When BlockDispenseEvent triggers, it appears that the dispenser inventory has already changed, even though BlockDispenseEvent is a cancellable event.

For example:

protected void onBlockDispense(BlockDispenseEvent event) {
BlockData blockData = event.getBlock().getBlockData();
ItemStack item = event.getItem();
  if (item != null && blockData instanceof Dispenser) {
    Location location = event.getBlock().getLocation();
    InventoryHolder inventoryHolder = (InventoryHolder) location.getBlock().getState();
    for (ItemStack item : inventoryHolder.getInventory().getContents()) {
      System.out.println(item.getType().name());
    }
  }
}

With that code, the dispensed item won't be displayed in the output. There is one exception though, being that if a water bucket or lava bucket is being dispensed, it still shows as being in the dispenser. I assume this is because the item is being changed from, for example, a water bucket to a regular bucket. However, it still shows the original item (e.g. a water bucket).

Expected behaviour is that all items should still show up as being in the dispenser for the event, not just water and lava buckets.