chore(engine): allow setting custom AcquireJobsCommandFactory before …

…starting JobExecutor

Related to CAM-13163

engine/src/main/java/org/camunda/bpm/engine/impl/jobexecutor/JobExecutor.java

@@ -96,7 +96,9 @@ public synchronized void shutdown() {
   }
 
   protected void ensureInitialization() {
-    acquireJobsCmdFactory = new DefaultAcquireJobsCommandFactory(this);
+  if (acquireJobsCmdFactory == null) {
+    acquireJobsCmdFactory =  new DefaultAcquireJobsCommandFactory(this);
+  }
     acquireJobsRunnable = new SequentialJobAcquisitionRunnable(this);
   }
 

engine/src/test/java/org/camunda/bpm/engine/test/jobexecutor/JobExecutorStartTest.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright Camunda Services GmbH and/or licensed to Camunda Services GmbH
+ * under one or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership. Camunda licenses this file to you under the Apache License,
+ * Version 2.0; you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.camunda.bpm.engine.test.jobexecutor;
+
+import org.camunda.bpm.engine.impl.interceptor.Command;
+import org.camunda.bpm.engine.impl.jobexecutor.AcquireJobsCommandFactory;
+import org.camunda.bpm.engine.impl.jobexecutor.AcquiredJobs;
+import org.camunda.bpm.engine.impl.jobexecutor.DefaultAcquireJobsCommandFactory;
+import org.camunda.bpm.engine.impl.jobexecutor.DefaultJobExecutor;
+import org.camunda.bpm.engine.impl.jobexecutor.JobExecutor;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class JobExecutorStartTest {
+
+  private JobExecutor jobExecutor;
+
+  @Before
+  public void setUp() throws Exception {
+    jobExecutor = new DefaultJobExecutor();
+  }
+
+  @After
+  public void tearDown() throws Exception {
+    jobExecutor.shutdown();
+  }
+
+  @Test
+  public void shouldUseDefaultInitialization() {
+    //when
+    jobExecutor.start();
+
+    //then
+    assertThat(jobExecutor.getAcquireJobsCmdFactory()).isNotNull();
+    assertThat(jobExecutor.getAcquireJobsRunnable()).isNotNull();
+    assertThat(jobExecutor.getAcquireJobsCmdFactory()).isInstanceOf(DefaultAcquireJobsCommandFactory.class);
+    assertThat(jobExecutor.isActive()).isTrue();
+  }
+
+  @Test
+  public void shouldUseCustomJobsCmdFactoryAfterInitialization() {
+
+    // given
+    MyAcquireJobsCmdFactory myFactory = new MyAcquireJobsCmdFactory();
+    jobExecutor.setAcquireJobsCmdFactory(myFactory);
+
+    // when
+    jobExecutor.start();
+
+    // then
+    assertThat(jobExecutor.getAcquireJobsCmdFactory()).isSameAs(myFactory);
+    assertThat(jobExecutor.isActive()).isTrue();
+  }
+
+  public static class MyAcquireJobsCmdFactory implements AcquireJobsCommandFactory {
+    @Override
+    public Command<AcquiredJobs> getCommand(int numJobsToAcquire) {
+      return null;
+    }
+  }
+}