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

Includes consistent use of getContentLengthLong over getContentLength.

Issue: SPR-17320

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

@@ -19,7 +19,6 @@
 import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.IOException;
-import java.io.InputStream;
 import java.net.HttpURLConnection;
 import java.net.URI;
 import java.net.URL;
@@ -66,18 +65,17 @@ else if (code == HttpURLConnection.HTTP_NOT_FOUND) {
 						return false;
 					}
 				}
-				if (con.getContentLength() >= 0) {
+				if (con.getContentLengthLong() >= 0) {
 					return true;
 				}
 				if (httpCon != null) {
-					// no HTTP OK status, and no content-length header: give up
+					// No HTTP OK status, and no content-length header: give up
 					httpCon.disconnect();
 					return false;
 				}
 				else {
 					// Fall back to stream existence: can we open the stream?
-					InputStream is = getInputStream();
-					is.close();
+					getInputStream().close();
 					return true;
 				}
 			}
@@ -211,7 +209,7 @@ public long contentLength() throws IOException {
 			// Try a URL connection content-length header
 			URLConnection con = url.openConnection();
 			customizeConnection(con);
-			return con.getContentLength();
+			return con.getContentLengthLong();
 		}
 	}
 

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.
@@ -57,8 +57,7 @@ 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) {
@@ -146,7 +145,7 @@ public long contentLength() throws IOException {
 		InputStream is = getInputStream();
 		try {
 			long size = 0;
-			byte[] buf = new byte[255];
+			byte[] buf = new byte[256];
 			int read;
 			while ((read = is.read(buf)) != -1) {
 				size += read;
@@ -169,10 +168,11 @@ 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;
 	}