Minecraft wiki entry for Defeating_a_woodland_mansion, associated text: In Java Edition shields are redundant, so quickly attack them until they die.
Against a group, either strike before retreating, or build a 3-block tall pillar to hit your assailants from above.
They drop 0-2 emeralds upon death and have a chance of dropping their iron axe as well.
Try not to run into a group of vindicators because if each of them attack you it's easy to lose a lot of health.
If there are any hostile mobs such as zombies around you or the vindicator, quickly lure the zombies to the vindicator and name the vindicator "Johnny" with your name tags so you can attack the vindicator while it's attacking the zombies. That way you can easily dispatch the vindicator without it's attention entirely on you. Skeletons aren't a good idea, unless you make them accidently shoot the vindicator instead, which require good skills.
Using a bow to kill them is a good idea, you can also locate a vindicator, stay away from it, and build a 3-block tall pillar so you can snipe the vindicator from the top of the pillar. If your bow is enchanted with Flame or Power, you can snipe it from far away so it can kill the vindicator in one hit. If you miss, it doesn't matter. The vindicator doesn't care if a arrow sails over its head, so you can snipe it again until it dies.
The best strategy is attacking and running backwards so you can knock the vindicator away while running backwards, but be careful, vindicators can ambush you from behind if you don't pay attention to your surroundings.