Development: Modernize Java server code

src/main/java/de/tum/cit/aet/artemis/athena/service/AthenaRepositoryExportService.java

@@ -2,7 +2,6 @@
 
 import static de.tum.cit.aet.artemis.core.config.Constants.PROFILE_ATHENA;
 
-import java.io.File;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -79,11 +78,11 @@ private void checkFeedbackSuggestionsOrAutomaticFeedbackEnabledElseThrow(Exercis
      * @param exerciseId     the id of the exercise to export the repository for
      * @param submissionId   the id of the submission to export the repository for (only for student repository, otherwise pass null)
      * @param repositoryType the type of repository to export. Pass null to export the student repository.
-     * @return the zip file containing the exported repository
+     * @return the path to the zip file containing the exported repository
      * @throws IOException              if the export fails
      * @throws AccessForbiddenException if the feedback suggestions are not enabled for the given exercise
      */
-    public File exportRepository(long exerciseId, Long submissionId, RepositoryType repositoryType) throws IOException {
+    public Path exportRepository(long exerciseId, Long submissionId, RepositoryType repositoryType) throws IOException {
         log.debug("Exporting repository for exercise {}, submission {}", exerciseId, submissionId);
 
         var programmingExercise = programmingExerciseRepository.findByIdElseThrow(exerciseId);
@@ -97,27 +96,27 @@ public File exportRepository(long exerciseId, Long submissionId, RepositoryType
         }
 
         Path exportDir = fileService.getTemporaryUniqueSubfolderPath(repoDownloadClonePath, 15);
-        Path zipFile = null;
+        Path zipFilePath = null;
 
         if (repositoryType == null) { // Export student repository
             var submission = programmingSubmissionRepository.findById(submissionId).orElseThrow();
             // Load participation with eager submissions
             var participation = programmingExerciseStudentParticipationRepository.findWithSubmissionsById(submission.getParticipation().getId()).getFirst();
-            zipFile = programmingExerciseExportService.getRepositoryWithParticipation(programmingExercise, participation, exportOptions, exportDir, exportDir, true);
+            zipFilePath = programmingExerciseExportService.getRepositoryWithParticipation(programmingExercise, participation, exportOptions, exportDir, exportDir, true);
         }
         else {
             List<String> exportErrors = List.of();
             var exportFile = programmingExerciseExportService.exportInstructorRepositoryForExercise(programmingExercise.getId(), repositoryType, exportDir, exportDir,
                     exportErrors);
             if (exportFile.isPresent()) {
-                zipFile = exportFile.get().toPath();
+                zipFilePath = exportFile.get().toPath();
             }
         }
 
-        if (zipFile == null) {
+        if (zipFilePath == null) {
             throw new IOException("Failed to export repository");
         }
 
-        return zipFile.toFile();
+        return zipFilePath;
     }
 }

src/main/java/de/tum/cit/aet/artemis/buildagent/service/BuildAgentDockerService.java

@@ -2,7 +2,8 @@
 
 import static de.tum.cit.aet.artemis.core.config.Constants.PROFILE_BUILDAGENT;
 
-import java.io.File;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.time.Duration;
 import java.time.Instant;
 import java.time.ZonedDateTime;
@@ -353,8 +354,8 @@ public void checkUsableDiskSpaceThenCleanUp() {
 
         try {
             // Get the Docker root directory to check disk space.
-            File dockerRootDirectory = new File(Objects.requireNonNullElse(dockerClient.infoCmd().exec().getDockerRootDir(), "/"));
-            long usableSpace = dockerRootDirectory.getUsableSpace();
+            Path dockerRootDirectory = Path.of(Objects.requireNonNullElse(dockerClient.infoCmd().exec().getDockerRootDir(), "/"));
+            long usableSpace = Files.getFileStore(dockerRootDirectory).getUsableSpace();
 
             long threshold = convertMegabytesToBytes(imageCleanupDiskSpaceThresholdMb);
 
