Zeebe EJB Client

Overview

Zeebe EJB Client Library

This repository contains a library that enables your JavaEE application as a Client for the Camunda-Platform-8 process engine.

You can reuse your existing JavaEE code and use @ApplicationScoped beans in a job handler as the implementation for BPMN Service tasks and other elements.

The library contains a single startup bean to activate the workers. (ZeebeEjbProcessApplication)

All application scoped beans that are annotated with @JobWorker(type = "mytype") are registered as workers on the Zeebe process engine.

Configuration

The Library uses the Zeebe java client configuration properties.

It reads a file named zeebeClient.properties from the class-path.

Connection properties for Camunda 8 SaaS Cloud cluster:

zeebe.client.cloud.clusterId=xxx
zeebe.client.cloud.clientId=xxx
zeebe.client.cloud.secret=xxx
zeebe.client.cloud.region=bru-2

Connection properties for a local installation with Docker compose:

zeebe.client.gateway.address=localhost:26500
zeebe.client.security.plaintext=true

Other client connection properties are mentioned in this class: io.camunda.zeebe.client.ClientProperties

Camunda 7 CDI Adapter

To reuse existing CDI DelegateExpressions in Camunda 8, you can add this library to your project:

	<dependency>
	  <groupId>org.camunda.community.client</groupId>
	  <artifactId>camunda-7-cdi-adapter</artifactId>
	  <version>0.0.2</version>
	</dependency>

It will use a task type camunda-7-adapter and look for configurations like <zeebe:header key="delegateExpression" value="${customerCreditDelegate}" />. These elements are created during the migration of the BPMN Diagram from Camunda 7 to Camunda 8 with the Diagram Converter.

The full XML element of a service task using the Camunda 7 CDI adapter:

    <bpmn:serviceTask id="Activity_1vwtc60" name="Deduct customer credit">
      <bpmn:extensionElements>
        <zeebe:taskDefinition type="camunda-7-adapter" />
        <zeebe:taskHeaders>
          <zeebe:header key="delegateExpression" value="${customerCreditDelegate}" />
        </zeebe:taskHeaders>
      </bpmn:extensionElements>
      <bpmn:incoming>Flow_04h7vab</bpmn:incoming>
      <bpmn:outgoing>Flow_0tr3idd</bpmn:outgoing>
    </bpmn:serviceTask>

Examples

Reuse existing Java EE Beans in your new Worker

This repository also contains an example that shows how to reuse existing EJBs in your Zeebe client on a Java-EE Server.

The Zeebe EJB client library registers all methods and classes that are annotated with @JobWorker(taskType="myType").

The Job workers require an @ApplicationScoped annotation for this. See CustomerCreditWorker.java.

The Service implementation itself gets injected to the worker. They are annotated with @Stateless. See CustomerService.java

To run the examples, you can deploy it to a running Wildfly server with mvn clean wildfly:deploy. During deployment all workers are registered in the Zeebe process engine and get activated.

You can find the full example here.

Start process instances

The example contains a REST Api to start process instances. Check the content of the package com.camunda.consulting.zeebe_ejb.rest.

To start process instances, use a REST client like curl:

curl for cmd.exe

curl --location --request POST "http://localhost:8080/zeebe-ejb-example-worker-interface/payment/command/start/" ^
--header "Content-Type: application/json" ^
--data-raw "{\"customerId\": \"12\", \"orderTotal\": 39.99, \"creditCardNumber\": \"1234123412341234\", \"cvc\": \"789\", \"expiryDate\": \"07/24\"}"

Reuse the DelegateExpression implementation

Just replace the Camunda 7 engine dependency with the camunda-7-cdi-adapter dependency in the pom.xml.

And add the connection properties pointing to the Zeebe cluster to your project.

You can find the complete example here.