebMvcTags {
 			String pathInfo = getPathInfo(request);
 			return Tag.of("uri", pathInfo.isEmpty() ? "root" : pathInfo);
 		}
-		return Tag.of("uri", "UNKNOWN");
+		return URI_UNKNOWN;
 	}
 
 	private static HttpStatus extractStatus(HttpServletResponse response) {
@@ -121,8 +128,9 @@ public final class WebMvcTags {
 	 * @return the exception tag derived from the exception
 	 */
 	public static Tag exception(Throwable exception) {
-		return Tag.of("exception",
-				(exception == null ? "None" : exception.getClass().getSimpleName()));
+		return (exception != null
+				? Tag.of("exception", exception.getClass().getSimpleName())
+				: EXCEPTION_NONE);
 	}
 
 }