Fixes failing tests

Author: aaronzi

basyx.common/basyx.filerepository-backend/src/main/java/org/eclipse/digitaltwin/basyx/core/filerepository/FileRepositoryHelper.java

@@ -52,9 +52,10 @@ private FileRepositoryHelper() {
     /**
      * Retrieves repository content and materializes it as a temporary local file.
      * <p>
-     * The repository id is never used as a filesystem path. The caller owns the
-     * returned temporary file and is responsible for deleting it when it is no
-     * longer needed.
+     * The repository id is never used as a filesystem path. A conservative file
+     * extension is preserved for compatibility with callers that inspect the
+     * returned file name. The caller owns the returned temporary file and is
+     * responsible for deleting it when it is no longer needed.
      *
      * @param fileRepository
      *            the file repository instance
@@ -68,7 +69,7 @@ public static File fetchAndStoreFileLocally(FileRepository fileRepository, Strin
         Path temporaryFile = null;
 
         try (InputStream fileIs = fileRepository.find(filePath)) {
-            temporaryFile = Files.createTempFile("basyx-file-", ".tmp");
+            temporaryFile = Files.createTempFile("basyx-file-", getSafeTempFileSuffix(filePath));
             Files.copy(fileIs, temporaryFile, StandardCopyOption.REPLACE_EXISTING);
             return temporaryFile.toFile();
         } catch (IOException e) {
@@ -211,6 +212,9 @@ private static String createUniqueFileName(String logicalFileName) {
     }
 
     private static String getFileExtension(String fileName) {
+        if (fileName == null)
+            return "";
+
         int extensionStart = fileName.lastIndexOf('.');
 
         if (extensionStart <= 0 || extensionStart >= fileName.length() - 1)
@@ -224,6 +228,15 @@ private static String getFileExtension(String fileName) {
         return "." + extension;
     }
 
+    private static String getSafeTempFileSuffix(String filePath) {
+        String extension = getFileExtension(filePath);
+
+        if (extension.isEmpty())
+            return ".tmp";
+
+        return extension;
+    }
+
     private static boolean isAsciiLetterOrDigit(int character) {
         return character >= 'a' && character <= 'z' || character >= 'A' && character <= 'Z' || character >= '0' && character <= '9';
     }

basyx.common/basyx.filerepository-backend/src/test/java/org/eclipse/digitaltwin/basyx/core/filerepository/FileRepositoryHelperTest.java

@@ -115,6 +115,7 @@ public void fetchAndStoreFileLocallyDoesNotUseRepositoryKeyAsFilesystemPath() th
 			java.io.File localFile = FileRepositoryHelper.fetchAndStoreFileLocally(fileRepository, maliciousRepositoryKey);
 
 			assertTrue(localFile.exists());
+			assertTrue(localFile.getName().endsWith(".txt"));
 			assertNotEquals(victimFile.toAbsolutePath().toString(), localFile.toPath().toAbsolutePath().toString());
 			assertFalse(Files.exists(victimFile));
 			assertArrayEquals(attackerPayload, Files.readAllBytes(localFile.toPath()));