Allow file locations for resource handling

Prior to this change, location checks for serving resources would append
`/` to the location path it didn't already have one.

This commit makes sure not to append a `/` if the provided location is
actually a file.

Issue: SPR-12747

Author: bclozel

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

@@ -179,6 +179,9 @@ else if (resource instanceof ServletContextResource) {
 			resourcePath = resource.getURL().getPath();
 			locationPath = StringUtils.cleanPath(location.getURL().getPath());
 		}
+		if(locationPath.equals(resourcePath)) {
+			return true;
+		}
 		locationPath = (locationPath.endsWith("/") || locationPath.isEmpty() ? locationPath : locationPath + "/");
 		if (!resourcePath.startsWith(locationPath)) {
 			return false;

spring-webmvc/src/test/java/org/springframework/web/servlet/resource/PathResourceResolverTests.java

@@ -117,4 +117,11 @@ public void checkRelativeLocation() throws Exception {
 		assertNotNull(this.resolver.resolveResource(null, "main.css", Arrays.asList(location), null));
 	}
 
+	// SPR-12747
+	@Test
+	public void checkFileLocation() throws Exception {
+		Resource resource = new ClassPathResource("test/main.css", PathResourceResolver.class);
+		assertTrue(this.resolver.checkResource(resource, resource));
+	}
+
 }