This song-group has been widely discussed here in the past, as might be expected; and a great many references to these discussions and to texts in the Digital Tradition database can be found through the onsite search engines here; entering john barleycorn into the "Digitrad and Forum Search", which you will find on the main Forum page, will retrieve these (though not any that are entirely recent, as they will not yet have been indexed).I added a fairly long list of links to relevant material here and elsewhere in a "Penguin Book" thread some time ago; looking at them should keep you busy for a while.