They live in China for years with an L visa?? Which kind of visa do they want to apply? If they still want to apply L-visa, tehy need to apply one through Chinese Visa Application Service Center in Jakarta. They should bring their passport and recently photo. You have to exit China every three months. For one year visa, they can also apply other kinds of visa, but it will need more requirements, for example invitation letter. For detailed information, you can ask for help at the consuular office.