@@ -385,7 +386,7 @@ public void checkUsableDiskSpaceThenCleanUp() {
                     log.info("Remove oldest docker image {} to cleanup disk space to avoid filling up the hard disk", oldestImage.getKey());
                     try {
                         dockerClient.removeImageCmd(oldestImage.getKey()).exec();
-                        usableSpace = dockerRootDirectory.getUsableSpace();
+                        usableSpace = Files.getFileStore(dockerRootDirectory).getUsableSpace();
                         deleteAttempts--;
                     }
                     catch (NotFoundException e) {

src/main/java/de/tum/cit/aet/artemis/buildagent/service/BuildJobContainerService.java

@@ -5,11 +5,10 @@
 
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
-import java.io.File;
-import java.io.FileInputStream;
 import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.Files;
 import java.nio.file.Path;
-import java.nio.file.Paths;
 import java.time.ZonedDateTime;
 import java.util.ArrayList;
 import java.util.List;
@@ -18,6 +17,7 @@
 import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
+import java.util.stream.Stream;
 
 import org.apache.commons.compress.archivers.tar.TarArchiveEntry;
 import org.apache.commons.compress.archivers.tar.TarArchiveInputStream;
@@ -349,7 +349,7 @@ private void createScriptFile(String buildJobContainerId) {
     }
 
     private void addAndPrepareDirectoryAndReplaceContent(String containerId, Path repositoryPath, String newDirectoryName) {
-        copyToContainer(repositoryPath.toString(), containerId);
+        copyToContainer(repositoryPath, containerId);
         addDirectory(containerId, newDirectoryName, true);
         insertRepositoryFiles(containerId, LOCALCI_WORKING_DIRECTORY + "/" + repositoryPath.getFileName().toString(), newDirectoryName);
     }
@@ -363,7 +363,7 @@ private void addDirectory(String containerId, String directoryName, boolean crea
         executeDockerCommand(containerId, null, false, false, true, command);
     }
 
-    private void copyToContainer(String sourcePath, String containerId) {
+    private void copyToContainer(Path sourcePath, String containerId) {
         try (final var uploadStream = new ByteArrayInputStream(createTarArchive(sourcePath).toByteArray());
                 final var copyToContainerCommand = buildAgentConfiguration.getDockerClient().copyArchiveToContainerCmd(containerId).withRemotePath(LOCALCI_WORKING_DIRECTORY)
                         .withTarInputStream(uploadStream)) {
@@ -374,8 +374,7 @@ private void copyToContainer(String sourcePath, String containerId) {
         }
     }
 
-    private ByteArrayOutputStream createTarArchive(String sourcePath) {
-        Path path = Paths.get(sourcePath);
+    private ByteArrayOutputStream createTarArchive(Path sourcePath) {
 
         ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
 
@@ -385,37 +384,37 @@ private ByteArrayOutputStream createTarArchive(String sourcePath) {
         tarArchiveOutputStream.setLongFileMode(TarArchiveOutputStream.LONGFILE_POSIX);
 
         try {
-            addFileToTar(tarArchiveOutputStream, path.toFile(), "");
+            addFileToTar(tarArchiveOutputStream, sourcePath, "");
         }
         catch (IOException e) {
             throw new LocalCIException("Could not create tar archive", e);
         }
         return byteArrayOutputStream;
     }
 
-    private void addFileToTar(TarArchiveOutputStream tarArchiveOutputStream, File file, String parent) throws IOException {
-        TarArchiveEntry tarEntry = new TarArchiveEntry(file, parent + file.getName());
+    private void addFileToTar(TarArchiveOutputStream tarArchiveOutputStream, Path path, String parent) throws IOException {
+        TarArchiveEntry tarEntry = new TarArchiveEntry(path, parent + path.getFileName());
         tarArchiveOutputStream.putArchiveEntry(tarEntry);
 
