public void executeActivity(ProcessInstance instance) throws Exception{
final String actualContent = evaluateContent(instance, getContents()).toString();
if (getToRole() == null) {
throw new UEngineException("Receiver is not set.");
}
RoleMapping roleMapping = getToRole().getMapping(instance, getTracingTag());
if (roleMapping == null) {
throw new UEngineException("Actual target receiver is not set yet.");
}
String nateOnId = roleMapping.getExtendedProperty(EXT_PROP_KEY_NateOnMessengerId);
if (nateOnId == null) {