I'm making a chair that I can sit on right now, and I wrote the following code with reference to the startSleeping of the bed, but I get an error. I don't know the cause. Probably a DataParameter. After this, I want to use EXPANSIONMOD_POSE and CHAIR_POTISION, so I want to use this. If it can't be used, is there any alternative?
Note that the idea of using a mountable entity in the first place is not appropriate because you want to pose when sitting or make more complicated movements.

public class ExpansionModEntity extends Entity{
	public ExpansionModEntity(EntityType<?> entityTypeIn, World worldIn) {
		super(entityTypeIn, worldIn);
	}

	protected static final DataParameter<ExpansionModPose> EXPANSIONMOD_POSE = EntityDataManager.createKey(ExpansionModEntity.class, ExpansionModDataSerializers.EXPANSIONMOD_POSE);
	private static final DataParameter<Optional<BlockPos>> CHAIR_POSITION = EntityDataManager.createKey(ExpansionModEntity.class, DataSerializers.OPTIONAL_BLOCK_POS);

	public void setPose(ExpansionModPose poseIn) {
		this.dataManager.set(EXPANSIONMOD_POSE, poseIn);
	}

	private void setSittingPosition(BlockPos pos) {
		this.setPosition(pos.getX() + 0.5, pos.getY(), pos.getZ() + 0.5);
	}

	public Optional<BlockPos> getChairPosition() {
		return this.dataManager.get(CHAIR_POSITION);
	}

	public void setChairPosition(BlockPos pos) {
		this.dataManager.set(CHAIR_POSITION, Optional.of(pos));
	}

	public void clearChairPosition() {
		this.dataManager.set(CHAIR_POSITION, Optional.empty());
	}

	public void startSitting(BlockPos pos) {
		if (this.isPassenger()) {
			this.stopRiding();
		}

		this.setPose(ExpansionModPose.SITTING);
		this.setSittingPosition(pos);
		this.setChairPosition(pos);
	}

	@Override
	protected void registerData() {
	}

	@Override
	protected void readAdditional(CompoundNBT compound) {
	}

	@Override
	protected void writeAdditional(CompoundNBT compound) {
	}

	@Override
	public IPacket<?> createSpawnPacket() {
		return null;
	}
}

public class ChairBlock extends Block implements IWaterLoggable{
	public static final DirectionProperty FACING = HorizontalBlock.HORIZONTAL_FACING;
	public static final BooleanProperty WATERLOGGED = BlockStateProperties.WATERLOGGED;

	public static final VoxelShape BASE = VoxelShapes.or(
			Block.makeCuboidShape(2, 8, 2, 14, 10, 14),
			Block.makeCuboidShape(2, 0, 2, 4, 8, 4),
			Block.makeCuboidShape(2, 0, 12, 4, 8, 14),
			Block.makeCuboidShape(12, 0, 12, 14, 8, 14),
			Block.makeCuboidShape(12, 0, 2, 14, 8, 4)
		);
	public static final VoxelShape SHAPE_NORTH = VoxelShapes.or(
			BASE,
			Block.makeCuboidShape(2, 10, 12, 14, 18, 14)
	);
	public static final VoxelShape SHAPE_EAST = VoxelShapes.or(
			BASE,
			Block.makeCuboidShape(2, 10, 2, 4, 18, 14)
	);
	public static final VoxelShape SHAPE_SOUTH = VoxelShapes.or(
			BASE,
			Block.makeCuboidShape(2, 10, 2, 14, 18, 4)
	);
	public static final VoxelShape SHAPE_WEST = VoxelShapes.or(
			BASE,
			Block.makeCuboidShape(12, 10, 2, 14, 18, 14)
	);

	public ChairBlock(Properties properties) {
		super(properties);
		this.setDefaultState(this.stateContainer.getBaseState()
				.with(FACING, Direction.NORTH)
				.with(WATERLOGGED, false)
		);
	}

	@Override
	public BlockState getStateForPlacement(BlockItemUseContext context) {
		return this.getDefaultState()
				.with(FACING, context.getPlacementHorizontalFacing().getOpposite());
	}

	@SuppressWarnings("deprecation")
	public FluidState getFluidState(BlockState state) {
		return state.get(WATERLOGGED) ? Fluids.WATER.getStillFluidState(false) : super.getFluidState(state);
	}

	@Override
	protected void fillStateContainer(StateContainer.Builder<Block, BlockState> builder) {
		builder.add(
				FACING,
				WATERLOGGED
		);
	}

	@Override
	public VoxelShape getShape(BlockState state, IBlockReader worldIn, BlockPos pos, ISelectionContext context) {
		switch (state.get(FACING)) {
			case NORTH:
				return SHAPE_NORTH;
			case SOUTH:
				return SHAPE_SOUTH;
			case EAST:
				return SHAPE_EAST;
			case WEST:
				return SHAPE_WEST;
			default:
				return SHAPE_NORTH;
		}
	}

	@Override
	public ActionResultType onBlockActivated(BlockState state, World worldIn, BlockPos pos, PlayerEntity player, Hand handIn, BlockRayTraceResult hit) {
		ExpansionModEntity expansionModEntity = new ExpansionModEntity(EntityType.PLAYER, worldIn);
		expansionModEntity.startSitting(pos);
		return null;

		//return SeatEntity.create(worldIn, pos, 0.4, player);
	}
}

 

So, after that, read the vanilla code a little and protect protected static final DataParameter <ExpansionModPose> EXPANSIONMOD_POSE = EntityDataManager.createKey (ExpansionModEntity.class, ExpansionModDataSerializers.EXPANSIONMOD_POSE); protected static final DataParameter <ExpansionModPose> EXPANSIONMOD_POSE = EntityDataManager.create I rewrote it to .EXPANSIONMOD_POSE) ;, but found that I needed to add it with register in order to apply the dataManager to the player. Does this need to replace the vanilla player?