-        if (file.isFile()) {
-            try (FileInputStream fis = new FileInputStream(file)) {
+        if (Files.isRegularFile(path)) {
+            try (InputStream is = Files.newInputStream(path)) {
                 byte[] buffer = new byte[1024];
                 int count;
-                while ((count = fis.read(buffer)) != -1) {
+                while ((count = is.read(buffer)) != -1) {
                     tarArchiveOutputStream.write(buffer, 0, count);
                 }
             }
             tarArchiveOutputStream.closeArchiveEntry();
         }
         else {
             tarArchiveOutputStream.closeArchiveEntry();
-            File[] children = file.listFiles();
-            if (children != null) {
-                for (File child : children) {
-                    addFileToTar(tarArchiveOutputStream, child, parent + file.getName() + "/");
+            try (Stream<Path> children = Files.list(path)) {
+                for (Path child : children.toList()) {
+                    addFileToTar(tarArchiveOutputStream, child, parent + path.getFileName() + "/");
                 }
             }
         }
+
     }
 
     private void executeDockerCommandWithoutAwaitingResponse(String containerId, String... command) {

src/main/java/de/tum/cit/aet/artemis/buildagent/service/BuildJobExecutionService.java

@@ -11,7 +11,6 @@
 import java.nio.file.DirectoryStream;
 import java.nio.file.Files;
 import java.nio.file.Path;
-import java.nio.file.Paths;
 import java.time.Duration;
 import java.time.ZonedDateTime;
 import java.util.ArrayList;
@@ -578,7 +577,7 @@ private Path cloneRepository(VcsRepositoryUri repositoryUri, @Nullable String co
     private void deleteCloneRepo(VcsRepositoryUri repositoryUri, @Nullable String commitHash, String buildJobId, Path repositoryPath) {
         String msg;
         try {
-            Path repositoryPathForDeletion = commitHash != null ? Paths.get(CHECKED_OUT_REPOS_TEMP_DIR, commitHash, repositoryUri.folderNameForRepositoryUri()) : repositoryPath;
+            Path repositoryPathForDeletion = commitHash != null ? Path.of(CHECKED_OUT_REPOS_TEMP_DIR, commitHash, repositoryUri.folderNameForRepositoryUri()) : repositoryPath;
             Repository repository = buildJobGitService.getExistingCheckedOutRepositoryByLocalPath(repositoryPathForDeletion, repositoryUri, defaultBranch);
             if (repository == null) {
                 msg = "Repository with commit hash " + commitHash + " not found";

src/main/java/de/tum/cit/aet/artemis/core/config/SAML2Configuration.java

@@ -1,11 +1,10 @@
 package de.tum.cit.aet.artemis.core.config;
 
-import java.io.File;
-import java.io.FileInputStream;
-import java.io.FileReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.security.Security;
 import java.security.cert.CertificateException;
 import java.security.cert.CertificateFactory;
@@ -117,27 +116,27 @@ private boolean checkFiles(SAML2Properties.RelyingPartyProperties config) {
             return false;
         }
 
-        File keyFile = new File(config.getKeyFile());
-        File certFile = new File(config.getCertFile());
+        Path keyFile = Path.of(config.getKeyFile());
+        Path certFile = Path.of(config.getCertFile());
 
-        if (!keyFile.exists() || !certFile.exists()) {
+        if (!Files.exists(keyFile) || !Files.exists(certFile)) {
             log.error("Keyfile or Certfile for SAML[{}] does not exist.", config.getRegistrationId());
             return false;
         }
 
         return true;
     }
 
-    private static X509Certificate readPublicCert(String file) throws IOException, CertificateException {
-        try (InputStream inStream = new FileInputStream(file)) {
+    private static X509Certificate readPublicCert(String filepath) throws IOException, CertificateException {
+        try (InputStream inStream = Files.newInputStream(Path.of(filepath))) {
             CertificateFactory cf = CertificateFactory.getInstance("X.509");
             return (X509Certificate) cf.generateCertificate(inStream);
         }
     }
 
