spring-servlet-pa-tomcat

Spring Servlet Process Application (using Tomcat 9)

This example demonstrates how to deploy a spring powered web application which

• Includes a @ProcessApplication class and some BPMN 2.0 processes
• Starts a Spring Web application context based on a shared, container managed process engine
• Uses Spring Beans and delegation code in expressions within processes

Why is this example interesting?

This example shows how to combine a @ProcessApplication class, a processes.xml and a spring applicationContext into a fully-fledged process application with all its advantages, including a shared, container managed process engine paired with the power of Spring Beans inside your processes.

Show me the important parts!

A process application class was created which extends the ServletProcessApplication class. The class was annotated with @ProcessApplication. This allows the Camunda Platform to pick it up and register the process application without any further action:

@ProcessApplication
public class SpringServletProcessApplication extends ServletProcessApplication {
  ...
}

Through the META-INF/processes.xml, we can define process archives and additional options, like creating new engines when deploying the process application:

<?xml version="1.0" encoding="UTF-8"?>
<process-application
  xmlns="http://www.camunda.org/schema/1.0/ProcessApplication"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.camunda.org/schema/1.0/ProcessApplication http://www.camunda.org/schema/1.0/ProcessApplication">

  <process-archive>
  <properties>
    <property name="isDeleteUponUndeploy">true</property>
  </properties>
  
  </process-archive>

</process-application>

Maven dependencies

The scope attributes of the camunda-engine dependency is set to provided since it is included in the shared classpath of the Camunda Tomcat distribution:

<dependency>
  <groupId>org.camunda.bpm</groupId>
  <artifactId>camunda-engine</artifactId>
  <version>${camunda.version}</version>
  <scope>provided</scope>
</dependency>

The scope of camunda-engine-spring, the module that integrates Camunda with Spring, must be set to compile so that it is included in the application.

<dependency>
  <groupId>org.camunda.bpm</groupId>
  <artifactId>camunda-engine</artifactId>
  <version>${camunda.version}</version>
</dependency>

For testing, the Maven Cargo plugin unpacks the Camunda Tomcat distribution to the target/tomcat directory of the application and runs it.

How to use it?

1. Build it with Maven.

mvn clean verify

This will start the embedded tomcat server.

2. Watch out for this console log:

[INFO] [talledLocalContainer] INFO: ENGINE-08046 Found Camunda Platform configuration in CATALINA_BASE/CATALINA_HOME conf directory [./target/cargo/configurations/tomcat9x/conf/bpm-platform.xml] at './target/cargo/configurations/tomcat9x/conf/bpm-platform.xml'
...
[INFO] [talledLocalContainer] INFO: ENGINE-07015 Detected @ProcessApplication class 'org.camunda.bpm.example.spring.servlet.pa.SpringServletProcessApplication'
[INFO] [talledLocalContainer] Sep 23, 2021 9:35:01 AM org.apache.catalina.core.ApplicationContext log
[INFO] [talledLocalContainer] INFO: Initializing Spring root WebApplicationContext
...
[INFO] [talledLocalContainer] INFO: Invoking @PostDeploy annotation in org.camunda.bpm.example.spring.servlet.pa.SpringServletProcessApplication
[INFO] [talledLocalContainer] Starting testResolveBean processdefinition
[INFO] [talledLocalContainer] Sep 23, 2021 9:35:01 AM org.camunda.bpm.example.spring.servlet.pa.ExampleBean invoke
[INFO] [talledLocalContainer] INFO: org.camunda.bpm.example.spring.servlet.pa.ExampleBean is currently invoked.
[INFO] [talledLocalContainer] Sep 23, 2021 9:35:01 AM org.camunda.bpm.example.spring.servlet.pa.SpringServletProcessApplication startProcess
[INFO] [talledLocalContainer] INFO: Starting testResolveBeanFromJobExecutor processdefinition
[INFO] [talledLocalContainer] Sep 23, 2021 9:35:01 AM org.camunda.bpm.example.spring.servlet.pa.ExampleDelegateBean execute
[INFO] [talledLocalContainer] INFO: org.camunda.bpm.example.spring.servlet.pa.ExampleDelegateBean is currently invoked.
[INFO] [talledLocalContainer] Sep 23, 2021 9:35:01 AM org.camunda.commons.logging.BaseLogger logInfo
[INFO] [talledLocalContainer] INFO: ENGINE-08050 Process application camunda-quickstart-spring-servlet-pa-tomcat successfully deployed