Camunda Team Blog

Camunda External Task Client (Java) 0.1.0-alpha2 Released

Written by Tassilo Weidner on , under Execution category.

Recently we released the first alpha version of the Camunda External Task Client (Java). Today we are happy to announce the second alpha release.

The External Task concept helps to decouple your services from the Workflow Engine.

The highlights of this release are:

  • Set variables to the local scope of External Tasks
  • Specify a response timeout to fetch and lock External Tasks (long polling)
  • More serialization formats to exchange object variables (XML and JAVA)

You can find the complete release notes here.

Handling Orders Example

This example showcases some of the new features. Let’s consider the following workflow:

A Workflow for Handling Orders

A Workflow for Handling Orders

Make sure that you have an up and running Camunda Workflow Engine and deploy this workflow to it.

Next, create a Maven project and adjust the pom.xml by adding the following Maven coordinates:

<dependency>
  <groupId>org.camunda.bpm</groupId>
  <artifactId>camunda-external-task-client</artifactId>
  <version>0.1.0-alpha2</version>
</dependency>

Create a simple invoice class:

public class Invoice {
  public String id;

  public Invoice(String id) {
    this.id = id;
  }
}

Create a main class and add the following lines to it:

// bootstrap the client
ExternalTaskClient client = ExternalTaskClient.create()
  .baseUrl("http://localhost:8080/engine-rest")
  .asyncResponseTimeout(1000)
  .build();

// subscribe to the topic
client.subscribe("invoiceCreator")
  .handler((externalTask, externalTaskService) -> {

    // instantiate an invoice object
    Invoice invoice = new Invoice("A123");

    // create an object typed variable with the serialization format XML
    ObjectValue invoiceValue = Variables
      .objectValue(invoice)
      .serializationDataFormat("application/xml")
      .create();

    // add the invoice object and its id to a map
    Map<String, Object> variables = new HashMap<>();
    variables.put("invoiceId", invoice.id);
    variables.put("invoice", invoiceValue);

    // select the scope of the variables
    boolean isRandomSample = Math.random() <= 0.5;
    if (isRandomSample) {
      externalTaskService.complete(externalTask, variables);
    } else {
      externalTaskService.complete(externalTask, null, variables);
    }

    System.out.println("The External Task " + externalTask.getId() +
      " has been completed!");

  }).open();

Thread.sleep(1000 * 60 * 5);

Finally, run the application. You should see the following output:

The External Task 1d375217-2cfe-11e8-96c2-769e8e30ca9b has been completed!
The External Task 0857150d-2cfe-11e8-96c2-769e8e30ca9b has been completed!
...

The project sources of this example can be found here. Please also see the documentation of the External Task Client.

What do you think about this release? Share your ideas and suggestions with us in the forum.