Fix property replacement bug in Log4jWebConfigurer

Previously, if the resolution of a ${...} placeholder resulted in a
valid URL for the location of a log4j properties/XML file, the URL
would ultimately be malformed by an unnecessary call to to
WebUtils#getRealPath.

The implementation of Log4jWebConfigurer#initLogging now eagerly
attempts SystemPropertyUtils#resolvePlaceholders before checking to see
if the location is a valid URL, and bypassing the call to
WebUtils#getRealPath if so.

Issue: SPR-9417

spring-web/src/main/java/org/springframework/web/util/Log4jWebConfigurer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2008 the original author or authors.
+ * Copyright 2002-2012 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.
@@ -124,9 +124,9 @@ public abstract class Log4jWebConfigurer {
 			try {
 				// Return a URL (e.g. "classpath:" or "file:") as-is;
 				// consider a plain file path as relative to the web application root directory.
+				location = SystemPropertyUtils.resolvePlaceholders(location);
 				if (!ResourceUtils.isUrl(location)) {
 					// Resolve system property placeholders before resolving real path.
-					location = SystemPropertyUtils.resolvePlaceholders(location);
 					location = WebUtils.getRealPath(servletContext, location);
 				}