Introduction to bpmn-js

bpmn-js is a powerful library for creating and managing BPMN 2.0 diagrams in the browser. It is a complete toolkit that allows developers to implement complex workflow and process automation systems with ease. In this tutorial, we will explore various APIs provided by bpmn-js to help you understand how to use this library effectively. We will start with basic operations and gradually move to more advanced features, including a comprehensive app example integrating multiple APIs.

Getting Started with bpmn-js

To begin, you need to install bpmn-js in your project. You can do this via npm:

npm install bpmn-js

Creating a BPMN Diagram

First, let’s create an instance of the bpmn-js modeler and load a simple BPMN diagram:

  import BpmnModeler from 'bpmn-js/lib/Modeler';
  
  const modeler = new BpmnModeler({
    container: '#canvas'
  });

  async function loadDiagram(diagramXml) {
    try {
      await modeler.importXML(diagramXml);
      console.log('Diagram loaded successfully');
    } catch (err) {
      console.error('Failed to load diagram:', err);
    }
  }

  const diagramXml = `
  
    
      
    
  `;

  loadDiagram(diagramXml);

Handling XML Export

To export the current diagram to BPMN XML format, you can use the following API:

  async function exportDiagram() {
    try {
      const { xml } = await modeler.saveXML({ format: true });
      console.log('Diagram XML:', xml);
    } catch (err) {
      console.error('Failed to save XML:', err);
    }
  }

Adding Custom Elements

You can also add custom elements to your diagram by using the create API:

  const elementFactory = modeler.get('elementFactory');
  const rootElement = modeler.get('canvas').getRootElement();

  const customShape = elementFactory.createShape({
    type: 'bpmn:Task'
  });

  modeler.get('modeling').createShape(customShape, { x: 300, y: 200 }, rootElement);

Styling Elements

To style BPMN elements, you might want to use the APIs for setting color:

  const elementRegistry = modeler.get('elementRegistry');
  const modeling = modeler.get('modeling');

  const taskElement = elementRegistry.get('Task_1');
  modeling.setColor(taskElement, {
    fill: 'yellow',
    stroke: 'black'
  });

Comprehensive Application Example

Now, let’s bring it all together in a simple BPMN modeler application:

  import BpmnModeler from 'bpmn-js/lib/Modeler';

  const xml = `
  ...

  function App() {
    const containerRef = useRef(null);

    useEffect(() => {
      const modeler = new BpmnModeler({
        container: containerRef.current
      });

      modeler.importXML(xml)
        .then(() => console.log('Diagram imported successfully'))
        .catch(err => console.error('Failed to import diagram:', err));
      
      // Export functionality
      async function exportDiagram() {
        try {
          const { xml } = await modeler.saveXML({ format: true });
          console.log('Exported Diagram XML:', xml);
        } catch (err) {
          console.error('Failed to export XML:', err);
        }
      }

      // Usage of other APIs (Creating Element, Changing colors, etc.)
      ...

    }, []);

    return (
      

        

        Export Diagram
      
    );
  }

  export default App;

This example showcases the use of bpmn-js to create, manipulate, and export BPMN diagrams, making it easier to understand and implement BPMN 2.0 standards in your applications.

With the above guide, you should be well-equipped to embark on your journey with bpmn-js and leverage its capabilities in your workflow automation projects.

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