minecraft-plugin-dev

Minecraft Plugin Development Skill

Platform Overview

Paper is the recommended target. Paper includes all Bukkit and Spigot APIs plus significant performance improvements and additional APIs.

Routing Boundaries

• Use when: the target is server-side Paper/Bukkit/Spigot plugin behavior with JavaPlugin APIs.
• Do not use when: the task requires client-side installable mods or loader APIs (minecraft-modding / minecraft-multiloader).
• Do not use when: the task is pure vanilla datapack/command content (minecraft-datapack / minecraft-commands-scripting).

Bundled References

• Read references/runtime-patterns.md when the task touches scheduling, Folia support, PDC, Adventure/MiniMessage, YAML config, Vault, or Paper-specific APIs.
• Read references/paper-plugin-commands.md for a Paper-only paper-plugin.yml project or Brigadier command registration.

Project Setup

The examples below target current Paper 26.3 and Java 25. For an existing 1.21.x plugin, preserve its 1.21.x-R0.1-SNAPSHOT dependency, Java 21 toolchain, and matching api-version until the project is intentionally ported.

settings.gradle.kts

rootProject.name = "my-plugin"

build.gradle.kts

plugins {
    java
}

group = "com.example"
version = "1.0.0-SNAPSHOT"

repositories {
    mavenCentral()
    maven("https://repo.papermc.io/repository/maven-public/")
}

dependencies {
    compileOnly("io.papermc.paper:paper-api:26.3.build.+")
}

java {
    toolchain.languageVersion.set(JavaLanguageVersion.of(25))
}

tasks {
    processResources {
        // Substitutes ${version} in plugin.yml with the Gradle project version
        filesMatching(listOf("plugin.yml", "paper-plugin.yml")) {
            expand("version" to project.version)
        }
    }
}

Add Shadow only when the plugin has runtime libraries that must be bundled and relocated. Paper and optional plugin APIs such as Vault remain compileOnly and must not be shaded into the plugin JAR.

gradle/wrapper/gradle-wrapper.properties

distributionUrl=https\://services.gradle.org/distributions/gradle-9.1.0-bin.zip

Gradle 8.8 cannot run on Java 25. Use Gradle 9.1 or newer for a current Java 25 project. Preserve the existing wrapper and Java 21 toolchain for a legacy 1.21.x project unless its build is intentionally upgraded and verified.

Project Layout

my-plugin/
├── build.gradle.kts
├── settings.gradle.kts
├── gradle/
│   └── wrapper/
│       └── gradle-wrapper.properties
└── src/main/
    ├── java/com/example/myplugin/
    │   ├── MyPlugin.java          ← main class (extends JavaPlugin)
    │   ├── listeners/
    │   │   └── PlayerListener.java
    │   ├── commands/
    │   │   └── MyCommand.java
    │   └── managers/
    │       └── DataManager.java
    └── resources/
        ├── plugin.yml            ← Bukkit-compatible descriptor
        ├── paper-plugin.yml      ← active descriptor for a Paper plugin
        └── config.yml

Core Files

plugin.yml (Bukkit-compatible default)

name: MyPlugin
version: "${version}"
main: com.example.myplugin.MyPlugin
description: An example Paper plugin
author: YourName
website: https://github.com/example/my-plugin
api-version: '26.3'

commands:
  myplugin:
    description: Main plugin command
    usage: /myplugin <subcommand>
    permission: myplugin.use
    aliases: [mp]

permissions:
  myplugin.use:
    description: Allows use of /myplugin
    default: true
  myplugin.admin:
    description: Admin access
    default: op

Match api-version to the oldest Paper API the plugin intentionally supports. Current Paper examples use 26.3; legacy 1.21 and positive 1.21.<patch> values remain valid for older servers. A server older than the declared value refuses to load the plugin.

paper-plugin.yml (experimental Paper-only format)

Prefer plugin.yml for Bukkit-compatible plugins. Use paper-plugin.yml only when the JAR is intentionally Paper-only and needs Paper-plugin behavior such as bootstrapping, loaders, or classloading isolation. It can be the only descriptor, but is not a drop-in replacement: Paper plugins do not use a commands field or getCommand(...) registration. Read `references/paper-plugin-commands.md` for the paired descriptor, main class, and Brigadier lifecycle registration.

When one JAR ships both descriptors, keep their shared metadata and main class aligned. Do not combine the Paper-only sample with the Bukkit-compatible MyPlugin sample below.

