Resources and data

Packs in the mod jar

assets/ in the mod jar is added automatically as a client resource pack, and data/ as a server data pack.

• The pack ID is poly/<mod id>.
• It is a required pack and sits on top of vanilla.
• The format is the same as vanilla 26.2.

Path	Purpose
assets/<mod>/blockstates/<block>.json, models/block/…, textures/block/…	Block appearance
assets/<mod>/items/<item>.json, models/item/…, textures/item/…	Item appearance
assets/<mod>/lang/en_us.json, ko_kr.json	block.<mod>.<id>, item.<mod>.<id>, key.<mod>.<id>, key.category.<mod>.keybinds
assets/<mod>/textures/entity/…	Mob textures
assets/<mod>/sounds.json	Sound events
assets/<mod>/particles/<path>.json, textures/particle/…	Particle sprites
assets/<mod>/post_effect/<path>.json, shaders/post/…	Post-processing shaders
data/<mod>/loot_table/blocks/<block>.json	Block drops (nothing drops if missing)
data/<mod>/recipe/*.json	Recipes
data/<mod>/advancement/*.json	Advancements
data/<mod>/worldgen/…, dimension/…, dimension_type/…, damage_type/…	World generation, dimensions, damage types
data/minecraft/tags/block/mineable/pickaxe.json ("replace": false)	Tool tags

data/my_mod/loot_table/blocks/glow_block.json

{
  "type": "minecraft:block",
  "pools": [
    {
      "rolls": 1.0,
      "conditions": [{"condition": "minecraft:survives_explosion"}],
      "entries": [{"type": "minecraft:item", "name": "my_mod:glow_block"}]
    }
  ]
}

Reload listeners

Use these when your mod reads data files in its own format.

mod.resources().onDataReload("my_mod/spells", files -> { /* … */ });    // data/<ns>/my_mod/spells/**.json
mod.resources().onAssetReload("my_mod/tips", files -> { /* … */ });     // assets/… (client)
mod.resources().onDataFiles("my_mod/banners", ".txt", files -> { /* … */ });   // received as bytes; onAssetFiles exists too

• onDataReload and onAssetReload give you JSON files as a Map<ResourceId, String>. onDataFiles and onAssetFiles give you files with the extension you specify as a Map<ResourceId, byte[]>.
• A file ID is <namespace>:<path under the directory>, and the pack with the higher priority wins.
• Server data: read at startup and on /reload, after the game data. It is called on the main thread at startup and on the server thread on /reload.
• Client assets: read on the client thread at startup and on F3+T.
• If a file cannot be read or a listener fails, Poly Mod Loader logs POLY-RESOURCE-003 and continues.

If you read the result from another thread, publish it by replacing a volatile field as a whole.

static volatile Map<ResourceId, String> messages = Map.of();

mod.resources().onDataReload("my_mod_messages", files -> messages = files);

Error codes

Code	Meaning
POLY-RESOURCE-001	Invalid reload directory
POLY-RESOURCE-002	Declared after registration closed
POLY-RESOURCE-003	File could not be read or listener failed (logged, then continues)
POLY-CONTENT-004	Unknown pack type