Data fetching logic moved to separate funtion to make data re-fetching possible in case data have changed in server. Can't trigged for example by clicking on button or triggered by timer.
onSourceChanged was triggered 4 times when application was loaded that quite huge overhead. Added property active that should be changed to true when JSONLostModel component is loaded by with component element. I.e
JSONListModel {
  id: jmodel
  source: ...
  query: ...
  etc ..
  Component.onCompleted: active = true
}

example.qml also updated.