I have a block that's had an itemStackHandler, it contains 1 item that player inserts and rendering it on block.

I have done saving block load nbt data. But when i exiting and loading the world it only stores item on server side but not client.

So i need to get data from Server side inventory to Client side invenory, how can i do that?

My save/load code ->

@Override
    protected void saveAdditional(CompoundTag nbt) {
        nbt.put("inventory", itemStackHandler.serializeNBT());
        super.saveAdditional(nbt);
    }

    @Override
    public void load(CompoundTag nbt) { // TODO FIX MODEL RENDERING FOR CLIENT SIDE
        super.load(nbt);
        itemStackHandler.deserializeNBT(nbt.getCompound("inventory"));
    }

Render code ->

@Override
    public void render(SpecialCauldronBlockEntity entity, float pticks, PoseStack stack, MultiBufferSource buffer, int coverlay, int plight) {
        final BlockRenderDispatcher block_renderer = this.context.getBlockRenderDispatcher(); // TODO make block save items and render it

        //ItemStack item = Minecraft.getInstance().player.getMainHandItem();
        final ItemRenderer item_renderer = this.context.getItemRenderer();

        // Render Item inside

        if (state.getValue(HorizontalDirectionalBlock.FACING).equals(Direction.EAST) || state.getValue(HorizontalDirectionalBlock.FACING).equals(Direction.WEST)){
            stack.pushPose();
            stack.translate(0.5d, 0.55d, 0.5d);
            stack.scale(0.75f, 0.75f, 0.75f);
            stack.mulPose(Vector3f.YN.rotationDegrees(90));

            item_renderer.renderStatic(Minecraft.getInstance().player, entity.itemStackHandler.getStackInSlot(0), ItemTransforms.TransformType.FIXED, false, stack, buffer,
                    Minecraft.getInstance().level, coverlay, plight, plight);
            stack.popPose();
        } else {
            stack.pushPose();
            stack.translate(0.5d, 0.55d, 0.5d);
            stack.scale(0.75f, 0.75f, 0.75f);

            item_renderer.renderStatic(Minecraft.getInstance().player, entity.itemStackHandler.getStackInSlot(0), ItemTransforms.TransformType.FIXED, false, stack, buffer,
                    Minecraft.getInstance().level, coverlay, plight, plight);
            stack.popPose();
        }

 

https://forums.minecraftforge.net/topic/115679-1182-block-entity-renderer-disappears-after-leaving-the-world/#comment-511734

Thank you so much, it's now working!