Anvil Opener (1.7.2).java

    // https://github.com/Bukkit/CraftBukkit/blob/7e1ac0a77129b169704c1e222ff2deb3ab6cd2d2/src/main/java/net/minecraft/server/EntityPlayer.java#L596
    //Method to open an anvil inventory to a player
    public static void openAnvil(Player player, Inventory inventory){

        //Get our EntityPlayer
        EntityPlayer p = ((CraftPlayer) player).getHandle();

        //Create the AnvilContainer
        AnvilContainer container = new AnvilContainer(p);

        //Set the items to the items from the inventory given
        container.getBukkitView().getTopInventory().setItem(0, inventory.getItem(0));
        container.getBukkitView().getTopInventory().setItem(1, inventory.getItem(1));
        //container.getBukkitView().getTopInventory().setItem(2, inventory.getItem(2));

        //Counter stuff that the game uses to keep track of inventories
        int c = p.nextContainerCounter();

        //Send the packet
        p.playerConnection.sendPacket(new PacketPlayOutOpenWindow(c, 8, "Repairing", 9, true));

        //Set their active container to the container
        p.activeContainer = container;

        //Set their active container window id to that counter stuff
        p.activeContainer.windowId = c;

        //Add the slot listener
        p.activeContainer.addSlotListener(p);

    }