LivingEntityMixin.java

package com.example.examplemod.mixin;

import net.minecraft.entity.LivingEntity;
import net.minecraft.entity.damage.DamageSource;
import net.minecraft.text.Text;
import org.spongepowered.asm.mixin.Mixin;
import org.spongepowered.asm.mixin.injection.At;
import org.spongepowered.asm.mixin.injection.Inject;
import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;

/**
 * Mixin into LivingEntity to add a "lucky dodge" chance that cancels damage.
 * Mixins are version-sensitive at the bytecode level but this mixin target
 * (damage(DamageSource, float)) has been stable across 1.21.7 - 1.21.11.
 *
 * Register in examplemod.mixins.json under "mixins": ["LivingEntityMixin"].
 */
@Mixin(LivingEntity.class)
public abstract class LivingEntityMixin {

    // Inject at HEAD of damage(), cancel the whole method if our condition is met.
    @Inject(method = "damage", at = @At("HEAD"), cancellable = true)
    private void examplemod$onDamage(DamageSource source, float amount,
                                      CallbackInfoReturnable<Boolean> cir) {
        LivingEntity self = (LivingEntity) (Object) this;

        // 5% chance to completely dodge any damage
        if (self.getRandom().nextFloat() < 0.05f) {
            if (!self.getWorld().isClient) {
                self.sendMessage(Text.literal("You dodged the attack!"));
            }
            cir.setReturnValue(false); // cancel damage, "false" = no damage applied
        }
    }
}