feat: upgrade to Java 21

build.gradle

@@ -65,10 +65,10 @@ dependencies {
 
 java {
     toolchain {
-        languageVersion.set(JavaLanguageVersion.of(17))
+        languageVersion.set(JavaLanguageVersion.of(21))
     }
-    sourceCompatibility = JavaVersion.VERSION_17
-    targetCompatibility = JavaVersion.VERSION_17
+    sourceCompatibility = JavaVersion.VERSION_21
+    targetCompatibility = JavaVersion.VERSION_21
     withJavadocJar()
     withSourcesJar()
 }

src/main/java/com/iexec/common/utils/FileHelper.java

@@ -29,7 +29,8 @@
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
-import java.net.URL;
+import java.io.InputStream;
+import java.net.URI;
 import java.nio.file.*;
 import java.nio.file.attribute.BasicFileAttributes;
 import java.util.Objects;
@@ -109,9 +110,10 @@ public static File createFileWithContent(String filePath, byte[] data) {
 
     /**
      * Download file with custom name in specified directory
-     * @param fileUrl URL of the file
+     *
+     * @param fileUrl          URL of the file
      * @param parentFolderPath directory path where the file will be downloaded
-     * @param outputFilename desired name for future downloaded file
+     * @param outputFilename   desired name for future downloaded file
      * @return downloaded file location path if successful download
      */
     public static String downloadFile(String fileUrl,
@@ -132,7 +134,7 @@ public static String downloadFile(String fileUrl,
             return "";
         }
         byte[] fileBytes = readFileBytesFromUrl(fileUrl);
-        if (fileBytes == null) {
+        if (fileBytes.length == 0) {
             log.error("Failed to download file [fileUrl:{}]", fileUrl);
             return "";
         }
@@ -158,23 +160,25 @@ public static String downloadFile(String fileUrl,
 
     /**
      * Read the content of the remote file located at the provided URL.
-     * @param url of the file
+     *
+     * @param uri URI of the file
      * @return the content of the file in a byte array if success,
-     * null otherwise.
+     * an empty byte array otherwise.
      */
-    public static byte[] readFileBytesFromUrl(String url) {
-        try {
-            return new URL(url).openStream().readAllBytes();
+    public static byte[] readFileBytesFromUrl(final String uri) {
+        try (final InputStream inputStream = new URI(uri).toURL().openStream()) {
+            return inputStream.readAllBytes();
         } catch (Exception e) {
-            log.error("Failed to read file bytes from url [url:{}]", url, e);
-            return null;
+            log.error("Failed to read file bytes from URI [uri:{}]", uri, e);
+            return new byte[0];
         }
     }
 
     /**
      * Download file and returns downloaded file location path if successful.
      * Downloaded file name is inferred from uri end path
-     * @param fileUri URI of the file
+     *
+     * @param fileUri               URI of the file
      * @param downloadDirectoryPath directory path where the file will be downloaded
      * @return downloaded file location path if successful download
      */

src/test/java/com/iexec/common/utils/FileHelperTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2020-2025 IEXEC BLOCKCHAIN TECH
+ * Copyright 2020-2026 IEXEC BLOCKCHAIN TECH
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -262,7 +262,7 @@ void shouldReadFileBytesFromUrl() {
     @Test
     void shouldNotReadFileBytesFromBadUrl() {
         byte[] bytes = FileHelper.readFileBytesFromUrl("http://bad-url");
-        assertThat(bytes).isNull();
+        assertThat(bytes).isEqualTo(new byte[0]);
     }
     // endregion