Add thread-safety when reading the bulkImportReport-files.

src/main/java/eu/openaire/urls_controller/controllers/BulkImportController.java

@@ -224,6 +224,8 @@ public class BulkImportController {
         // Write the contents of the report-file to a string (efficiently!) and return the whole content as an HTTP-response.
         final StringBuilder stringBuilder = new StringBuilder(25_000);
         String line;
+
+        FileUtils.fileAccessLock.lock();
         try ( BufferedReader in = new BufferedReader(new InputStreamReader(Files.newInputStream(Paths.get(this.bulkImportReportLocation, bulkImportReportId + ".json"))), FileUtils.twentyFiveKb) ) {
             while ( (line = in.readLine()) != null )
                 stringBuilder.append(line).append("\n");    // The "readLine()" does not return the line-term char.
@@ -234,6 +236,8 @@ public class BulkImportController {
             String errorMsg = "Failed to read the contents of report-file with ID: " + bulkImportReportId;
             logger.error(errorMsg, e);
             return ResponseEntity.internalServerError().body(errorMsg); // It's ok to give the file-path to the user, since the report already contains the file-path.
+        } finally {
+            FileUtils.fileAccessLock.unlock();
         }
 
         String json = stringBuilder.toString().trim();

src/main/java/eu/openaire/urls_controller/util/FileUtils.java

@@ -698,12 +698,12 @@ public class FileUtils {
     }
 
 
-    private static final Lock fileWriteLock = new ReentrantLock(true);
+    public static final Lock fileAccessLock = new ReentrantLock(true);
 
     public String writeToFile(String fileFullPath, String stringToWrite, boolean shouldLockThreads)
     {
         if ( shouldLockThreads )    // In case multiple threads write to the same file. for ex. during the bulk-import procedure.
-            fileWriteLock.lock();
+            fileAccessLock.lock();
 
         try ( BufferedWriter bufferedWriter = new BufferedWriter(Files.newBufferedWriter(Paths.get(fileFullPath)), halfMb) )
         {
@@ -714,7 +714,7 @@ public class FileUtils {
             return errorMsg;
         } finally {
             if ( shouldLockThreads )
-                fileWriteLock.unlock();
+                fileAccessLock.unlock();
         }
         return null;
     }