String expression = taskListenerElement.attribute("expression");
String delegateExpression = taskListenerElement.attribute("delegateExpression");
Element scriptElement = taskListenerElement.elementNS(BpmnParser.ACTIVITI_BPMN_EXTENSIONS_NS, "script");
if (className != null) {
taskListener = new ClassDelegateTaskListener(className, parseFieldDeclarations(taskListenerElement));
} else if (expression != null) {
taskListener = new ExpressionTaskListener(expressionManager.createExpression(expression));
} else if (delegateExpression != null) {
taskListener = new DelegateExpressionTaskListener(expressionManager.createExpression(delegateExpression), parseFieldDeclarations(taskListenerElement));
}