Java World Knowledge Sharing Portal: Passing data from External service task to Delegate Service task Camunda

In this we will try to do following things

1- we will create a sevice task (external) that will send data to another service task (delegate) and we will check if the data is send properly or not using embedded camunda.

In past example https://shdhumale.wordpress.com/2023/04/24/calling-java-class-from-camunda-task-process/
we had tried to create bpmn file that will ask for user inpur when uploaded on the camunda server and when we start our springboot application it will contant this service task in bmnp file and fetch the value that is entered by the user using ExternalTaskHandler.
Now lets talk about the second concept we had talk above i.e. using Delegate in sprigboot.

In this exercise we wil get the input from bpmn files and then modify it in our java class and then we are transeferring the two values from spring boot class to another Service task in bpmn file service task that will send that values to our other java class using delegate.

Please flow below step religiously

1- Create a bpmn file
2- upload that file on local standalone camunda server.
3- Write java class with ExternalTaskHandler that will take input parameter from bpmn files.
4- finally we will modify this input paramter and send it back to another bpmn service which send the data to java class using delegate and will dispaly the modified values.

lets start

1- Create a bpmn file:-

Please follow below steps.

2- upload that file on local standalone camunda server.

Start you standalone camunda server and login to the tasklist using demo/demo.

follow below steps to upload bpmn files.

Go to below url and start the process.

check the process is imported properly using belwo url

http://localhost:8080/camunda/app/cockpit/default/#/processes

now lets start the process using belwo url

http://localhost:8080/camunda/app/tasklist/default/#/?searchQuery=%5B%5D&filter=7ecb3220-d2db-11ed-86b7-7e7a91225434&sorting=%5B%7B%22sortBy%22:%22created%22,%22sortOrder%22:%22desc%22%7D%5D

3- Write java class with ExternalTaskHandler that will take input parameter from bpmn files.

follow below steps for the same.

https://start.spring.io/starter.zip?name=siddhu-external-delegate&groupId=com.siddhu&artifactId=siddhu-external-delegate&version=0.0.1-SNAPSHOT&description=This+example+shows+calling+Java+class+from+Camunda+Process+using+handler+and+then+sending+value+back+to+another+java+class+using+delegate+via++Service+task+&packageName=com.siddhu.camunda&type=maven-project&packaging=jar&javaVersion=1.8&language=java&bootVersion=3.0.6

Now update the pom.xml as

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.7.3</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.siddhu</groupId>
    <artifactId>siddhu-external-delegate</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>siddhu-external-delegate</name>
    <description>This example shows calling Java class from Camunda Process using handler and then sending value back to another java class using delegate via  Service task </description>
    <properties>
        <java.version>1.8</java.version>
        <camunda.platform.runtime.version>7.18.0</camunda.platform.runtime.version>
        <spring.boot.version>2.7.3</spring.boot.version>
        <maven.compiler.plugin.version>3.8.1</maven.compiler.plugin.version>
    </properties>
    <dependencies>
 
        <dependency>
            <groupId>org.camunda.bpm.springboot</groupId>
            <artifactId>camunda-bpm-spring-boot-starter-external-task-client</artifactId>
            <version>${camunda.platform.runtime.version}</version>
        </dependency>
 
        <dependency>
            <groupId>com.sun.xml.bind</groupId>
            <artifactId>jaxb-impl</artifactId>
            <version>2.3.5</version>
        </dependency>
 
    </dependencies>
 
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>${spring.boot.version}</version>
                <executions>
                    <execution>
                        <id>repackage</id>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
 
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>${maven.compiler.plugin.version}</version>
                <configuration>
                    <source>8</source>
                    <target>8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
 
</project>

Check project is compiling and building properly using belwo screen after modification in pom.xml

But first change the application.yaml files.

camunda.bpm.client:
  base-url: http://localhost:8080/engine-rest # the URL pointing to the Camunda Platform Runtime REST API
  lock-duration: 10000 # defines how many milliseconds the External Tasks are locked until they can be fetched again
  subscriptions:  
    changevalue: # This is topic name
      variable-names: name,age # only fetch these variables
      process-definition-key: siddhuexternaldelegate #this is the id that we give for process ID
camunda.bpm:
  admin-user:
    id: demo
    password: demo
    firstName: Demo
  filter:
    create: All tasks 

Now lets create our java class that will be called from our camunda process

1

Now lets run the application and check we are able to get the name and age that we set in start of bpmn files

Now lets change this value in our class and send it to our another service task.

