Johnson, who will turn 20 next month, finished tied for third on the Windsor Spitfires of the Ontario Hockey League this season with 53 points (28 goals) in 59 games. The 6-foot, 190-pound forward led the Spitfires with four goals and six points during the 2014 OHL playoffs and then joined Albany of the American Hockey League upon completion of his junior season.
Johnson, a third-round pick (No. 90) in the 2012 NHL Draft, had 66 goals and 128 points in 191 games during his junior career.
Thomson, 21, split the 2013-14 season between Kitchener (12 games) and North Bay (43) of the OHL. The 6-3, 215-pound forward had 27 goals, 45 points and 90 penalty minutes in the regular season and five goals and 14 points in 22 playoff games.
Thomson, a fourth-round pick (No. 96) in 2012, has career totals of 65 goals, 149 points and 483 penalty minutes in five OHL seasons.
In other signings Friday:
Kiviaho, 20, was a fifth-round pick (No. 144) in the 2012 draft. A native of Lappeenranta, Finland, he split this season between KalPa of Finland's SM-Liiga and their Junior A program. In the SM-Liiga, he appeared in 13 games recording a 2.92 goals-against average and a .881 save percentage. In three postseason games, he posted a 4.24 GAA and a .843 save percentage.