This example demonstrates how to combine the REST API, Webapp and External Task Client Starters.
Beyond that, it demonstrates how to use the Spring Boot Starter to ...
- ... configure the External Task Client and topic subscriptions
- ... subscribe to topics so the client can fetch and lock for External Tasks
- ... execute custom business logic defined in a handler bean for each fetched External Task
- Java 17/21
This example shows how to configure and bootstrap an External Task Client using the application.yml file,
subscribe to topics to execute custom business logic using the @ExternalTaskSubscription
annotation, and configure these subscriptions using the application.yml file. Additionally, it shows
how to listen to the SubscriptionInitializedEvent, and open the subscription after the application
has been started.
Let's first add the dependencies to the project's pom.xml file:
<!--...-->
<dependency>
<groupId>org.camunda.bpm.springboot</groupId>
<artifactId>camunda-bpm-spring-boot-starter-external-task-client</artifactId>
<version>7.21.0</version>
</dependency>
<dependency>
<groupId>org.camunda.bpm.springboot</groupId>
<artifactId>camunda-bpm-spring-boot-starter-rest</artifactId>
<version>7.21.0</version>
</dependency>
<dependency>
<groupId>org.camunda.bpm.springboot</groupId>
<artifactId>camunda-bpm-spring-boot-starter-webapp</artifactId>
<version>7.21.0</version>
</dependency>
<!--...-->Second, we create an Application class and annotate it with @SpringBootApplication to enable the Starters:
@SpringBootApplication
public class Application {
public static void main(String... args) {
SpringApplication.run(Application.class, args);
}
}To configure the Runtime Platform admin user, the External Task Client, and the topic subscriptions,
we create an application.yml file:
camunda.bpm:
admin-user: # Configure the login credentials for the Runtime Platform admin user
id: demo # configure the username
password: demo # configure the password
client:
base-url: http://localhost:8080/engine-rest # The URL pointing to the Camunda Platform Runtime REST API
async-response-timeout: 1000 # Defines the maximum duration of the long-polling request
worker-id: spring-boot-client # Identifies the worker towards the Engine
# basic-auth: # Configure if REST API is secured with basic authentication
# username: demo
# password: demo
subscriptions:
creditScoreChecker: # This topic name must match the respective `@ExternalTaskSubscription`
process-definition-key: loan_process # Filters for External Tasks of this key
auto-open: false # Defines whether the subscription is opened automatically or not
loanGranter:
lock-duration: 10000 # Defines for how long the External Tasks are locked until they can be fetched againNext, we create a HandlerConfiguration class to subscribe to topics and add our custom
business logic by defining a bean with the return type ExternalTaskHandler and add the
@ExternalTaskSubscription annotation to the bean method. The lambda function's body contains
our custom business logic that is executed when an External Task is fetched. Additionally, we catch
the SubscriptionInitializedEvent to open a subscription after the application has ben started in case it is not opened already:
@Configuration
public class HandlerConfiguration {
protected static Logger LOG = LoggerFactory.getLogger(HandlerConfiguration.class);
protected String workerId;
public HandlerConfiguration(ClientProperties properties) {
workerId = properties.getWorkerId();
}
@ExternalTaskSubscription("creditScoreChecker")
@Bean
public ExternalTaskHandler creditScoreChecker() {
return (externalTask, externalTaskService) -> {
// retrieve a variable from the Process Engine
int defaultScore = externalTask.getVariable("defaultScore");
List<Integer> creditScores = new ArrayList<>(Arrays.asList(defaultScore, 9, 1, 4, 10));
// create an object typed variable
ObjectValue creditScoresObject = Variables.objectValue(creditScores).create();
// complete the external task
externalTaskService.complete(externalTask, Variables.putValueTyped("creditScores", creditScoresObject));
LOG.info("{}: The External Task {} has been checked!", workerId, externalTask.getId());
};
}
// ...
@EventListener(SubscriptionInitializedEvent.class)
public void catchSubscriptionInitEvent(SubscriptionInitializedEvent event) {
SpringTopicSubscription topicSubscription = event.getSource();
if (!topicSubscription.isAutoOpen()) {
// open topic in case it is not opened already
topicSubscription.open();
LOG.info("Subscription with topic name '{}' has been opened!",
topicSubscription.getTopicName());
}
}
}The BPMN model loan-granting.bpmn is automatically deployed
to the Process Engine since it is located under /src/main/resources/.
