} else if (expression != null) {
executionListener = new ExpressionExecutionListener(expressionManager.createExpression(expression));
} else if (delegateExpression != null) {
executionListener = new DelegateExpressionExecutionListener(expressionManager.createExpression(delegateExpression), parseFieldDeclarations(executionListenerElement));
} else if (scriptElement != null) {
ExecutableScript executableScript = parseCamundaScript(scriptElement);
if (executableScript != null) {
executionListener = new ScriptExecutionListener(executableScript);
}
} else {
addError("Element 'class', 'expression', 'delegateExpression' or 'script' is mandatory on executionListener", executionListenerElement);