Open Editor on Eclipse RCP

see that samples.
http://dev.eclipse.org/viewcvs/index.cgi/%7Echeckout%7E/platform-text-home/development/rcp/examples/index.html

that's difficult.
even in open text files,i should create some classes.
and now I'dont know how to use other editor plugin.
when i open file.
it coused that error
org.eclipse.ui.PartInitException: Text editor does not have a document provider

maybe on 3.1,that become more easy.