Reject @Overwrite, return to interface

src/main/java/net/legacyfabric/abstractmethods/mixin/EnderDragonEntityMixin.java

@@ -0,0 +1,20 @@
+package net.legacyfabric.abstractmethods.mixin;
+
+import net.minecraft.entity.boss.BossBarProvider;
+import net.minecraft.entity.boss.dragon.EnderDragonEntity;
+import net.minecraft.entity.mob.MobEntity;
+import net.minecraft.text.Text;
+import net.minecraft.world.World;
+import org.spongepowered.asm.mixin.Mixin;
+
+@Mixin(EnderDragonEntity.class)
+public abstract class EnderDragonEntityMixin extends MobEntity implements BossBarProvider {
+    public EnderDragonEntityMixin(World world) {
+        super(world);
+    }
+
+    @Override
+    public Text title() {
+        return getName();
+    }
+}

src/main/java/net/legacyfabric/abstractmethods/mixin/WitherEntityMixin.java

@@ -0,0 +1,20 @@
+package net.legacyfabric.abstractmethods.mixin;
+
+import net.minecraft.entity.boss.BossBarProvider;
+import net.minecraft.entity.boss.WitherEntity;
+import net.minecraft.entity.mob.HostileEntity;
+import net.minecraft.text.Text;
+import net.minecraft.world.World;
+import org.spongepowered.asm.mixin.Mixin;
+
+@Mixin(WitherEntity.class)
+public abstract class WitherEntityMixin extends HostileEntity implements BossBarProvider {
+    public WitherEntityMixin(World world) {
+        super(world);
+    }
+
+    @Override
+    public Text title() {
+        return getName();
+    }
+}

src/main/resources/abstractmethods.mixins.json

@@ -1,13 +1,12 @@
 {
   "required": true,
-  "package": "net.legacyfabric.mixin",
+  "package": "net.legacyfabric.abstractmethods.mixin",
   "compatibilityLevel": "JAVA_8",
   "injectors": {
     "defaultRequire": 1
   },
   "mixins": [
-    "client.bossbar.BossBarMixin",
-    "client.bossbar.EnderDragonEntityRendererMixin",
-    "client.bossbar.WitherEntityRendererMixin"
+    "EnderDragonEntityMixin",
+    "WitherEntityMixin"
   ]
 }