Creating parameter resolvers

The reason why your commands with method signatures like public void kick(GuildSlashEvent event, @AppOption User user, @AppOption String reason) works is because there are default parameter resolvers, they're registered automatically when ParameterResolvers is loaded. They can resolve regex command parameters / application command parameters and also button parameters

Creating a new ParameterResolver

To create a new parameter resolver, you have the following steps:

• Create a new class
• Make it extend ParameterResolver
• Use the super constructor to indicate the type of the resolved object
• Implement one or more of these interfaces described in ParameterResolver
• Register the resolver with ExtensionsBuilder#registerParameterResolver

Example - How to add a ParameterResolver

//Create the resolver
public class TimestampResolver extends ParameterResolver implements SlashParameterResolver {
	public TimestampResolver() {
		super(Timestamp.class);
	}

	@Override
	public Object resolve(@NotNull BContext context, @NotNull SlashCommandInfo info, @NotNull CommandInteractionPayload event, @NotNull OptionMapping optionMapping) {
		final Matcher timestampMatcher = MARKDOWN.matcher(optionMapping.getAsString());
		if (!timestampMatcher.find()) return null; //Avoid expensive exceptions from JDA

		final String format = timestampMatcher.group("style");
		final long time = Long.parseLong(timestampMatcher.group("time"));
		return (format == null ? DEFAULT : fromStyle(format)).atTimestamp(time);
	}

	@Override
	@NotNull
	public OptionType getOptionType() {
		return OptionType.STRING;
	}
}

Registering the parameter resolver

CommandsBuilder.newBuilder()
	.extensionsBuilder(extensionsBuilder ->
			extensionsBuilder.registerParameterResolver(new TimestampResolver())
	)
	.build(jda, "com.freya02.bot.wiki.paramresolver.commands");

Using these parameters

public class SlashParamResolverTest extends ApplicationCommand {
	@JDASlashCommand(name = "paramres")
	public void run(GuildSlashEvent event, @AppOption Timestamp timestamp) {
		event.reply("Your timestamp as relative: " + TimeFormat.RELATIVE.format(timestamp.getTimestamp())).queue();
	}
}