Final touches and recap#

There is one more improvement that we can make to our application. Currently, we utilize both the SQLAlchemyInitPlugin and the SQLAlchemySerializationPlugin, but there is a shortcut for this configuration: the SQLAlchemyPlugin is a combination of the two, so we can simplify our configuration by using it instead.

Here is our final application:

 1from typing import AsyncGenerator, List, Optional
 2
 3from advanced_alchemy.extensions.litestar.plugins.init.config.asyncio import autocommit_before_send_handler
 4from sqlalchemy import select
 5from sqlalchemy.exc import IntegrityError, NoResultFound
 6from sqlalchemy.ext.asyncio import AsyncSession
 7from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
 8
 9from litestar import Litestar, get, post, put
10from litestar.contrib.sqlalchemy.plugins import SQLAlchemyAsyncConfig, SQLAlchemyPlugin
11from litestar.exceptions import ClientException, NotFoundException
12from litestar.status_codes import HTTP_409_CONFLICT
13
14
15class Base(DeclarativeBase):
16    ...
17
18
19class TodoItem(Base):
20    __tablename__ = "todo_items"
21
22    title: Mapped[str] = mapped_column(primary_key=True)
23    done: Mapped[bool]
24
25
26async def provide_transaction(db_session: AsyncSession) -> AsyncGenerator[AsyncSession, None]:
27    try:
28        async with db_session.begin():
29            yield db_session
30    except IntegrityError as exc:
31        raise ClientException(
32            status_code=HTTP_409_CONFLICT,
33            detail=str(exc),
34        ) from exc
35
36
37async def get_todo_by_title(todo_name, session: AsyncSession) -> TodoItem:
38    query = select(TodoItem).where(TodoItem.title == todo_name)
39    result = await session.execute(query)
40    try:
41        return result.scalar_one()
42    except NoResultFound as e:
43        raise NotFoundException(detail=f"TODO {todo_name!r} not found") from e
44
45
46async def get_todo_list(done: Optional[bool], session: AsyncSession) -> List[TodoItem]:
47    query = select(TodoItem)
48    if done is not None:
49        query = query.where(TodoItem.done.is_(done))
50
51    result = await session.execute(query)
52    return result.scalars().all()
53
54
55@get("/")
56async def get_list(transaction: AsyncSession, done: Optional[bool] = None) -> List[TodoItem]:
57    return await get_todo_list(done, transaction)
58
59
60@post("/")
61async def add_item(data: TodoItem, transaction: AsyncSession) -> TodoItem:
62    transaction.add(data)
63    return data
64
65
66@put("/{item_title:str}")
67async def update_item(item_title: str, data: TodoItem, transaction: AsyncSession) -> TodoItem:
68    todo_item = await get_todo_by_title(item_title, transaction)
69    todo_item.title = data.title
70    todo_item.done = data.done
71    return todo_item
72
73
74db_config = SQLAlchemyAsyncConfig(
75    connection_string="sqlite+aiosqlite:///todo.sqlite",
76    metadata=Base.metadata,
77    create_all=True,
78    before_send_handler=autocommit_before_send_handler,
79)
80
81app = Litestar(
82    [get_list, add_item, update_item],
83    dependencies={"transaction": provide_transaction},
84    plugins=[SQLAlchemyPlugin(db_config)],
85)

