Chinese L (tourist) visa is designed for travellers who enter China for family visit and sightseeing. For family visit, your relatives in China should send you an invitation letter stating that they will sponsor you(accomodation and daily expenses, etc.). They should also leave their contact information (cell phone number, address) on the page of the invitation letter.) You'd better apply in person at the embassy.

Mr.Shane.. thank you very much for your prompt reply. I have one more question ; if there something necesary for me to show my return ticket or just one way flight to Shanghai beside the other docs required when applying the visa in Chinese Embassy -Jakarta.. ?
Thank you so much.

Better show the two-way flight tickets to the visa officers.