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Install the Activiti Eclipse Designer plugin. For instructions on installation, see the Activiti user guide.
Open Eclipse and go to File>New>Other and search for the Activiti project wizard to create a new Activiti project.
Go to File>New>Other and search for the Activiti Diagram wizard to create a new Activiti diagram.
Select the <Activiti_Project>/src/main/resources/diagrams directory as the parent folder.
Add a Start event, Service Task and End Event as seen below to create a basic process. Link each activity by hovering over the element, selecting the arrow sign and dragging it to the connecting element.
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Note
You can use a BPMN REST task to invoke a REST endpoint within your BPMN process. For more information on how to do this, see Invoking a BPMN REST Endpoint.
Create a Java project for HelloWorld Service Task by navigating to File>New>Other and searching for the Java Project Wizard.
Right-click on the project "HelloWorldServiceTask" and go to Build Path>Configure Build Path.
Click on Add External JARs under the Libraries tab and add the activiti-all_5.19.0.wso2v2.jar file ( or later version ) found in the <BPS_Home>/repository/components/plugins directory.
Go to File>New>Other and search for the Package wizard to create a Java package and name it "org.wso2.bpmn.helloworld.v1".
Go to File>New>Class to create a Java Class for HelloWorld Service task implementation.
Add org.activiti.engine.delegate.JavaDelegate interface to your class.

Implement the HelloWorld Service Task following the business logic in the HelloWorldServiceTaskV1.java file as seen below.

Code Block

language	java

package org.wso2.bpmn.helloworld.v1;

import org.activiti.engine.delegate.DelegateExecution;
import org.activiti.engine.delegate.JavaDelegate;
/**
 *	Hello World Service Task- V1. 
 */
public class HelloWorldServiceTaskV1 implements JavaDelegate {

	@Override
	public void execute(DelegateExecution arg0) throws Exception {
		System.out.println("Hello World ...!!!");

	}

}

Configure the HelloWorld Service Task Class name in the properties panel.

Panel

title	Best Practices

Note

title	Versioning

When you create a Java Service Task, version your java package or classes by adding version number into Java Package path or Class name. This is useful when you have multiple versions of the same workflow and you are changing Service task business logic in each process version. Having versions will avoid business logic changes in service tasks from affecting new or running process instances which are created from the old process version. An example of this can be seen below.

Code Block

language	java
title	Version 1

package org.wso2.bpmn.helloworld.v1;

import org.activiti.engine.delegate.DelegateExecution;
import org.activiti.engine.delegate.JavaDelegate;
/**
 *	Hello World Service Task- V1. 
 */
public class HelloWorldServiceTaskV1 implements JavaDelegate {

	@Override
	public void execute(DelegateExecution arg0) throws Exception {
		System.out.println("Hello World ...!!!");

	}

}

Code Block

language	java
title	Version 2

package org.wso2.bpmn.helloworld.v2;

import org.activiti.engine.delegate.DelegateExecution;
import org.activiti.engine.delegate.JavaDelegate;

/**
* Hello World Service Task - Version 2.
*/

public class HelloWorldServiceTaskV2 implements JavaDelegate {

@Override
  public void execute(DelegateExecution arg0) throws Exception {
  // In version 2, Hello World string is improved.
  System.out.println("Hello World ...!!! This is Second version of HelloWorld BPMN process.");
  }

}

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Versions Compared

Old Version 4

New Version 5

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