SPR-16838 PathMatchingResourcePatternResolver should enforce consistent

alphabetical sorting of directory content

A sort was added in SPR-14085 but the default File#compareTo depends
upon the underlying system.
The ordering of the ressources returned by
PathMatchingResourcePatternResolver#retrieveMatchingFiles may differ
between OS (Windows, Unix).
This leads to subtle bugs hard to track.
This PR replace the default sort with one based on the file name.

Author: benbenw

spring-core/src/main/java/org/springframework/core/io/support/PathMatchingResourcePatternResolver.java

@@ -790,7 +790,10 @@ protected void doRetrieveMatchingFiles(String fullPattern, File dir, Set<File> r
 			}
 			return;
 		}
-		Arrays.sort(dirContents);
+		
+		// enforce consistent alphabetical sorting to avoid different order between OS
+		Arrays.sort(dirContents, (f1, f2) -> f1.getName().compareTo(f2.getName()));
+		
 		for (File content : dirContents) {
 			String currPath = StringUtils.replace(content.getAbsolutePath(), File.separator, "/");
 			if (content.isDirectory() && getPathMatcher().matchStart(fullPattern, currPath + "/")) {

spring-core/src/test/java/org/springframework/core/io/support/PathMatchingResourcePatternResolverTests.java

@@ -16,15 +16,18 @@
 
 package org.springframework.core.io.support;
 
+import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Set;
 
 import org.junit.Ignore;
+import org.junit.Rule;
 import org.junit.Test;
-
+import org.junit.rules.TemporaryFolder;
 import org.springframework.core.io.Resource;
 import org.springframework.util.StringUtils;
 
@@ -56,6 +59,8 @@ public class PathMatchingResourcePatternResolverTests {
 
 	private PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
 
+	@Rule
+	public TemporaryFolder folder = new TemporaryFolder();
 
 	@Test(expected = FileNotFoundException.class)
 	public void invalidPrefixWithPatternElementInIt() throws IOException {
@@ -117,6 +122,27 @@ public void rootPatternRetrievalInJarFiles() throws IOException {
 		}
 		assertTrue("Could not find aspectj_1_5_0.dtd in the root of the aspectjweaver jar", found);
 	}
+	
+	
+	@Test
+	public void testConsistentFileOrder() throws IOException {
+		
+		List<String> expectedFileNames = new ArrayList<>();
+		
+		expectedFileNames.add(folder.newFile("A.txt").getName());
+		expectedFileNames.add(folder.newFile("B.txt").getName());
+		expectedFileNames.add(folder.newFile("P.txt").getName());
+		File newFolder = folder.newFolder("message");
+		expectedFileNames.add(File.createTempFile("Message", ".txt", newFolder).getName());
+		
+		Set<File> matchingFiles = resolver.retrieveMatchingFiles(folder.getRoot(), "**/*.txt");
+		assertEquals(expectedFileNames.size(), matchingFiles.size());
+		int i = 0;
+		for (File file : matchingFiles) {
+			assertEquals(expectedFileNames.get(i), file.getName());
+			i++;
+		}
+	}
 
 
 	private void assertProtocolAndFilenames(Resource[] resources, String protocol, String... filenames)