Make the spawning listen to the server spawn-settings

src/main/java/net/minecraft/server/EntityEgg.java

@@ -245,8 +245,12 @@ public class EntityEgg extends Entity {
                             break;
                     }
 
-                    entity.c(this.locX, this.locY, this.locZ, this.yaw, 0.0F);
-                    this.world.a(entity);
+                    // The world we're spawning in accepts this creature
+                    boolean isAnimal = entity instanceof EntityAnimal || entity instanceof EntityWaterAnimal;
+                    if ((isAnimal && this.world.L) || (!isAnimal && this.world.K)) {
+                        entity.c(this.locX, this.locY, this.locZ, this.yaw, 0.0F);
+                        this.world.a(entity);
+                    }
                 }
             }
             // CraftBukkit end

src/main/java/net/minecraft/server/TileEntityMobSpawner.java

@@ -49,6 +49,13 @@ public class TileEntityMobSpawner extends TileEntity {
                         return;
                     }
 
+                    // CraftBukkit start - The world we're spawning in accepts this creature
+                    boolean isAnimal = entityliving instanceof EntityAnimal || entityliving instanceof EntityWaterAnimal;
+                    if ((isAnimal && !this.a.L) || (!isAnimal && !this.a.K)) {
+                        return;
+                    }
+                    // CraftBukkit end
+
                     int j = this.a.a(entityliving.getClass(), AxisAlignedBB.b((double) this.b, (double) this.c, (double) this.d, (double) (this.b + 1), (double) (this.c + 1), (double) (this.d + 1)).b(8.0D, 4.0D, 8.0D)).size();
 
                     if (j >= 6) {

src/main/java/net/minecraft/server/World.java

@@ -61,8 +61,8 @@ public class World implements IBlockAccess {
     public boolean x;
     private ArrayList I = new ArrayList();
     private int J = 0;
-    private boolean K = true;
-    private boolean L = true;
+    public boolean K = true; // CraftBukkit private->public
+    public boolean L = true; // CraftBukkit private->public
     static int y = 0;
     private Set M = new HashSet();
     private int N;
@@ -1439,7 +1439,11 @@ public class World implements IBlockAccess {
     }
 
     public void f() {
-        SpawnerCreature.a(this, this.K, this.L);
+        // CraftBukkit start -- Only call spawner if we have players online and the world allows for mobs or animals
+        if ((this.K || this.L) && (this instanceof WorldServer && ((WorldServer) this).getServer().getHandle().b.size() > 0))
+            SpawnerCreature.a(this, this.K, this.L);
+        // CraftBukkit end
+
         this.G.a();
         int i = this.a(1.0F);
 

src/main/java/net/minecraft/server/WorldServer.java

@@ -47,9 +47,11 @@ public class WorldServer extends World implements BlockChangeDelegate {
     }
 
     public void a(Entity entity, boolean flag) {
-        if (!this.D.m && (entity instanceof EntityAnimal || entity instanceof EntityWaterAnimal)) {
-            entity.q();
-        }
+        // CraftBukkit start -- We prevent spawning in general, so this butching is not needed
+        //if (!this.D.m && (entity instanceof EntityAnimal || entity instanceof EntityWaterAnimal)) {
+        //    entity.q();
+        //}
+        // CraftBukkit end
 
         if (entity.passenger == null || !(entity.passenger instanceof EntityHuman)) {
             super.a(entity, flag);