Bukkit-compatible main class

package com.example.myplugin;

import com.example.myplugin.commands.MyCommand;
import com.example.myplugin.listeners.PlayerListener;
import org.bukkit.plugin.java.JavaPlugin;

public final class MyPlugin extends JavaPlugin {

    @Override
    public void onEnable() {
        saveDefaultConfig();

        // Register listeners
        getServer().getPluginManager().registerEvents(new PlayerListener(), this);

        // Register commands
        var cmd = getCommand("myplugin");
        if (cmd == null) {
            throw new IllegalStateException("myplugin command is missing from plugin.yml");
        }
        var handler = new MyCommand(this);
        cmd.setExecutor(handler);
        cmd.setTabCompleter(handler);

        getLogger().info("MyPlugin enabled!");
    }

    @Override
    public void onDisable() {
        getLogger().info("MyPlugin disabled.");
    }

}

Event Listeners

package com.example.myplugin.listeners;

import net.kyori.adventure.text.Component;
import net.kyori.adventure.text.format.NamedTextColor;
import org.bukkit.event.EventHandler;
import org.bukkit.event.EventPriority;
import org.bukkit.event.Listener;
import org.bukkit.event.entity.PlayerDeathEvent;
import org.bukkit.event.player.PlayerJoinEvent;
import org.bukkit.event.player.PlayerQuitEvent;

public class PlayerListener implements Listener {

    @EventHandler(priority = EventPriority.NORMAL)
    public void onPlayerJoin(PlayerJoinEvent event) {
        event.joinMessage(
            Component.text(event.getPlayer().getName() + " joined!", NamedTextColor.GREEN)
        );
    }

    @EventHandler
    public void onPlayerQuit(PlayerQuitEvent event) {
        event.quitMessage(
            Component.text(event.getPlayer().getName() + " left.", NamedTextColor.YELLOW)
        );
    }

    @EventHandler
    public void onPlayerDeath(PlayerDeathEvent event) {
        // Modify death message using Adventure components
        event.deathMessage(
            Component.text("☠ ", NamedTextColor.RED)
                .append(Component.text(event.getPlayer().getName(), NamedTextColor.WHITE))
                .append(Component.text(" died!", NamedTextColor.RED))
        );
    }
}

EventPriority order

LOWEST → LOW → NORMAL → HIGH → HIGHEST → MONITOR Use MONITOR for logging only (never modify outcome). On events that implement Cancellable, use ignoreCancelled = true unless you need cancelled events.

Cancellable events

@EventHandler
public void onBlockBreak(BlockBreakEvent event) {
    if (event.getPlayer().hasPermission("myplugin.break.deny")) {
        event.setCancelled(true);
        event.getPlayer().sendMessage(Component.text("You cannot break blocks!", NamedTextColor.RED));
    }
}

Commands

This section is for the plugin.yml path above. Its declared command enables getCommand("myplugin"). For a Paper-only descriptor, use the Brigadier lifecycle example in `references/paper-plugin-commands.md`.

package com.example.myplugin.commands;

import com.example.myplugin.MyPlugin;
import net.kyori.adventure.text.Component;
import net.kyori.adventure.text.format.NamedTextColor;
import org.bukkit.command.Command;
import org.bukkit.command.CommandExecutor;
import org.bukkit.command.CommandSender;
import org.bukkit.command.TabCompleter;
import org.bukkit.entity.Player;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import java.util.List;
import java.util.Locale;

public class MyCommand implements CommandExecutor, TabCompleter {

    private final MyPlugin plugin;

    public MyCommand(MyPlugin plugin) {
        this.plugin = plugin;
    }

    @Override
    public boolean onCommand(@NotNull CommandSender sender, @NotNull Command command,
                             @NotNull String label, @NotNull String[] args) {
        if (!(sender instanceof Player player)) {
            sender.sendMessage(Component.text("Only players can use this command.", NamedTextColor.RED));
            return true;
        }

        if (!player.hasPermission("myplugin.use")) {
            player.sendMessage(Component.text("No permission.", NamedTextColor.RED));
            return true;
        }

        if (args.length == 0) {
            player.sendMessage(Component.text("Usage: /myplugin <reload|info>", NamedTextColor.YELLOW));
            return true;
        }

        return switch (args[0].toLowerCase(Locale.ROOT)) {
            case "reload" -> {
                plugin.reloadConfig();
                player.sendMessage(Component.text("Config reloaded.", NamedTextColor.GREEN));
                yield true;
            }
            case "info" -> {
                player.sendMessage(Component.text("Version: " + plugin.getDescription().getVersion(), NamedTextColor.AQUA));
                yield true;
            }
            default -> {
                player.sendMessage(Component.text("Unknown subcommand.", NamedTextColor.RED));
                yield true;
            }
        };
    }

    @Override
    public @Nullable List<String> onTabComplete(@NotNull CommandSender sender, @NotNull Command command,
                                                @NotNull String label, @NotNull String[] args) {
        if (args.length == 1) {
            return List.of("reload", "info").stream()
                .filter(s -> s.startsWith(args[0].toLowerCase(Locale.ROOT)))
                .toList();
        }
        return List.of();
    }
}

Schedulers

For classic Paper plugins, BukkitScheduler is still fine. If you claim Folia support, route player, entity, region, global, and async work through the matching Folia-aware scheduler. Keep scheduling behind a small project-local interface when one plugin must support both Paper and Folia.

See references/runtime-patterns.md for copy-ready sync, async, cancelable, and Folia-safe scheduler examples.

Persistent Data Container (PDC)

PDC stores arbitrary data on any PersistentDataHolder (players, entities, items, chunks). Data is saved with the world and persists across restarts.

