Traps

A trap is a block set on the ground that, after a while, closes on a creature: the player comes back and collects it. What it can catch is data, so an addon writes a trap block and a few JSON files.

Declaring a trap

public static final RegistryObject<TrapBlock> TRAPS = MyRegistry.REGISTRY.registerBlock("Traps",
        () -> new TrapBlock(BlockBehaviour.Properties.of().mapColor(MapColor.WOOD).strength(0.5F).noOcclusion(),
                2400, 6000,           // waits 2 to 5 minutes
                true,                 // single use: gone once its catch is collected
                MyProfessions.HUNTER  // optional: only a Hunter sets and collects it (Solo mode: anyone)
        ));

TrapBlock has a facing and a caught state: give it a model for each (open, and closed on its catch). One AkumaLib block entity type serves every addon's traps.

• Set on sturdy ground, it counts down a random delay in its range, then picks a catch. If nothing lives there, it waits another delay.
• On a catch it switches to caught=true with a sound. A right-click collects it: the creature is made, its variant rolled, and it goes through CatchableCreature.capture with the trap as the tool, so its capture loot table, CreatureCaptureEvent (your XP) and the akumalib:creature_capture advancement trigger all apply.
• Empty: "Nothing in the trap yet." Refused by the creature's canBeCapturedWith: "It got away from the trap." Wrong profession: "Only a %s can use this trap." (placement refused too). Creative players always can.

What a trap catches

data/mymod/trapping/seagull.json

{
  "entity": "mymod:seagull",
  "weight": 10,
  "biomes": ["#minecraft:is_beach", "#minecraft:is_ocean", "minecraft:stony_shore"],
  "requires_sky": true,
  "traps": ["mymod:traps"]
}

Field	Default	Meaning
entity	required	a CatchableCreature
weight	10	against the other catches possible at the same trap
biomes	anywhere	ids or #tags
requires_sky	false	"outside": nothing solid above the trap (leaves allowed: under a tree is outside)
traps	any trap	the trap blocks that can make this catch (an enhanced trap for rarer creatures)

TrapCatches.pick(level, pos, block, random) is what the trap calls, if you need it elsewhere.