TSK-2013 selectAndClaim TasK return Optional and does not throw Exception if Task is notFound

lib/taskana-core/src/main/java/pro/taskana/task/api/TaskService.java

@@ -3,6 +3,7 @@ package pro.taskana.task.api;
 import java.time.Instant;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 
 import pro.taskana.classification.api.exceptions.ClassificationNotFoundException;
 import pro.taskana.classification.api.models.Classification;
@@ -190,7 +191,7 @@ public interface TaskService {
    * @throws NotAuthorizedOnWorkbasketException if the current user has no {@linkplain
    *     WorkbasketPermission#READ} for the {@linkplain Workbasket} the {@linkplain Task} is in
    */
-  Task selectAndClaim(TaskQuery taskQuery)
+  Optional<Task> selectAndClaim(TaskQuery taskQuery)
       throws InvalidOwnerException, NotAuthorizedOnWorkbasketException;
 
   /**

lib/taskana-core/src/main/java/pro/taskana/task/internal/TaskServiceImpl.java

@@ -1,6 +1,7 @@
 package pro.taskana.task.internal;
 
 import static java.util.function.Predicate.not;
+import static pro.taskana.common.internal.util.CheckedFunction.wrap;
 
 import java.time.Instant;
 import java.time.temporal.ChronoUnit;
@@ -581,30 +582,11 @@ public class TaskServiceImpl implements TaskService {
   }
 
   @Override
-  public Task selectAndClaim(TaskQuery taskQuery)
-      throws InvalidOwnerException, NotAuthorizedOnWorkbasketException {
-
-    try {
-
-      taskanaEngine.openConnection();
-
-      ((TaskQueryImpl) taskQuery).selectAndClaimEquals(true);
-
-      TaskSummary taskSummary = taskQuery.single();
-
-      if (taskSummary == null) {
-        throw new SystemException(
-            "No tasks matched the specified filter and sorting options,"
-                + " task query returned nothing!");
-      }
-
-      return claim(taskSummary.getId());
-
-    } catch (TaskNotFoundException | InvalidTaskStateException e) {
-      throw new SystemException("Caught exception ", e);
-    } finally {
-      taskanaEngine.returnConnection();
-    }
+  public Optional<Task> selectAndClaim(TaskQuery taskQuery) {
+    ((TaskQueryImpl) taskQuery).selectAndClaimEquals(true);
+    return taskanaEngine.executeInDatabaseConnection(
+        () ->
+            Optional.ofNullable(taskQuery.single()).map(TaskSummary::getId).map(wrap(this::claim)));
   }
 
   @Override

lib/taskana-core/src/test/java/acceptance/task/claim/SelectAndClaimTaskAccTest.java

@@ -1,23 +1,21 @@
 package acceptance.task.claim;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 import acceptance.AbstractAccTest;
 import java.security.PrivilegedAction;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Optional;
 import java.util.function.Consumer;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 import javax.security.auth.Subject;
-import org.assertj.core.api.ThrowableAssert.ThrowingCallable;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 
 import pro.taskana.common.api.BaseQuery.SortDirection;
-import pro.taskana.common.api.exceptions.SystemException;
 import pro.taskana.common.api.security.UserPrincipal;
 import pro.taskana.common.internal.util.CheckedConsumer;
 import pro.taskana.common.test.security.JaasExtension;
@@ -58,15 +56,11 @@ class SelectAndClaimTaskAccTest extends AbstractAccTest {
 
   @Test
   @WithAccessId(user = "admin")
-  void should_ThrowException_When_TryingToSelectAndClaimNonExistingTask() {
+  void should_ReturnEmptyOptional_When_TryingToSelectAndClaimNonExistingTask() throws Exception {
 
     TaskQuery query = taskanaEngine.getTaskService().createTaskQuery().idIn("notexisting");
-    ThrowingCallable call = () -> taskanaEngine.getTaskService().selectAndClaim(query);
-    assertThatThrownBy(call)
-        .isInstanceOf(SystemException.class)
-        .hasMessageContaining(
-            "No tasks matched the specified filter and sorting options, "
-                + "task query returned nothing!");
+    Optional<Task> task = taskanaEngine.getTaskService().selectAndClaim(query);
+    assertThat(task).isEmpty();
   }
 
   private Runnable getRunnableTest(List<Task> selectedAndClaimedTasks, List<String> accessIds) {
@@ -76,10 +70,10 @@ class SelectAndClaimTaskAccTest extends AbstractAccTest {
 
       Consumer<TaskService> consumer =
           CheckedConsumer.wrap(
-              taskService -> {
-                Task task = taskService.selectAndClaim(getTaskQuery());
-                selectedAndClaimedTasks.add(task);
-              });
+              taskService ->
+                  taskService
+                      .selectAndClaim(getTaskQuery())
+                      .ifPresent(selectedAndClaimedTasks::add));
       PrivilegedAction<Void> action =
           () -> {
             consumer.accept(taskanaEngine.getTaskService());

rest/taskana-rest-spring/src/main/java/pro/taskana/task/rest/TaskController.java

@@ -5,6 +5,7 @@ import static java.util.function.Predicate.not;
 import java.beans.ConstructorProperties;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Optional;
 import java.util.Set;
 import java.util.function.BiConsumer;
 import java.util.stream.Collectors;
@@ -233,7 +234,7 @@ public class TaskController {
    * @param filterCustomFields the filter parameters regarding TaskCustomFields
    * @param filterCustomIntFields the filter parameters regarding TaskCustomIntFields
    * @param sortParameter the sort parameters
-   * @return the claimed Task
+   * @return the claimed Task or 404 if no Task is found
    * @throws InvalidOwnerException if the Task is already claimed by someone else
    * @throws NotAuthorizedOnWorkbasketException if the current user has no read permission for the
    *     Workbasket the Task is in
@@ -254,9 +255,11 @@ public class TaskController {
     filterCustomIntFields.apply(query);
     sortParameter.apply(query);
 
-    Task selectedAndClaimedTask = taskService.selectAndClaim(query);
+    Optional<Task> selectedAndClaimedTask = taskService.selectAndClaim(query);
 
-    return ResponseEntity.ok(taskRepresentationModelAssembler.toModel(selectedAndClaimedTask));
+    return selectedAndClaimedTask
+        .map(task -> ResponseEntity.ok(taskRepresentationModelAssembler.toModel(task)))
+        .orElseGet(() -> ResponseEntity.notFound().build());
   }
 
   /**

rest/taskana-rest-spring/src/main/java/pro/taskana/task/rest/assembler/TaskRepresentationModelAssembler.java

@@ -51,7 +51,7 @@ public class TaskRepresentationModelAssembler
 
   @NonNull
   @Override
-  public TaskRepresentationModel toModel(@NonNull Task task) {
+  public TaskRepresentationModel toModel(Task task) {
     TaskRepresentationModel repModel = new TaskRepresentationModel();
     repModel.setTaskId(task.getId());
     repModel.setExternalId(task.getExternalId());