Create NamespacedKey instances once, keep data types stable after release, and use PDC for small metadata rather than large datasets. Prefer config files or a database for large or query-heavy plugin state.

See references/runtime-patterns.md for player, item, chunk, and world PDC examples.

Adventure Text Components

Paper uses Adventure natively for all text. No legacy chat colors. Use Component builders for code-owned messages and MiniMessage for config-driven messages. Avoid legacy ChatColor unless the target project already depends on it for compatibility.

See references/runtime-patterns.md for simple messages, hover/click events, MiniMessage parsing, titles, and action bars.

Configuration (YAML)

src/main/resources/config.yml

# Default config
settings:
  max-players: 20
  welcome-message: "<green>Welcome to the server!"
  cooldown-seconds: 30

database:
  host: localhost
  port: 3306
  name: myplugin_db

Accessing config values

Call saveDefaultConfig() in onEnable(), provide explicit defaults when reading values, and validate config shape before starting long-running tasks.

Custom config file

Use custom YAML files only when separating user config from mutable plugin data is worth the extra file handling. Keep blocking disk writes off hot event paths.

See references/runtime-patterns.md for config read/write and custom YAML examples.

Vault Integration (Economy / Permissions)

Declare Vault as compileOnly, soft-depend on it in plugin metadata, and disable economy features cleanly when the service provider is unavailable. Never assume a Vault-compatible economy plugin is installed just because Vault itself is present.

When Vault support is required, add the JitPack repository and compileOnly("com.github.MilkBowl:VaultAPI:1.7") to the Gradle build.

See references/runtime-patterns.md for a minimal economy setup and charge example.

Paper-Specific APIs

Use Paper APIs when they remove main-thread blocking or simplify Adventure-native behavior. Keep optional plugin integrations behind presence checks and metadata soft-dependencies.

See references/runtime-patterns.md for async chunk loading, custom item meta, profile lookup, and protection-plugin integration examples.

Common Tasks Checklist

Creating a new event listener

• [ ] Create class implementing Listener
• [ ] Annotate methods with @EventHandler
• [ ] Call getServer().getPluginManager().registerEvents(listener, plugin) in onEnable()
• [ ] On cancellable events, add ignoreCancelled = true unless you need cancelled events

Adding a new command

• [ ] For a Bukkit-compatible plugin, define the command in plugin.yml, create a CommandExecutor, and register it with getCommand("name")
• [ ] For a Paper-only plugin, register the command through LifecycleEvents.COMMANDS; do not add a commands field

Saving plugin data

• [ ] For simple values: use config.yml via getConfig() / saveConfig()
• [ ] For per-entity data: use PDC with a NamespacedKey
• [ ] For large datasets: use async scheduler + file I/O or a database

Scheduling a repeating task

• [ ] Determine if task needs main thread (use runTaskTimer) or is I/O (use runTaskTimerAsynchronously)
• [ ] Store the BukkitTask reference so you can cancel in onDisable()
• [ ] Cancel all tasks in onDisable() or use getServer().getScheduler().cancelTasks(plugin)

Build, Validate, and Run

1. Build the plugin JAR:

   ./gradlew build
   # Output: build/libs/my-plugin-1.0.0-SNAPSHOT.jar

1. Run the bundled validator to catch config and layout errors:

   ./scripts/validate-plugin-layout.sh --root /path/to/plugin-project
   # Strict mode treats warnings as failures:
   ./scripts/validate-plugin-layout.sh --root /path/to/plugin-project --strict

The validator requires Node and includes its own YAML parser for descriptor checks.

1. Fix any reported errors and re-run until clean.
2. Deploy: copy the built JAR to server/plugins/ and restart the Paper server.

If the real project already applies a Paper dev-server plugin such as xyz.jpenilla.run-paper, use that project's documented dev task instead of assuming ./gradlew runServer exists.

The validator checks:

• active plugin.yml or paper-plugin.yml required keys (name, version, main, api-version) and repo-supported current 26.<release> or legacy 1.21 / positive 1.21.<patch> values, with warnings for versions newer than the documented examples
• cross-descriptor metadata consistency when both descriptors are present; paper-plugin.yml is selected as active
• Active main class path exists and extends JavaPlugin
• actual server /reload anti-patterns such as Bukkit.reload() or dispatching the server reload command

References

• Paper API Javadoc: https://jd.papermc.io/paper/
• Paper plugin descriptor: https://docs.papermc.io/paper/dev/plugin-yml/
• Paper plugins: https://docs.papermc.io/paper/dev/getting-started/paper-plugins/
• Paper Brigadier registration: https://docs.papermc.io/paper/dev/command-api/basics/registration/
• Gradle Java compatibility: https://docs.gradle.org/current/userguide/compatibility.html
• Adventure (text API): https://docs.advntr.dev/
• MiniMessage format: https://docs.advntr.dev/minimessage/format.html
• Vault API: https://github.com/MilkBowl/VaultAPI
• Bukkit API Javadoc: https://javadoc.io/doc/org.bukkit/bukkit/
• run-task Gradle plugin: https://github.com/jpenilla/run-task