Return Java Object from Process Engine

Camunda 7 Topics Discussion & Questions
1

Hello everyone (I’m new in this forum so please don’t judge me :pray:),
To my question: Is it possible to return Java Objects (or at least Json) from the Process Engine?

I’m doing some testing on processes with Spring Boot Camunda. I need to start a process with a process variable which I set as Java Object. I want to modify this object within a Java Delegate and test afterwards that the changes were done right. I have tried it with HistoricVariableInstance but i just get the name of process variables. I don’t know how to modify this object via DelegateExecution, but HistoricVariableInstance still returns empty values. Can someone help?

@SpringBootTest(classes = ProcessApplication.class)
@TestPropertySource(locations = { "classpath:test.properties" })
public class TestJsonThroughProcessTestNG extends AbstractTestNGSpringContextTests {
    @Autowired
    RuntimeService runtimeService;
    @Autowired
    ProcessEngine processEngine;
    private Record cr;
    @BeforeMethod
    public void setUp() {
        this.mapper = new ObjectMapper();
        cr = new Record();
        cr.setId(Integer.valueOf(1234));
        cr.setFirstName("Max");
        cr.setLastName("Mustermann");
        cr.setComplaintDate(Instant.now());
        cr.setListOfThings(new ArrayList<String>(Arrays.asList("here", "there", "everywhere")));
    }
    @Test
    public void testGetObject() {
        ProcessInstance pi = this.runtimeService.startProcessInstanceByKey("sendResponseTest",
                Variables.createVariables().putValue("Record", cr));
        List<HistoricVariableInstance> variables = this.processEngine.getHistoryService()
                .createHistoricVariableInstanceQuery().processInstanceId(pi.getId()).list();
}

Greetings
Alex

2

Hi @Haagy,

See https://docs.camunda.org/manual/7.9/user-guide/process-engine/variables/#java-object-api for how to set and access object variables from within a JavaDelegate. In addition, you can access the historic variable value via HistoricVariableInstance#getValue.

Cheers,
Thorben

3

Good morning @thorben,

I guess it would work, but I’m getting some deserialize errors.

org.camunda.bpm.engine.ProcessEngineException: Cannot deserialize object in variable 'Record': SPIN/JACKSON-JSON-01006 Cannot deserialize '{"id":1234...' to java type '[simple type, class com.example.camunda.pojo.Record]'

Caused by: org.camunda.spin.json.SpinJsonException: SPIN/JACKSON-JSON-01006 Cannot deserialize '{"id":1234...' to java type '[simple type, class com.example.camunda.pojo.Record]'

Caused by: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `java.time.Instant` (no Creators, like default construct, exist): cannot deserialize from Object value (no delegate- or property-based Creator)
 at [Source: UNKNOWN; line: -1, column: -1] (through reference chain: com.example.camunda.pojo.Record["ComplaintDate"])

Is that because I’m using Instant as datatype for date and the Process Engine can’t parse it?

Greetings,
Alex

4

I’ve tested it and Instant is the problem. Any suggestions how to do this properly?

5