example-simple

Simple Camunda Spring Boot Application

This example only uses camunda-bpm-spring-boot-starter, so it does not start an embedded tomcat and provides no REST API. It demonstrates how Camunda can be used in combination with Spring Boot to spawn a node that:

• connects to a database (and sets it up if needed, in this case h2 in memory db)
• configures and starts a process engine
• deploys the 'sample.bpmn' process
• starts this process
• automatically executes the user task
• JobExecutor executes async service task
• once the process instance is ended, the spring boot application terminates

It also demonstrates the usage of application.yaml configuration file and contains a couple of integration tests, showing how this can be tested.

Prerequisites

• Java 17/21

How is it done

1. To embed Camunda Engine you must add the following dependency to your pom.xml:

...
<dependency>
 <groupId>org.camunda.bpm.springboot</groupId>
 <artifactId>camunda-bpm-spring-boot-starter</artifactId>
 <version>7.22.0</version>
</dependency>
...

2. With Spring Boot you usually create an "application" class annotated with @SpringBootApplication. In order to have a Camunda process application registered, you can simply add the annotation @EnableProcessApplication to the same class and also include the processes.xml file in your META-INF folder:

@SpringBootApplication
@EnableProcessApplication("mySimpleApplication")
public class SimpleApplication {

  public static void main(final String... args) throws Exception {
    SpringApplication.run(SimpleApplication.class, args);
  }

}

3. You can simply inject the engine services in your Spring beans using the @Autowired annotation.

4. You can also put BPMN, CMMN and DMN files in your classpath, they will be automatically deployed and registered within the process application.

5. When implementing the process application in standard manner, you can use method-level annotations @PostDeploy and @PreUndeploy to process corresponding events. In case of a Spring Boot process application you can handle this events by using Spring @EventListener annotation with following event classes: PostDeployEvent and PreUndeployEvent.

...
@EventListener
public void notify(PostDeployEvent event) {
...
}
...

Run the application and check the result

You can build the application with mvn clean install and then run it with the java -jar command.

Observe the log entries similar to these:

postDeploy: PostDeployEvent{processEngine=org.camunda.bpm.engine.impl.ProcessEngineImpl@6973b51b}
started instance: 0f1cd511-a1f0-11e7-8e5d-0a0027000006
completed task: Task[0f200964-a1f0-11e7-8e5d-0a0027000006]
executed sayHelloDelegate: ProcessInstance[380e1597-a206-11e7-8d39-0a0027000006]
processinstance ended!
preUndeploy: PreUndeployEvent{processEngine=org.camunda.bpm.engine.impl.ProcessEngineImpl@3be4ea5e}