 1from typing import Optional
 2from collections.abc import AsyncGenerator
 3
 4from advanced_alchemy.extensions.litestar.plugins.init.config.asyncio import autocommit_before_send_handler
 5from sqlalchemy import select
 6from sqlalchemy.exc import IntegrityError, NoResultFound
 7from sqlalchemy.ext.asyncio import AsyncSession
 8from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
 9
10from litestar import Litestar, get, post, put
11from litestar.contrib.sqlalchemy.plugins import SQLAlchemyAsyncConfig, SQLAlchemyPlugin
12from litestar.exceptions import ClientException, NotFoundException
13from litestar.status_codes import HTTP_409_CONFLICT
14
15
16class Base(DeclarativeBase):
17    ...
18
19
20class TodoItem(Base):
21    __tablename__ = "todo_items"
22
23    title: Mapped[str] = mapped_column(primary_key=True)
24    done: Mapped[bool]
25
26
27async def provide_transaction(db_session: AsyncSession) -> AsyncGenerator[AsyncSession, None]:
28    try:
29        async with db_session.begin():
30            yield db_session
31    except IntegrityError as exc:
32        raise ClientException(
33            status_code=HTTP_409_CONFLICT,
34            detail=str(exc),
35        ) from exc
36
37
38async def get_todo_by_title(todo_name, session: AsyncSession) -> TodoItem:
39    query = select(TodoItem).where(TodoItem.title == todo_name)
40    result = await session.execute(query)
41    try:
42        return result.scalar_one()
43    except NoResultFound as e:
44        raise NotFoundException(detail=f"TODO {todo_name!r} not found") from e
45
46
47async def get_todo_list(done: Optional[bool], session: AsyncSession) -> list[TodoItem]:
48    query = select(TodoItem)
49    if done is not None:
50        query = query.where(TodoItem.done.is_(done))
51
52    result = await session.execute(query)
53    return result.scalars().all()
54
55
56@get("/")
57async def get_list(transaction: AsyncSession, done: Optional[bool] = None) -> list[TodoItem]:
58    return await get_todo_list(done, transaction)
59
60
61@post("/")
62async def add_item(data: TodoItem, transaction: AsyncSession) -> TodoItem:
63    transaction.add(data)
64    return data
65
66
67@put("/{item_title:str}")
68async def update_item(item_title: str, data: TodoItem, transaction: AsyncSession) -> TodoItem:
69    todo_item = await get_todo_by_title(item_title, transaction)
70    todo_item.title = data.title
71    todo_item.done = data.done
72    return todo_item
73
74
75db_config = SQLAlchemyAsyncConfig(
76    connection_string="sqlite+aiosqlite:///todo.sqlite",
77    metadata=Base.metadata,
78    create_all=True,
79    before_send_handler=autocommit_before_send_handler,
80)
81
82app = Litestar(
83    [get_list, add_item, update_item],
84    dependencies={"transaction": provide_transaction},
85    plugins=[SQLAlchemyPlugin(db_config)],
86)

Recap#

In this tutorial, we have learned how to use the SQLAlchemy plugin to create a simple application that uses a database to store and retrieve data.

In the final application TodoItem is defined, representing a TODO item. It extends from the DeclarativeBase class provided by SQLAlchemy:

1class Base(DeclarativeBase):
2    ...
3
4
5class TodoItem(Base):
6    __tablename__ = "todo_items"
7
8    title: Mapped[str] = mapped_column(primary_key=True)
9    done: Mapped[bool]

Next, we define a dependency that centralizes our database transaction management and error handling. This dependency depends on the db_session dependency, which is provided by the SQLAlchemy plugin, and is made available to our handlers via the transaction argument:

1async def provide_transaction(db_session: AsyncSession) -> AsyncGenerator[AsyncSession, None]:
2    try:
3        async with db_session.begin():
4            yield db_session
5    except IntegrityError as exc:
6        raise ClientException(
7            status_code=HTTP_409_CONFLICT,
8            detail=str(exc),

We also define a couple of utility functions, that help us to retrieve our TODO items from the database:

 1async def get_todo_by_title(todo_name, session: AsyncSession) -> TodoItem:
 2    query = select(TodoItem).where(TodoItem.title == todo_name)
 3    result = await session.execute(query)
 4    try:
 5        return result.scalar_one()
 6    except NoResultFound as e:
 7        raise NotFoundException(detail=f"TODO {todo_name!r} not found") from e
 8
 9
10async def get_todo_list(done: Optional[bool], session: AsyncSession) -> List[TodoItem]:
11    query = select(TodoItem)
12    if done is not None:
13        query = query.where(TodoItem.done.is_(done))
14
15    result = await session.execute(query)
16    return result.scalars().all()

We define our route handlers, which are the interface through which TODO items can be created, retrieved and updated:

 1@get("/")
 2async def get_list(transaction: AsyncSession, done: Optional[bool] = None) -> List[TodoItem]:
 3    return await get_todo_list(done, transaction)
 4
 5
 6@post("/")
 7async def add_item(data: TodoItem, transaction: AsyncSession) -> TodoItem:
 8    transaction.add(data)
 9    return data
10
11
12@put("/{item_title:str}")
13async def update_item(item_title: str, data: TodoItem, transaction: AsyncSession) -> TodoItem:
14    todo_item = await get_todo_by_title(item_title, transaction)
15    todo_item.title = data.title
16    todo_item.done = data.done

Finally, we define our application, using the SQLAlchemyPlugin to configure SQLAlchemy and manage the engine and session lifecycle, and register our transaction dependency.

1    create_all=True,
2    before_send_handler=autocommit_before_send_handler,
3)
4
5app = Litestar(

See also