Loot Table Generation

Loot tables can be generated for a mod by constructing a new LootTableProvider and providing LootTableProvider.SubProviderEntrys. The provider must be added to the DataGenerator.

// On the MOD event bus
@SubscribeEvent
public void gatherData(GatherDataEvent event) {
    event.getGenerator().addProvider(
        // Tell generator to run only when server data are generating
        event.includeServer(),
        output -> new LootTableProvider(
            output,
            // Specify registry names of tables that are required to generate, or can leave empty
            Collections.emptySet(),
            // Sub providers which generate the loot
            List.of(subProvider1, subProvider2, /*...*/),
            event.getLookupProvider()
        )
    );
}

LootTableSubProvider

Each LootTableProvider.SubProviderEntry takes in a supplied LootTableSubProvider, which generates the loot table, for a given LootContextParamSet. The LootTableSubProvider contains a method which takes in the lookup provider and a writer (BiConsumer<ResourceKey<LootTable>, LootTable.Builder>) to generate a table.

public class ExampleSubProvider implements LootTableSubProvider {

  // Used to create a factory method for the wrapping Supplier
  public ExampleSubProvider() {}

  // The method used to generate the loot tables
  @Override
  public void generate(HolderLookup.Provider lookupProvider, BiConsumer<ResourceKey<LootTable>, LootTable.Builder> writer) {
    // Generate loot tables here by calling writer#accept
  }
}

The table can then be added to LootTableProvider#getTables for any available LootContextParamSet:

// In the list passed into the LootTableProvider constructor
new LootTableProvider.SubProviderEntry(
  ExampleSubProvider::new,
  // Loot table generator for the 'empty' param set
  LootContextParamSets.EMPTY
)

BlockLootSubProvider and EntityLootSubProvider Subclasses

For LootContextParamSets#BLOCK and #ENTITY, there are special types (BlockLootSubProvider and EntityLootSubProvider respectively) which provide additional helper methods for creating and validating that there are loot tables.

The BlockLootSubProvider's constructor accepts a list of items that are explosion resistant to determine whether the loot table can be generated if a block is exploded, and a FeatureFlagSet, to determine whether the block is enabled so that a loot table is generated for it. Optionally, a map can be provided that contains initial block loot tables to generate.

// In some BlockLootSubProvider subclass
public MyBlockLootSubProvider() {
  super(Collections.emptySet(), FeatureFlags.REGISTRY.allFlags());
}

The EntityLootSubProvider's constructor takes in a FeatureFlagSet, which determines whether the entity type is enabled so that a loot table is generated for it. An optional FeatureFlagSet can be specified which determines which entity types must have a loot table to generate.

// In some EntityLootSubProvider subclass
public MyEntityLootSubProvider() {
  super(FeatureFlags.REGISTRY.allFlags());
}

To use them, all registered objects must be supplied to either BlockLootSubProvider#getKnownBlocks and EntityLootSubProvider#getKnownEntityTypes respectively. These methods are to make sure all objects within the iterable has a loot table.

tip

If DeferredRegister is being used to register a mod's objects, then the #getKnown* methods can be supplied the entries via DeferredRegister#getEntries:

// In some BlockLootSubProvider subclass for some DeferredRegister BLOCK_REGISTRAR
@Override
protected Iterable<Block> getKnownBlocks() {
  return BLOCK_REGISTRAR.getEntries() // Get all registered entries
    .stream() // Stream the wrapped objects
    .map(Holder::value) // Get the object if available
    .toList(); // Create the iterable
}

The loot tables themselves can be added by implementing the #generate method.

// In some BlockLootSubProvider subclass
@Override
public void generate() {
  // Add loot tables here
}

Loot Table Builders

To generate loot tables, they are accepted by the LootTableSubProvider as a LootTable.Builder. Afterwards, the specified LootContextParamSet is set in the LootTableProvider.SubProviderEntry and then built via #build. Before being built, the builder can specify entries, conditions, and modifiers which affect how the loot table functions.

note

The functionality of loot tables is so expansive that it will not be covered by this documentation in its entirety. Instead, a brief description of each component will be mentioned. The specific subtypes of each component can be found using an IDE. Their implementations will be left as an exercise to the reader.

LootTable

Loot tables are the base object and can be transformed into the required LootTable.Builder using LootTable#lootTable. The loot table can be built with a list of pools (via #withPool) applied in the order they are specified along with functions (via #apply) to modify the resulting items of those pools. A specific random sequence instance (via #setRandomSequence) can also be specified.

LootPool

Loot pools represents a group to perform operations and can generate a LootPool.Builder using LootPool#lootPool. Each loot pool can specify the entries (via #add) which define the operations in the pool, the conditions (via #when) which define if the operations in the pool should be performed, and functions (via #apply) to modify the resulting items of the entries. Each pool can be executed as many times as specified (via #setRolls). Additionally, bonus executions can be specified (via #setBonusRolls) which is modified by the luck of the executor.

LootPoolEntryContainer

Loot entries define the operations to occur when selected, typically generating items. Each entry has an associated, registered LootPoolEntryType. They also have their own associated builders which subtype LootPoolEntryContainer.Builder. Multiple entries can execute at the same time (via #append) or sequentially until one fails (via #then). Additionally, entries can default to another entry on failure (via #otherwise).

LootItemCondition

Loot conditions define requirements which need to be met for some operation to execute. Each condition has an associated, registered LootItemConditionType. They also have their own associated builders with subtype LootItemCondition.Builder. Loot conditions can be specified such that all conditions must return true (via #and, the default behavior), or that at least one condition must return true (via #or). Additionally, the resulting output of a condition can be inverted (via #invert).

LootItemFunction

Loot functions modify the result of an execution before passing it to the output. Each function has an associated, registered LootItemFunctionType. They also have their own associated builders which subtype LootItemFunction.Builder.

NbtProvider

NBT providers are a special type of functions defined by CopyCustomDataFunction. They define where to pull tag information from. Each provider has an associated, registered LootNbtProviderType.

NumberProvider

Number providers determine how many times a loot pool executes. Each provider has an associated, registered LootNumberProviderType.

ScoreboardNameProvider

Scoreboard providers are a special type of number providers defined by ScoreboardValue. They define the name of the scoreboard to pull the number of rolls to execute from. Each provider has an associated, registered LootScoreProviderType.