Please follow below process religiously

https://start.spring.io/starter.zip?name=siddhu-delegate-task&groupId=com.siddhu&artifactId=siddhu-delegate-task&version=0.0.1-SNAPSHOT&description=This+example+take+value+send+from+java+ExternalTaskHandler+from+one+of+the+service+task+to+respective+this+task&packageName=com.siddhu.camunda&type=maven-project&packaging=jar&javaVersion=1.8&language=java&bootVersion=3.0.6&dependencies=h2&dependencies=web

Now lets modify our pom.xml as given below to inject dependencies

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.1</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.siddhu</groupId>
    <artifactId>siddhu-delegate-task</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>siddhu-delegate-task</name>
    <description>This example take value send from java ExternalTaskHandler from one of the service task to respective this task</description>
    <properties>
        <java.version>8</java.version>
        <camunda.spring-boot.version>7.16.0</camunda.spring-boot.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
 
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
 
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.camunda.bpm.springboot</groupId>
            <artifactId>camunda-bpm-spring-boot-starter-webapp</artifactId>
            <version>${camunda.spring-boot.version}</version>
        </dependency>
        <dependency>
            <groupId>org.camunda.bpm.springboot</groupId>
            <artifactId>camunda-bpm-spring-boot-starter-rest</artifactId>
            <version>${camunda.spring-boot.version}</version>
        </dependency>
 
        <dependency>
            <groupId>com.sun.xml.bind</groupId>
            <artifactId>jaxb-impl</artifactId>
            <version>2.3.5</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context-support</artifactId>
            <version>5.2.8.RELEASE</version>
        </dependency>
 
    </dependencies>
 
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
 
</project>

Now make following files

1- SiddhuDelegateTaskApplication
 
package com.siddhu.camunda;
 
import org.camunda.bpm.spring.boot.starter.annotation.EnableProcessApplication;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
 
@SpringBootApplication
@EnableProcessApplication
public class SiddhuDelegateTaskApplication {
 
    public static void main(String[] args) {
        SpringApplication.run(SiddhuDelegateTaskApplication.class, args);
    }
 
}
 
 
2-ServletInitializer
 
package com.siddhu.camunda;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
 
public class ServletInitializer extends SpringBootServletInitializer {
 
    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(SiddhuDelegateTaskApplication.class);
    }
 
}
 
3- DelegateTask
 
package com.siddhu.camunda;
import javax.inject.Named;
 
import org.camunda.bpm.engine.delegate.DelegateExecution;
import org.camunda.bpm.engine.delegate.JavaDelegate;
@Named
public class DelegateTask implements JavaDelegate{
 
    @Override
    public void execute(DelegateExecution execution) throws Exception {
        // TODO Auto-generated method stub
 
        String name=(String) execution.getVariable("name");
        String status=(String) execution.getVariable("status");
         
        System.out.println("name"+name);
        System.out.println("status"+status);
                 
    }
     
}
 
4- application.yaml
 
camunda.bpm:
  admin-user:
    id: demo
    password: demo
    firstName: Demo
  filter:
    create: All tasks

Now first stop the standalone server and Now lets start our this application and check if we are getting this modified value inside our java class from next service task

now start our siddhu-external-delegate project

Now lets upload our bpnm file using moduler

Now lets start our deployed process

Check the values in our java programe

now you might be thinking was is difference between ExternalTaskHandler and delegate
let me try to expalin the same as we have use these both concept here.