camunda-7-adapter

Spring Boot Adapter to re-use Java Delegates, Delegate Expressions, Expressions or External Tasks from Camunda Platform 7 in Camunda Platform 8

This library allows to reuse Java delegates, Delegate Expressions, Expressions or External Tasks from process solutions developed for Camunda Platform 7 (with Spring/Spring Boot) within Camunda Platform 8.

The adapter requires to use Spring Boot.

Details on how service tasks are adapted are described in this migration guide.

Important note:* This adapter does not aim to cover every possible situation, but it might work out-of-the-box for some cases or give you jump-start to extend it to suite your needs.

How to use

Add dependency

Add the dependency to the adapter library (double-check for the latest version):

<dependency>
  <groupId>org.camunda.community.migration</groupId>
  <artifactId>camunda-7-adapter</artifactId>
  <version>0.6.2</version>
</dependency>

Import adapter

Import the adapter into your Spring Boot application as shown in the example application:

@SpringBootApplication
@EnableCamunda7Adapter
@Deployment(resources = "classpath:*.bpmn")
public class Application {
  // start off here
}

This will start a job worker that subscribes to camunda-7-adapter as well as workers for each @ExternalTaskSubscription with Zeebe Task Type equal to External Task Topic Name.

Using migration worker

To use that worker, add the taskType="camunda-7-adapter" to your service task and add task headers for a java delegate class, delegate expression or expression, e.g.:

<bpmn:serviceTask id="task1" name="Java Delegate">
  <bpmn:extensionElements>
    <zeebe:taskDefinition type="camunda-7-adapter"/>
    <zeebe:taskHeaders>
      <zeebe:header key="class" value="org.camunda.community.migration.example.SampleJavaDelegate"/>
    </zeebe:taskHeaders>
  </bpmn:extensionElements>
</bpmn:serviceTask>

<bpmn:serviceTask id="task2" name="Delegate Expression">
  <bpmn:extensionElements>
    <zeebe:taskDefinition type="camunda-7-adapter"/>
    <zeebe:taskHeaders>
      <zeebe:header key="delegateExpression" value="${myAwesomeJavaDelegateBean}"/>
    </zeebe:taskHeaders>
  </bpmn:extensionElements>
</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:

<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>

The external task workers can be mapped by using the taskType and insert the topicName there.

<bpmn:serviceTask id="task4" name="External Task Worker">
  <bpmn:extensionElements>
    <zeebe:taskDefinition type="my-awesome-topic"/>
  </bpmn:extensionElements>
</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:

<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>

Handling Object Variables

As Zeebe does not support explicit typing anymore (everything is JSON), it is not possible to retrieve typed variables from the process instance directly.

To overcome this, the adapter can be enriched with Variable Typing Rules.

They are using the bpmnProcessId and the variableName to determine how a variable value needs to be typed.

There is a default implementation in place that uses an object mapper for generic mapping.

All rules can be registered as @Components and will be picked up and applied automatically.

Example

Check out the full example for more details.