How can I get the process with SpingBoot 2.7.3 and Flowable 6.7.2?

Question

I have a Controller:

@RestController
@RequestMapping("processes")
public class ProcessController {
    @Autowired
    private ProcessEngine processEngine;

    @Autowired
    private RepositoryService repositoryService;

    @GetMapping
    public List<ProcessDefinition> listProcess() {
        return processEngine.getRepositoryService().createProcessDefinitionQuery().list();
    }

    @PostMapping(consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    public Deployment addProcess(@RequestPart MultipartFile file) throws IOException {
        return repositoryService.createDeployment().addInputStream(file.getOriginalFilename(), file.getInputStream()).deploy();
    }
}

And I have already upload the test.bpmn20.xml with the addProcess() method, but when I want to get ProcessDefinition list with the listProcess method, the console warning:

Resolved [org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: Cannot invoke "org.flowable.engine.impl.cfg.ProcessEngineConfigurationImpl.getIdentityLinkServiceConfiguration()" because "processEngineConfiguration" is null; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Cannot invoke "org.flowable.engine.impl.cfg.ProcessEngineConfigurationImpl.getIdentityLinkServiceConfiguration()" because "processEngineConfiguration" is null (through reference chain: java.util.ArrayList[0]->org.flowable.engine.impl.persistence.entity.ProcessDefinitionEntityImpl["identityLinks"])]

My POM.xml:

    <dependency>
      <groupId>org.flowable</groupId>
      <artifactId>flowable-spring-boot-starter</artifactId>
      <version>6.7.2</version>
    </dependency>

Why console warning this? What can I do?

Pls help me, thx!

score 2 · Accepted Answer · answered Sep 05 '22 at 08:52

To return a variable from a REST endpoint in Spring it needs to convert the variable to a JSON. However, Flowable API responses are not optimized to be converted to DTOs. That is why you may not be able to return them directly as a response variable.

For example:

@RestController
@RequestMapping("processes")
public class ProcessController {
    @Autowired
    private ProcessEngine processEngine;

    @Autowired
    private RepositoryService repositoryService;

    // ...

    @PostMapping(consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    public DeploymentDto addProcess(@RequestPart MultipartFile file) throws IOException {
        Deployment deployment = repositoryService.createDeployment()
                .addInputStream(file.getOriginalFilename(), file.getInputStream())
                .deploy();
        return new DeploymentDto(deployment);
    }

    private static class DeploymentDto {
        private final String id;
        private final String name;

        public DeploymentDto(Deployment deployment) {
            this.id = deployment.getId();
            this.name = deployment.getName();
        }

        public String getId() {
            return id;
        }

        public String getName() {
            return name;
        }
    }
}

You can create your own DTO objects and map the result from the Flowable API to your DTO. Alternatively, you could use the flowable-spring-boot-starter-rest dependency which gives you out-of-the-box REST endpoints. The mapping there is automatically handled for you. (See the getting started guide for more information https://www.flowable.com/open-source/docs/bpmn/ch05a-Spring-Boot/#getting-started)

But when I add this to the main() method: ```java @Bean public CommandLineRunner init(final RepositoryService repositoryService) { return strings -> { System.out.println(repositoryService.createDeploymentQuery().list()); }; } ``` The console print `[DeploymentEntity[id=19b43ccf-2cf7-11ed-9097-00ff3a86941e, name=test.bpmn20.xml]]`, this is the result I want. Why? And how to use it in my Controller? — Dexuan yang, Sep 05 '22 at 09:13
In this case the `.toString()` method is executed rather than a JSON serialization. You can get this with the following getter method: `@GetMapping public String listProcess() { return repositoryService.createProcessDefinitionQuery().list().toString(); }` Typically however, you would rather like to have a JSON response as described above. — Valentin Zickner, Sep 06 '22 at 04:22

How can I get the process with SpingBoot 2.7.3 and Flowable 6.7.2?

1 Answers1