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);
 				}
 

spring-web/src/test/java/org/springframework/web/util/Log4jWebConfigurerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2011 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.
@@ -37,8 +37,9 @@ import org.springframework.mock.web.MockServletContext;
 public class Log4jWebConfigurerTests {
 
 	private static final String TESTLOG4J_PROPERTIES = "testlog4j.properties";
-	private static final String CLASSPATH_RESOURCE = "classpath:org/springframework/web/util/testlog4j.properties";
-	private static final String RELATIVE_PATH = "src/test/resources/org/springframework/web/util/testlog4j.properties";
+	private static final String PROPERTIES_LOCATION = "org/springframework/web/util/testlog4j.properties";
+	private static final String CLASSPATH_RESOURCE = "classpath:" + PROPERTIES_LOCATION;
+	private static final String RELATIVE_PATH = "src/test/resources/" + PROPERTIES_LOCATION;
 
 	@Test
 	public void initLoggingWithClasspathResource() {
@@ -59,7 +60,12 @@ public class Log4jWebConfigurerTests {
 	public void initLoggingWithRelativeFilePathAndRefreshInterval() {
 		initLogging(RELATIVE_PATH, true);
 	}
-	
+
+	@Test // See SPR-9417
+	public void initLoggingWithPlaceholderResolvingToValidUrl() {
+		initLogging("${some.prop.name:classpath:}" + PROPERTIES_LOCATION, true);
+	}
+
 	@Test
 	public void initLoggingWithUrl() {
 		URL url = Log4jWebConfigurerTests.class.getResource(TESTLOG4J_PROPERTIES);