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Events are the primary way plugins interact with server and player actions. Paper’s event system allows you to listen for and respond to hundreds of different events.

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Event Basics

All events extend the org.bukkit.event.Event class and are called by the PluginManager.

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The Event Class

From org.bukkit.event.Event: 
public abstract class Event {
    private final boolean isAsync;

    public Event() {
        this(false);  // Synchronous by default
    }

    public Event(boolean isAsync) {
        this.isAsync = isAsync;
    }

    public abstract HandlerList getHandlers();
    
    public final boolean isAsynchronous() {
        return this.isAsync;
    }
}

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Creating an Event Listener

1

Create a Listener Class

Create a class that implements the Listener interface:
package com.example.myplugin;

import org.bukkit.event.Listener;
import org.bukkit.event.EventHandler;
import org.bukkit.event.player.PlayerJoinEvent;

public class MyListener implements Listener {

    @EventHandler
    public void onPlayerJoin(PlayerJoinEvent event) {
        event.getPlayer().sendMessage("Welcome to the server!");
    }
}
The Listener interface is a marker interface with no methods (from org.bukkit.event.Listener):
public interface Listener {}
2

Register the Listener

Register your listener in the plugin’s onEnable() method:
@Override
public void onEnable() {
    getServer().getPluginManager().registerEvents(new MyListener(), this);
}
The second parameter is your plugin instance, which is used to track which plugin registered the listener.

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The @EventHandler Annotation

The @EventHandler annotation marks methods as event handlers. From org.bukkit.event.EventHandler: 
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface EventHandler {
    EventPriority priority() default EventPriority.NORMAL;
    boolean ignoreCancelled() default false;
}

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Event Priority

Control the order in which your event handler is called: 
@EventHandler(priority = EventPriority.HIGH)
public void onPlayerJoin(PlayerJoinEvent event) {
    // This runs with HIGH priority
}
Priority order (from org.bukkit.event.EventPriority):
  1. LOWEST - Called first, for early modifications
  2. LOW - Called early
  3. NORMAL - Default priority
  4. HIGH - Called late
  5. HIGHEST - Called very late, final modifications
  6. MONITOR - Read-only, for observation (don’t modify events!)
@EventHandler(priority = EventPriority.LOWEST)
public void onDamage(EntityDamageEvent event) {
    // Runs first - good for canceling events early
    if (event.getEntity() instanceof Player) {
        event.setCancelled(true);
    }
}
The MONITOR priority should only be used for observing events, not modifying them. Changes made at this priority may not be respected by other plugins.

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Ignore Cancelled Events

Skip cancelled events with the ignoreCancelled parameter: 
@EventHandler(ignoreCancelled = true)
public void onBlockBreak(BlockBreakEvent event) {
    // This won't run if the event is cancelled by another plugin
}

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Common Events

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Player Events

Listen for player-related events: 
import org.bukkit.event.player.PlayerJoinEvent;
import org.bukkit.event.player.PlayerQuitEvent;
import org.bukkit.event.player.PlayerMoveEvent;
import org.bukkit.event.player.PlayerInteractEvent;

public class PlayerListener implements Listener {

    @EventHandler
    public void onJoin(PlayerJoinEvent event) {
        Player player = event.getPlayer();
        
        // Modify join message
        event.joinMessage(Component.text("Welcome " + player.getName()));
    }

    @EventHandler
    public void onQuit(PlayerQuitEvent event) {
        // Player is leaving
        savePlayerData(event.getPlayer());
    }

    @EventHandler
    public void onMove(PlayerMoveEvent event) {
        // Player moved
        // Be careful - this fires very frequently!
        if (event.getFrom().getBlock().equals(event.getTo().getBlock())) {
            return; // Only head movement, not position change
        }
    }
}

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PlayerJoinEvent Example

From org.bukkit.event.player.PlayerJoinEvent: 
public class PlayerJoinEvent extends PlayerEvent {
    private Component joinMessage;

    public @Nullable Component joinMessage() {
        return this.joinMessage;
    }

    public void joinMessage(@Nullable Component joinMessage) {
        this.joinMessage = joinMessage;
    }
}

