Feature/27 execution listener

camunda-7-adapter/readme.md

@@ -78,13 +78,16 @@ expression, e.g.:
 </bpmn:serviceTask>
 ```
 
+If you are using an expression, you might want to write the result to a process variable. This can be achieved by setting an additional `resultVariable` header:
+
 ```xml
 
 <bpmn:serviceTask id="task3" name="Expression">
   <bpmn:extensionElements>
     <zeebe:taskDefinition type="camunda-7-adapter"/>
     <zeebe:taskHeaders>
       <zeebe:header key="expression" value="${someBean.awesomeMethod(execution, someVar)}"/>
+      <zeebe:header key="resultVariable" value="awesomeMethodResult"/>
     </zeebe:taskHeaders>
   </bpmn:extensionElements>
 </bpmn:serviceTask>
@@ -102,6 +105,22 @@ The external task workers can be mapped by using the `taskType` and insert the
 </bpmn:serviceTask>
 ```
 
+## Using Execution listener
+
+To use execution listeners, use the header `executionListener.start` or `executionListener.end`. The value should be of type `delegateExpression` which returns a bean of type `ExecutionListener`:
+
+```xml
+
+<bpmn:serviceTask id="task3" name="Expression">
+  <bpmn:extensionElements>
+    <zeebe:taskHeaders>
+      <zeebe:header key="executionListener.start" value="${startExecutionListenerBean}"/>
+      <zeebe:header key="executionListener.end" value="${endExecutionListenerBean}"/>
+    </zeebe:taskHeaders>
+  </bpmn:extensionElements>
+</bpmn:serviceTask>
+```
+
 ## Example
 
 Check out

camunda-7-adapter/src/main/java/org/camunda/community/migration/adapter/execution/SimpleVariableScope.java

@@ -16,9 +16,9 @@ public class SimpleVariableScope extends AbstractVariableScope {
 
   private static final long serialVersionUID = 1L;
 
-  protected VariableInstanceFactory<CoreVariableInstance> variableInstanceFactory = (name, value, isTransient) -> new SimpleVariableInstance(name, value);
-  protected VariableStore<SimpleVariableInstance> variableStore =
-      new VariableStore<SimpleVariableInstance>();
+  protected VariableInstanceFactory<CoreVariableInstance> variableInstanceFactory =
+      (name, value, isTransient) -> new SimpleVariableInstance(name, value);
+  protected VariableStore<CoreVariableInstance> variableStore = new VariableStore<>();
 
   public SimpleVariableScope() {
     this(Collections.emptyMap());
@@ -30,7 +30,7 @@ public SimpleVariableScope(Map<String, ?> variables) {
   }
 
   protected VariableStore<CoreVariableInstance> getVariableStore() {
-    return (VariableStore) variableStore;
+    return variableStore;
   }
 
   @Override

camunda-7-adapter/src/main/java/org/camunda/community/migration/adapter/worker/CamundaPlatform7DelegationWorker.java

@@ -42,13 +42,9 @@ public void delegateToCamundaPlatformCode(final JobClient client, final Activate
     final DelegateExecution execution = new ZeebeJobDelegateExecution(job);
 
     try {
-      if (startListener == null
-          && endListener == null
-          && delegateClass == null
-          && delegateExpression == null
-          && expression == null) {
+      if (delegateClass == null && delegateExpression == null && expression == null) {
         throw new RuntimeException(
-            "Either 'executionListener.start' or 'class' or 'delegateExpression' or 'expression' or executionListener.end must be specified in task headers for job :"
+            "Either 'class' or 'delegateExpression' or 'expression' must be specified in task headers for job :"
                 + job);
       }