- Check out the project with Git
- Import the project into your IDE
- Start the main class in your IDE
- Watch out for the following log output:
____ _ ____ _ _ __
/ ___| __ _ _ __ ___ _ _ _ __ __| | __ _ | _ \ | | __ _ | |_ / _| ___ _ __ _ __ ___
| | / _` | | '_ ` _ \ | | | | | '_ \ / _` | / _` | | |_) | | | / _` | | __| | |_ / _ \ | '__| | '_ ` _ \
| |___ | (_| | | | | | | | | |_| | | | | | | (_| | | (_| | | __/ | | | (_| | | |_ | _| | (_) | | | | | | | | |
\____| \__,_| |_| |_| |_| \__,_| |_| |_| \__,_| \__,_| |_| |_| \__,_| \__| |_| \___/ |_| |_| |_| |_|
_____ _ _ _____ _ ____ _ _ _
| ____| __ __ | |_ ___ _ __ _ __ __ _ | | |_ _| __ _ ___ | | __ / ___| | | (_) ___ _ __ | |_
| _| \ \/ / | __| / _ \ | '__| | '_ \ / _` | | | | | / _` | / __| | |/ / | | | | | | / _ \ | '_ \ | __|
| |___ > < | |_ | __/ | | | | | | | (_| | | | | | | (_| | \__ \ | < | |___ | | | | | __/ | | | | | |_
|_____| /_/\_\ \__| \___| |_| |_| |_| \__,_| |_| |_| \__,_| |___/ |_|\_\ \____| |_| |_| \___| |_| |_| \__|
Spring-Boot: (v2.7.9)
Camunda Platform: (v7.21.0)
2021-03-19 10:57:54.493 INFO 23614 --- [ main] o.c.bpm.spring.boot.example.Application : Starting Application using Java 1.8.0_131 on localhost with PID 23614 (~//camunda-bpm-examples/spring-boot-starter/external-task-client/loan-granting-spring-boot-webapp/target/classes started by user in ~//camunda-bpm-examples/spring-boot-starter/external-task-client)
2021-03-19 10:57:54.495 INFO 23614 --- [ main] o.c.bpm.spring.boot.example.Application : No active profile set, falling back to default profiles: default
2021-03-19 10:57:55.766 INFO 23614 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
2021-03-19 10:57:55.784 INFO 23614 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2021-03-19 10:57:55.785 INFO 23614 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.41]
...
2021-03-19 10:58:02.537 INFO 23614 --- [ main] org.camunda.bpm.engine : ENGINE-00001 Process Engine default created.
2021-03-19 10:58:02.628 INFO 23614 --- [ main] org.camunda.bpm.spring.boot : STARTER-SB010 creating initial Admin User: AdminUserProperty[id=demo, firstName=Demo, lastName=Demo, email=demo@localhost, password=******]
...
2021-03-19 10:58:03.632 INFO 23614 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2021-03-19 10:58:03.659 INFO 23614 --- [ main] o.c.bpm.spring.boot.example.Application : Started Application in 9.51 seconds (JVM running for 10.128)
2021-03-19 10:58:03.674 INFO 23614 --- [ main] o.c.b.s.b.example.HandlerConfiguration : Subscription with topic name 'creditScoreChecker' has been opened!
2021-03-19 10:58:03.684 INFO 23614 --- [ main] org.camunda.bpm.engine.jobexecutor : ENGINE-14014 Starting up the JobExecutor[org.camunda.bpm.engine.spring.components.jobexecutor.SpringJobExecutor].
2021-03-19 10:58:03.690 INFO 23614 --- [ingJobExecutor]] org.camunda.bpm.engine.jobexecutor : ENGINE-14018 JobExecutor[org.camunda.bpm.engine.spring.components.jobexecutor.SpringJobExecutor] starting to acquire jobs
2021-03-19 10:58:12.363 INFO 23614 --- [criptionManager] o.c.b.s.b.example.HandlerConfiguration : spring-boot-client: The External Task 9bd0aca1-8899-11eb-85fb-8e4eb3fc8d8b has been checked!
2021-03-19 10:58:12.412 INFO 23614 --- [criptionManager] o.c.b.s.b.example.HandlerConfiguration : spring-boot-client: The External Task 9dc3a349-8899-11eb-85fb-8e4eb3fc8d8b has been rejected with score 4!
2021-03-19 10:58:12.425 INFO 23614 --- [criptionManager] o.c.b.s.b.example.HandlerConfiguration : spring-boot-client: The External Task 9dc3f171-8899-11eb-85fb-8e4eb3fc8d8b has been granted with score 10!
2021-03-19 10:58:12.439 INFO 23614 --- [criptionManager] o.c.b.s.b.example.HandlerConfiguration : spring-boot-client: The External Task 9dc37c31-8899-11eb-85fb-8e4eb3fc8d8b has been rejected with score 1!
2021-03-19 10:58:12.453 INFO 23614 --- [criptionManager] o.c.b.s.b.example.HandlerConfiguration : spring-boot-client: The External Task 9dc2b8d1-8899-11eb-85fb-8e4eb3fc8d8b has been rejected with score 5!
2021-03-19 10:58:12.471 INFO 23614 --- [criptionManager] o.c.b.s.b.example.HandlerConfiguration : spring-boot-client: The External Task 9dc306f9-8899-11eb-85fb-8e4eb3fc8d8b has been granted with score 9!