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Block Events

import org.bukkit.event.block.BlockBreakEvent;
import org.bukkit.event.block.BlockPlaceEvent;

public class BlockListener implements Listener {

    @EventHandler
    public void onBlockBreak(BlockBreakEvent event) {
        Player player = event.getPlayer();
        Block block = event.getBlock();
        
        if (!player.hasPermission("myplugin.break")) {
            event.setCancelled(true);
            player.sendMessage("You don't have permission!");
        }
    }

    @EventHandler(priority = EventPriority.HIGHEST, ignoreCancelled = true)
    public void onBlockPlace(BlockPlaceEvent event) {
        // Only runs if no other plugin cancelled it
        awardPoints(event.getPlayer());
    }
}

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Entity Events

import org.bukkit.event.entity.EntityDamageEvent;
import org.bukkit.event.entity.EntityDeathEvent;

public class EntityListener implements Listener {

    @EventHandler
    public void onEntityDamage(EntityDamageEvent event) {
        if (event.getEntity() instanceof Player player) {
            // Player took damage
            if (isInSafeZone(player)) {
                event.setCancelled(true);
            }
        }
    }

    @EventHandler
    public void onEntityDeath(EntityDeathEvent event) {
        // Entity died
        event.getDrops().clear();  // Remove all drops
    }
}

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Cancellable Events

Many events can be cancelled to prevent the action from occurring: 
@EventHandler
public void onPlayerInteract(PlayerInteractEvent event) {
    if (event.getAction() == Action.RIGHT_CLICK_BLOCK) {
        if (event.getClickedBlock().getType() == Material.CHEST) {
            if (!event.getPlayer().hasPermission("myplugin.usechest")) {
                event.setCancelled(true);  // Prevent opening the chest
            }
        }
    }
}

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Calling Events

You can create and call custom events: 
// Create custom event
public class MyCustomEvent extends Event {
    private static final HandlerList HANDLER_LIST = new HandlerList();
    private final Player player;

    public MyCustomEvent(Player player) {
        this.player = player;
    }

    public Player getPlayer() {
        return player;
    }

    @Override
    public HandlerList getHandlers() {
        return HANDLER_LIST;
    }

    public static HandlerList getHandlerList() {
        return HANDLER_LIST;
    }
}

// Call the event
MyCustomEvent event = new MyCustomEvent(player);
getServer().getPluginManager().callEvent(event);
Or use the convenience method from the Event class: 
MyCustomEvent event = new MyCustomEvent(player);
boolean wasNotCancelled = event.callEvent();

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Asynchronous Events

Some events are fired asynchronously (off the main thread): 
@EventHandler
public void onAsyncChat(AsyncChatEvent event) {
    // This runs on a separate thread!
    // Be careful with thread safety
    
    if (event.isAsynchronous()) {  // Returns true
        // Don't call Bukkit API methods that aren't thread-safe
    }
}
Asynchronous event handlers must be thread-safe. Most Bukkit API methods should not be called from async events. Use Bukkit.getScheduler().runTask() to schedule tasks on the main thread if needed.

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Best Practices

  1. Use the correct priority:
    • LOWEST/LOW for early cancellation
    • NORMAL for most modifications
    • HIGH/HIGHEST for final modifications
    • MONITOR only for observation
  2. Check event state: 
    @EventHandler(ignoreCancelled = true)
public void onEvent(Event event) {
    // Automatically skips if cancelled
}
  3. Performance considerations: 
    @EventHandler
public void onPlayerMove(PlayerMoveEvent event) {
    // This fires VERY frequently - keep it fast!
    if (event.getFrom().getBlock().equals(event.getTo().getBlock())) {
        return;  // Only head movement, ignore
    }
}
  4. Unregister when done: 
    HandlerList.unregisterAll(listener);
  5. Use ignoreCancelled wisely:
    • Set to true when you don’t want to process cancelled events
    • Set to false when you need to see all events regardless of cancellation

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Event Reference

Common event packages:
  • org.bukkit.event.player.* - Player events
  • org.bukkit.event.block.* - Block events
  • org.bukkit.event.entity.* - Entity events
  • org.bukkit.event.inventory.* - Inventory events
  • org.bukkit.event.world.* - World events
  • org.bukkit.event.server.* - Server events
For a complete list, see the Paper API Javadocs.

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