Resource.lastModified() propagates 0 value if target resource exists

Issue: SPR-17320

Author: jhoeller

spring-core/src/main/java/org/springframework/core/io/AbstractResource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -55,8 +55,7 @@ public boolean exists() {
 		catch (IOException ex) {
 			// Fall back to stream existence: can we open the stream?
 			try {
-				InputStream is = getInputStream();
-				is.close();
+				getInputStream().close();
 				return true;
 			}
 			catch (Throwable isEx) {
@@ -126,7 +125,7 @@ public long contentLength() throws IOException {
 		Assert.state(is != null, "Resource InputStream must not be null");
 		try {
 			long size = 0;
-			byte[] buf = new byte[255];
+			byte[] buf = new byte[256];
 			int read;
 			while ((read = is.read(buf)) != -1) {
 				size += read;
@@ -149,10 +148,11 @@ public long contentLength() throws IOException {
 	 */
 	@Override
 	public long lastModified() throws IOException {
-		long lastModified = getFileForLastModifiedCheck().lastModified();
-		if (lastModified == 0L) {
+		File fileToCheck = getFileForLastModifiedCheck();
+		long lastModified = fileToCheck.lastModified();
+		if (lastModified == 0L && !fileToCheck.exists()) {
 			throw new FileNotFoundException(getDescription() +
-					" cannot be resolved in the file system for resolving its last-modified timestamp");
+					" cannot be resolved in the file system for checking its last-modified timestamp");
 		}
 		return lastModified;
 	}