Ensure PathResourceResolvers log warnings for non-existent resources

Prior to this commit, the getResource() methods in PathResourceResolver
implementations allowed an exception thrown from Resource#getURL() to
propagate instead of logging a warning about the missing resource as
intended.

This commit modifies the getResource() methods in PathResourceResolver
implementations so that the log messages include the output of the
toString() implementations of the underlying resources instead of their
getURL() implementations, which may throw an exception.

Furthermore, logging the toString() output of resources aligns with the
existing output for "allowed locations" in the same log message.

Note that the toString() implementations could potentially also throw
exceptions, but that is considered less likely.

Closes gh-31623

spring-webflux/src/main/java/org/springframework/web/reactive/resource/PathResourceResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -123,8 +123,8 @@ else if (logger.isWarnEnabled()) {
 					Resource[] allowed = getAllowedLocations();
 					logger.warn(LogFormatUtils.formatValue(
 							"Resource path \"" + resourcePath + "\" was successfully resolved " +
-									"but resource \"" + resource.getURL() + "\" is neither under the " +
-									"current location \"" + location.getURL() + "\" nor under any of the " +
+									"but resource \"" + resource + "\" is neither under the " +
+									"current location \"" + location + "\" nor under any of the " +
 									"allowed locations " + (allowed != null ? Arrays.asList(allowed) : "[]"), -1, true));
 				}
 			}

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/PathResourceResolver.java

@@ -195,8 +195,8 @@ else if (logger.isWarnEnabled()) {
 				Resource[] allowed = getAllowedLocations();
 				logger.warn(LogFormatUtils.formatValue(
 						"Resource path \"" + resourcePath + "\" was successfully resolved " +
-								"but resource \"" + resource.getURL() + "\" is neither under " +
-								"the current location \"" + location.getURL() + "\" nor under any of " +
+								"but resource \"" + resource + "\" is neither under " +
+								"the current location \"" + location + "\" nor under any of " +
 								"the allowed locations " + (allowed != null ? Arrays.asList(allowed) : "[]"), -1, true));
 			}
 		}