Extension attribute delegateExpression defined for a ServiceTask is lost while using BpmnXMLConverter

[janslee]

Describe the bug
When using the BpmnXMLConverter to convert a BpmnModel to XML, I defined a delegateExpression for the servicetask element, but it is lost during the conversion process,

Expected behavior
conversion process can convert the delegateExpression attribute

Code
BpmnModel model = new BpmnModel();
Process process = new Process();
...
flowElement = new ServiceTask();
...
ExtensionAttribute extensionAttribute = new ExtensionAttribute();
extensionAttribute.setNamespace(BpmnXMLConstants.FLOWABLE_EXTENSIONS_NAMESPACE);
extensionAttribute.setNamespacePrefix(BpmnXMLConstants.FLOWABLE_EXTENSIONS_PREFIX);
extensionAttribute.setName("delegateExpression");
extensionAttribute.setValue("${" + delegateExpression + "}");
flowElement.addAttribute(extensionAttribute);

      BpmnAutoLayout bpmnLayout = new BpmnAutoLayout(model); //debug can see the delegateExpression attribute
        bpmnLayout.execute();
        // convert to xml
        BpmnXMLConverter converter = new BpmnXMLConverter();
        xmlBytes = converter.convertToXML(model, "UTF-8");
        String xmlString = new String(xmlBytes, "UTF-8");  //missing the delegateExpression attribute in XML

Additional context
flowable version: 6.8.1, using mysql database, spring boot:2.7.18

[filiphr]

Hey @janslee,

Some attributes are treated specially by Flowable. In order to achieve what you are looking for you should not use an extension attribute. Rather use the setters on the ServiceTask itself.

e.g.

ServiceTask serviceTask = new ServiceTask();
serviceTask.setImplementationType(ImplementationType.IMPLEMENTATION_TYPE_DELEGATEEXPRESSION);
serviceTask.setImplementation("${" + delegateExpression + "}");

Doing it this way should export the delegate expression attribute in the XML.

[janslee]

Thanks a lot!you da man, it works perfectly