Error: One of the attributes 'class', 'delegateExpression', 'type', or 'expression' is mandatory on serviceTask

Camunda 7 Topics Discussion & Questions
1

Created a process below. Objective of the process is to call a REST URL through Service task after every certain timecycle(for testing I am doing every 2 minutes)

After this while trying to execute the spring code, getting the error as - *** One of the attributes ‘class’, ‘delegateExpression’, ‘type’, or ‘expression’ is mandatory on serviceTask…**

pom.xml (2.4 KB) process.bpmn (3.0 KB)

2

Which version of Camunda and which version of the modeler are you using?

3

Hi Niall,
Using modeler version of 4.8.1 and camunda version in pom.xml as 7.15.0.
It got fixed. juts added the below entry in POM.XML

 <dependency>
        <groupId>org.camunda.bpm</groupId>
        <artifactId>camunda-engine-plugin-connect</artifactId>
    </dependency>
    <dependency>
        <groupId>org.camunda.connect</groupId>
        <artifactId>camunda-connect-http-client</artifactId>
    </dependency>
1 Like
4

Glad to hear you’ve got it working :slight_smile:

5

@Niall , Thank you for the guidance and support. I have a requirement as below:
Outside of Camunda have to perform the below -

  1. Pull a json object from kafka cluster using kafkaListener.

  2. Once the JSON object is consumed in that kafkaconsumer class( service class in a spring boot as below ), that class should call/start a camunda process to validate the class. any idea how to call a process from service class
    ====================================
    @Service
    public class EventsstreamKafkaConsumer {

    private final Logger logger = LoggerFactory.getLogger(EventsstreamKafkaConsumer.class);
    @KafkaListener(topics = “test_topic” , groupId = “eventstreamgroup”)
    public void consumefromTopic (Event event)
    {
    logger.info(String.format(“Event is listened from Kafka Cluster through consumer api-> %s”, event));

    }

}

6

It depends,
If you’re using spring boot and KafkaConsumer is in the same application, you can just inject the RuntimeService as a bean and then start a process via the JavaAPI.

7

@Niall -Thank You. and is there any way I can pass my class object to a process while starting a process via Java API?

8 
@Autowired
private RuntimeService runtimeService;

//implementation code goes here
Map<String, Object> processVariablesMap;

runtimeService.startProcessInstanceByKey(processDefinitionKey, businessKey,
						processVariablesMap)
1 Like
10

Thank You Sir for your help. Now, I am able to initiate the workflow from Springboot and able to pass the object. I created one User Task to validate the object value and I can see the desiralized content contains the object value. Would be great if you can guide on the required properties need to get configured so that I can pass this Object from one service task to another service task.

code is as below for ref:

  1. Code that initiate the workflow in Camunda and send the object

import java.util.HashMap;
import java.util.Map;
import org.camunda.bpm.engine.RuntimeService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class EventWorkflowInitiator {

@Autowired
private RuntimeService runtimeService;

public void initiateworkflow(Event event)

{
	Map<String, Object> processVariablesMap = new HashMap<String, Object>();
	processVariablesMap.put("Event", event);

	runtimeService.startProcessInstanceByKey("EventStreamProcessId", processVariablesMap);
	
}

}

Code for next service task where I will be needed the Object to invoke that has been passed to CamundaEvent_1.bpmn (3.8 KB) .
@Component
public class EventParser implements JavaDelegate{

public void execute(DelegateExecution execution) throws Exception {
	System.out.println("within parser");
	
}