Mob Goal API

The Mob Goal API is a way of controlling the behavior of mobs in Minecraft. It allows you to set a goal for a mob to perform, such as attacking a player, or moving to a location. It also allows you to create your own custom goals.

Adding a goal to an entity

To add a goal to an entity, you need to obtain an instance of the goal and then add it to the entity’s MobGoals:

Cow cow = ...;
Goal<Cow> goal = new ExampleGoal();

// 0 is the priority. A lower number denotes a higher priority.
server.getMobGoals().addGoal(cow, 0, goal);

Creating a custom goal

To create a custom goal, you need to create a class that implements the Goal interface. This interface has several methods:

void start(): Called when the goal is started.
void tick(): Called every tick while the goal is running.
void stop(): Called when the goal is stopped.
boolean shouldActivate(): Called to determine if the goal should start.
boolean shouldStayActive(): Called to determine if the goal should continue running.
GoalKey getKey(): Called to get the key for the goal.
EnumSet<GoalType> getTypes(): Called to get the types of the goal.

Here is an example of a goal that makes a camel follow a player. This is essentially the same as the FOLLOW_MOB Vanilla goal, but it is a good example of how to create a goal.

@NullMarked
public class CamelFollowPlayerGoal implements Goal<Camel> {

    // This is the key for the goal. It is used to identify the goal and is
    // used to determine if two goals are the same.
    public static final GoalKey<Camel> KEY = GoalKey.of(
        // The entity class this goal is targeting.
        Camel.class,
        // The key used for identification. Should use your plugin's namespace.
        new NamespacedKey("testplugin", "camel_follow_player")
    );

    private final Player player; // The player to follow.
    private final Camel camel; // The camel that is following.

    public CamelFollowPlayerGoal(Player player, Camel camel) {
        this.player = player;
        this.camel = camel;
    }

    @Override
    public boolean shouldActivate() {
        // Whether the goal should start. In this case, we want the goal to always
        // start so we return true. You could also return false if a specific
        // condition needs to be met.
        return true;
    }

    @Override
    public void start() {
        // Called when the goal starts.
        player.sendMessage(text("I am following you!"));
    }

    @Override
    public void tick() {
        // Called every tick while the goal is running. Here, we make the camel
        // move towards the player using the Pathfinder API.
        // The 5.0 is the speed of the camel.
        camel.getPathfinder().moveTo(player, 5.0);
    }

    @Override
    public void stop() {
        // Called when the goal stops.
        player.sendMessage(text("I stopped following you!"));
    }

    @Override
    public GoalKey<Camel> getKey() {
        return KEY;
    }

    @Override
    public EnumSet<GoalType> getTypes() {
        // Returns the types of this goal. Since we are changing the
        // camel's look direction and move it, we return MOVE and LOOK.
        // You may return as many types as you need.
        return EnumSet.of(GoalType.MOVE, GoalType.LOOK);
    }
}

Removing a goal

To remove a goal, you call one of the removeGoal method:

Cow cow = ...;

// This works because our example has a public static field.
server.getMobGoals().removeGoal(cow, CamelFollowPlayerGoal.KEY);

// You can also remove Vanilla goals.
server.getMobGoals().removeGoal(cow, VanillaGoal.TEMPT);

// Remove all goals with a MOVE type.
server.getMobGoals().removeAllGoals(cow, GoalType.MOVE);

// Remove all goals.
server.getMobGoals().removeAllGoals(cow);