-    private RSAPrivateKey readPrivateKey(String file) throws IOException {
+    private RSAPrivateKey readPrivateKey(String filepath) throws IOException {
         // Read PKCS#8 File!
-        try (var keyReader = new FileReader(file, StandardCharsets.UTF_8); var pemParser = new PEMParser(keyReader)) {
+        try (var keyReader = Files.newBufferedReader(Path.of(filepath), StandardCharsets.UTF_8); var pemParser = new PEMParser(keyReader)) {
             JcaPEMKeyConverter converter = new JcaPEMKeyConverter();
             PrivateKeyInfo privateKeyInfo = PrivateKeyInfo.getInstance(pemParser.readObject());
             return (RSAPrivateKey) converter.getPrivateKey(privateKeyInfo);

src/main/java/de/tum/cit/aet/artemis/core/config/WebConfigurer.java

@@ -3,8 +3,8 @@
 import static de.tum.cit.aet.artemis.core.config.Constants.PROFILE_CORE;
 import static java.net.URLDecoder.decode;
 
-import java.io.File;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.EnumSet;
 
@@ -96,9 +96,9 @@ private void setMimeMappings(WebServerFactory server) {
     private void setLocationForStaticAssets(WebServerFactory server) {
         if (server instanceof ConfigurableServletWebServerFactory servletWebServer) {
             String prefixPath = resolvePathPrefix();
-            File root = new File(prefixPath + "build/resources/main/static/");
-            if (root.exists() && root.isDirectory()) {
-                servletWebServer.setDocumentRoot(root);
+            Path root = Path.of(prefixPath + "build/resources/main/static/");
+            if (Files.exists(root) && Files.isDirectory(root)) {
+                servletWebServer.setDocumentRoot(root.toFile());
             }
         }
     }

src/main/java/de/tum/cit/aet/artemis/core/service/FileService.java

@@ -3,14 +3,9 @@
 import static de.tum.cit.aet.artemis.core.config.Constants.PROFILE_CORE;
 import static java.nio.charset.StandardCharsets.UTF_8;
 
-import java.io.BufferedReader;
-import java.io.BufferedWriter;
 import java.io.ByteArrayOutputStream;
 import java.io.File;
-import java.io.FileInputStream;
 import java.io.FileNotFoundException;
-import java.io.FileReader;
-import java.io.FileWriter;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
@@ -501,12 +496,11 @@
      * @throws IOException if the directory could not be renamed.
      */
     public void renameDirectory(Path oldDirectoryPath, Path targetDirectoryPath) throws IOException {
-        File oldDirectory = oldDirectoryPath.toFile();
-        if (!oldDirectory.exists()) {
-            log.error("Directory {} should be renamed but does not exist.", oldDirectoryPath);
-            throw new RuntimeException("Directory " + oldDirectoryPath + " should be renamed but does not exist.");
-        }
 
+        if (!Files.exists(oldDirectoryPath)) {
+            throw new FilePathParsingException("Directory " + oldDirectoryPath + " should be renamed but does not exist.");
+        }
+        File oldDirectory = oldDirectoryPath.toFile();
         File targetDirectory = targetDirectoryPath.toFile();
 
         FileUtils.moveDirectory(oldDirectory, targetDirectory);
@@ -521,12 +515,12 @@
     public void replacePlaceholderSections(Path filePath, Map<String, Boolean> sections) {
         Map<Pattern, Boolean> patternBooleanMap = sections.entrySet().stream().collect(Collectors.toMap(e -> Pattern.compile(".*%" + e.getKey() + ".*%.*"), Map.Entry::getValue));
         File file = filePath.toFile();
-        File tempFile = new File(filePath + "_temp");
+        File tempFile = Path.of(filePath + "_temp").toFile();
         if (!file.exists()) {
             throw new FilePathParsingException("File " + filePath + " should be updated but does not exist.");
         }
 
