Commands

In general, you should prefer to implement Brigadier / commands, but there are some cases where some additional flexibility is required.

Creating commands

Creating new commands is easy, you'll have to implement the Command interface, create a MapCodec to serialize/deserialize the command and register the codec with CommandTypes.register().

Let's create a simple command which will print a string to standard output.

public record DummyCommand(String text) implements Command {

    @Override
    public boolean execute(EventContext context) {
        System.out.println(text());
        return true; //Return if execution was successful.
    }

    @Override
    public CommandType type() {
        return null;
    }
}

Now create a Codec for your command.

public static final MapCodec<DummyCommand> CODEC = Codec.STRING.fieldOf("text").xmap(DummyCommand::new, DummyCommand::text);

With that done, we'll have to register the command to get our CommandType.

public static final CommandType DUMMY = CommandType.register(new Identifier("modid", "print"), DummyCommand.CODEC);

Now return this type in type().

@Override
public CommandType type() {
    return MyModInit.DUMMY;
}

EventContext

EventContext allows you to retrieve the LootContext which is passed with the event type.

context.lootContext().getWorld(); //Returns a ServerWorld.

context.lootContext().get(LootContextParameters.TOOL); //Returns the prameter or null if not present.

context.lootContext().requireParameter(LootContextParameters.TOOL); //Returns the parameter or throws an exception if not present.