Just two weeks after their season-ending Challenge Cup semi-final defeat at the hands of Sale, Connacht coach Michael Bradley has been a busy man.
With another ex-Leinster centre Jame Downey re-signing his contract and former fly-half Eric Elwood being named the province's assistant coach in recent weeks, Hearty's transer is another coup for the westerners.
Connacht CEO Gerry Kelly, who has also set his sights on former Ireland Under-21 captain David Gannon, a team mate of Hearty's at Blackrock, said: "John is a player we have had our eye on for some time, so it is good that the way is now clear for him to come and play for Connacht.
Hearty made his only appearance in a Leinster shirt against Ulster at Ravenhill in the Celtic League twelve months ago. 6ft 4in lock Gannon - who turned 22 in February - came on as a second half substitute against the Borders in January to make his Leinster bow.
Both Meagher and O'Brien, noted backs with AIB League Division One sides Buccaneers and Clontarf, were on development deals.