-        try (var reader = new BufferedReader(new FileReader(file, UTF_8)); var writer = new BufferedWriter(new FileWriter(tempFile, UTF_8))) {
+        try (var reader = Files.newBufferedReader(file.toPath(), UTF_8); var writer = Files.newBufferedWriter(tempFile.toPath(), UTF_8)) {
             Map.Entry<Pattern, Boolean> matchingStartPattern = null;
             String line = reader.readLine();
             while (line != null) {
@@ -599,12 +593,13 @@
         if (pathString.contains(targetString)) {
             log.debug("Target String found, replacing..");
             String targetPath = pathString.replace(targetString, replacementString);
-            renameDirectory(startPath, Path.of(targetPath));
-            directory = new File(targetPath);
+            final var path = Path.of(targetPath);
+            renameDirectory(startPath, path);
+            directory = path.toFile();
         }
 
         // Get all subdirectories
-        final var subDirectories = directory.list((current, name) -> new File(current, name).isDirectory());
+        final var subDirectories = directory.list((current, name) -> current.toPath().resolve(name).toFile().isDirectory());
 
         if (subDirectories != null) {
             for (String subDirectory : subDirectories) {
@@ -634,7 +629,7 @@
                 try {
                     // We expect the strings to be clean already, so the filename shouldn't change. If it does, we are on the safe side with the sanitation.
                     String cleanFileName = sanitizeFilename(filePath.toString().replace(targetString, replacementString));
-                    FileUtils.moveFile(filePath.toFile(), new File(cleanFileName));
+                    FileUtils.moveFile(filePath.toFile(), Path.of(cleanFileName).toFile());
                 }
                 catch (IOException e) {
                     throw new RuntimeException("File " + filePath + " should be replaced but does not exist.");
@@ -672,7 +667,7 @@
         }
 
         // Get all files in directory
-        String[] files = directory.list((current, name) -> new File(current, name).isFile());
+        String[] files = directory.list((current, name) -> current.toPath().resolve(name).toFile().isFile());
         if (files != null) {
             // filter out files that should be ignored
             files = Arrays.stream(files).filter(Predicate.not(filesToIgnore::contains)).toArray(String[]::new);
@@ -682,7 +677,7 @@
         }
 
         // Recursive call: get all subdirectories
-        String[] subDirectories = directory.list((current, name) -> new File(current, name).isDirectory());
+        String[] subDirectories = directory.list((current, name) -> current.toPath().resolve(name).toFile().isDirectory());
         if (subDirectories != null) {
             for (String subDirectory : subDirectories) {
                 if (subDirectory.equalsIgnoreCase(".git")) {
@@ -1040,7 +1035,7 @@
             FileItem fileItem = new DiskFileItem(cleanFilename, Files.probeContentType(tempPath), false, outputFile.getName(), (int) outputFile.length(),
                     outputFile.getParentFile());
 
-            try (InputStream input = new FileInputStream(outputFile); OutputStream fileItemOutputStream = fileItem.getOutputStream()) {
+            try (InputStream input = Files.newInputStream(outputFile.toPath()); OutputStream fileItemOutputStream = fileItem.getOutputStream()) {
                 IOUtils.copy(input, fileItemOutputStream);
             }
             return new CommonsMultipartFile(fileItem);

src/main/java/de/tum/cit/aet/artemis/core/service/ResourceLoaderService.java

@@ -9,7 +9,6 @@
 import java.net.URL;
 import java.nio.file.Files;
 import java.nio.file.Path;
-import java.nio.file.Paths;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Objects;
@@ -216,7 +215,7 @@ public Path getResourceFilePath(Path path) throws IOException, URISyntaxExceptio
 
         if ("file".equals(resourceUrl.getProtocol())) {
             // Resource is in the file system.
-            return Paths.get(resourceUrl.toURI());
+            return Path.of(resourceUrl.toURI());
         }
         else if ("jar".equals(resourceUrl.getProtocol())) {
             // Resource is in a jar file.