Hi Jerry Cui,
you can fetch the data in do_init_context method for displaying default values when ever your login into web ui the data will displayed in your table view.
just fallow Dharmakasi approch what he said you can achieve your requirement
see this logic for your reference purpose..
here i have used the standard structure that i have converted into collection assign to the node level..
just go through this link..
SAP CRM WEB UI : 57.VALUE NODE - DISPLAYING CUSTOM TABLE ON WEB UI
Srinivas.