TSK-407: supporting all kind of lists for transferring tasks.

lib/taskana-core/src/main/java/pro/taskana/impl/TaskServiceImpl.java

@@ -484,9 +484,10 @@ public class TaskServiceImpl implements TaskService {
             taskanaEngine.openConnection();
             LOGGER.debug("entry to transferBulk(targetWbId = {}, taskIds = {})", destinationWorkbasketId, taskIds);
             // Check pre-conditions with trowing Exceptions
-            if (destinationWorkbasketId == null || taskIds == null) {
+            if (destinationWorkbasketId == null || destinationWorkbasketId.isEmpty() || taskIds == null
+                || taskIds.isEmpty()) {
                 throw new InvalidArgumentException(
-                    "DestinationWorkbasketId or TaskIds can´t be used as NULL-Parameter.");
+                    "DestinationWorkbasketId or TaskIds must not be null or empty.");
             }
             Workbasket destinationWorkbasket = workbasketService.getWorkbasket(destinationWorkbasketId);
 
@@ -521,10 +522,18 @@ public class TaskServiceImpl implements TaskService {
         }
     }
 
-    private BulkOperationResults<String, TaskanaException> transferTasks(List<String> taskIds,
+    private BulkOperationResults<String, TaskanaException> transferTasks(List<String> taskIdsToBeTransferred,
         Workbasket destinationWorkbasket) throws InvalidArgumentException {
         BulkOperationResults<String, TaskanaException> bulkLog = new BulkOperationResults<>();
 
+        // convert to ArrayList<String> if necessary to prevent a UnsupportedOperationException while removing
+        ArrayList<String> taskIds;
+        if (!(taskIdsToBeTransferred instanceof ArrayList)) {
+            taskIds = new ArrayList<>(taskIdsToBeTransferred);
+        } else {
+            taskIds = (ArrayList<String>) taskIdsToBeTransferred;
+        }
+
         // check tasks Ids exist and not empty - log and remove
         Iterator<String> taskIdIterator = taskIds.iterator();
         while (taskIdIterator.hasNext()) {

lib/taskana-core/src/test/java/acceptance/task/TransferTaskAccTest.java

@@ -12,6 +12,8 @@ import static org.junit.Assert.fail;
 import java.sql.SQLException;
 import java.time.Instant;
 import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -251,4 +253,32 @@ public class TransferTaskAccTest extends AbstractAccTest {
         assertEquals("TEAMLEAD_1", transferredTask.getWorkbasketKey());
     }
 
+    @WithAccessId(
+        userName = "teamlead_1",
+        groupNames = {"group_1"})
+    @Test
+    public void testTransferTasksWithListNotSupportingRemove()
+        throws SQLException, NotAuthorizedException, InvalidArgumentException, ClassificationNotFoundException,
+        WorkbasketNotFoundException, TaskAlreadyExistException, InvalidWorkbasketException, TaskNotFoundException,
+        InvalidStateException, InvalidOwnerException {
+        TaskService taskService = taskanaEngine.getTaskService();
+        List<String> taskIds = Collections.singletonList("");
+        taskService.transferTasks("WBI:100000000000000000000000000000000006", taskIds);
+
+    }
+
+    @WithAccessId(
+        userName = "teamlead_1",
+        groupNames = {"group_1"})
+    @Test(expected = InvalidArgumentException.class)
+    public void testThrowsExceptionIfEmptyListIsSupplied()
+        throws SQLException, NotAuthorizedException, InvalidArgumentException, ClassificationNotFoundException,
+        WorkbasketNotFoundException, TaskAlreadyExistException, InvalidWorkbasketException, TaskNotFoundException,
+        InvalidStateException, InvalidOwnerException {
+        TaskService taskService = taskanaEngine.getTaskService();
+        List<String> taskIds = new ArrayList<>();
+        taskService.transferTasks("WBI:100000000000000000000000000000000006", taskIds);
+
+    }
+
 }