a4185a0ba7
* blueprints * class_based_views * config * decorators * deploying * exceptions * extensions * getting_started * middleware * request_data * response * routing * static_files * streaming * testing * versioning * Fix bug and links * spelling mistakes * Bug fixes and minor tweaks * Create 1691.doc.rst * Bug fixes and tweaks Co-Authored-By: Harsha Narayana <harsha2k4@gmail.com>
302 lines
8.2 KiB
ReStructuredText
302 lines
8.2 KiB
ReStructuredText
Blueprints
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==========
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Blueprints are objects that can be used for sub-routing within an application.
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Instead of adding routes to the application instance, blueprints define similar
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methods for adding routes, which are then registered with the application in a
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flexible and pluggable manner.
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Blueprints are especially useful for larger applications, where your
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application logic can be broken down into several groups or areas of
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responsibility.
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My First Blueprint
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------------------
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The following shows a very simple blueprint that registers a handler-function at
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the root `/` of your application.
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Suppose you save this file as `my_blueprint.py`, which can be imported into your
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main application later.
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.. code-block:: python
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from sanic.response import json
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from sanic import Blueprint
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bp = Blueprint('my_blueprint')
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@bp.route('/')
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async def bp_root(request):
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return json({'my': 'blueprint'})
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Registering blueprints
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----------------------
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Blueprints must be registered with the application.
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.. code-block:: python
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from sanic import Sanic
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from my_blueprint import bp
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app = Sanic(__name__)
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app.blueprint(bp)
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app.run(host='0.0.0.0', port=8000, debug=True)
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This will add the blueprint to the application and register any routes defined
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by that blueprint. In this example, the registered routes in the `app.router`
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will look like:
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.. code-block:: python
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[Route(handler=<function bp_root at 0x7f908382f9d8>, methods=frozenset({'GET'}), pattern=re.compile('^/$'), parameters=[], name='my_blueprint.bp_root', uri='/')]
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Blueprint groups and nesting
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----------------------------
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Blueprints may also be registered as part of a list or tuple, where the registrar will recursively cycle through any sub-sequences of blueprints and register them accordingly. The `Blueprint.group` method is provided to simplify this process, allowing a 'mock' backend directory structure mimicking what's seen from the front end. Consider this (quite contrived) example:
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| api/
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| ├──content/
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| │ ├──authors.py
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| │ ├──static.py
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| │ └──__init__.py
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| ├──info.py
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| └──__init__.py
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| app.py
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Initialization of this app's blueprint hierarchy could go as follows:
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.. code-block:: python
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# api/content/authors.py
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from sanic import Blueprint
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authors = Blueprint('content_authors', url_prefix='/authors')
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.. code-block:: python
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# api/content/static.py
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from sanic import Blueprint
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static = Blueprint('content_static', url_prefix='/static')
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.. code-block:: python
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# api/content/__init__.py
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from sanic import Blueprint
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from .static import static
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from .authors import authors
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content = Blueprint.group(static, authors, url_prefix='/content')
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.. code-block:: python
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# api/info.py
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from sanic import Blueprint
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info = Blueprint('info', url_prefix='/info')
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.. code-block:: python
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# api/__init__.py
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from sanic import Blueprint
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from .content import content
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from .info import info
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api = Blueprint.group(content, info, url_prefix='/api')
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And registering these blueprints in `app.py` can now be done like so:
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.. code-block:: python
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# app.py
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from sanic import Sanic
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from .api import api
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app = Sanic(__name__)
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app.blueprint(api)
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Using Blueprints
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----------------
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Blueprints have almost the same functionality as an application instance.
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WebSocket routes
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~~~~~~~~~~~~~~~~
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WebSocket handlers can be registered on a blueprint using the `@bp.websocket`
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decorator or `bp.add_websocket_route` method.
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Blueprint Middleware
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~~~~~~~~~~~~~~~~~~~~
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Using blueprints allows you to also register middleware globally.
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.. code-block:: python
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@bp.middleware
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async def print_on_request(request):
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print("I am a spy")
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@bp.middleware('request')
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async def halt_request(request):
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return text('I halted the request')
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@bp.middleware('response')
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async def halt_response(request, response):
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return text('I halted the response')
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Blueprint Group Middleware
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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Using this middleware will ensure that you can apply a common middleware to all the blueprints that form the
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current blueprint group under consideration.
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.. code-block:: python
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bp1 = Blueprint('bp1', url_prefix='/bp1')
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bp2 = Blueprint('bp2', url_prefix='/bp2')
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@bp1.middleware('request')
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async def bp1_only_middleware(request):
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print('applied on Blueprint : bp1 Only')
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@bp1.route('/')
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async def bp1_route(request):
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return text('bp1')
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@bp2.route('/<param>')
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async def bp2_route(request, param):
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return text(param)
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group = Blueprint.group(bp1, bp2)
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@group.middleware('request')
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async def group_middleware(request):
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print('common middleware applied for both bp1 and bp2')
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# Register Blueprint group under the app
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app.blueprint(group)
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Exceptions
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~~~~~~~~~~
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Exceptions can be applied exclusively to blueprints globally.
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.. code-block:: python
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@bp.exception(NotFound)
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def ignore_404s(request, exception):
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return text("Yep, I totally found the page: {}".format(request.url))
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Static files
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~~~~~~~~~~~~
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Static files can be served globally, under the blueprint prefix.
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.. code-block:: python
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# suppose bp.name == 'bp'
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bp.static('/web/path', '/folder/to/serve')
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# also you can pass name parameter to it for url_for
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bp.static('/web/path', '/folder/to/server', name='uploads')
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app.url_for('static', name='bp.uploads', filename='file.txt') == '/bp/web/path/file.txt'
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Start and stop
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--------------
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Blueprints can run functions during the start and stop process of the server.
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If running in multiprocessor mode (more than 1 worker), these are triggered
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after the workers fork.
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Available events are:
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- `before_server_start`: Executed before the server begins to accept connections
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- `after_server_start`: Executed after the server begins to accept connections
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- `before_server_stop`: Executed before the server stops accepting connections
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- `after_server_stop`: Executed after the server is stopped and all requests are complete
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.. code-block:: python
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bp = Blueprint('my_blueprint')
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@bp.listener('before_server_start')
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async def setup_connection(app, loop):
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global database
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database = mysql.connect(host='127.0.0.1'...)
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@bp.listener('after_server_stop')
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async def close_connection(app, loop):
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await database.close()
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Use-case: API versioning
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------------------------
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Blueprints can be very useful for API versioning, where one blueprint may point
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at `/v1/<routes>`, and another pointing at `/v2/<routes>`.
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When a blueprint is initialised, it can take an optional `version` argument,
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which will be prepended to all routes defined on the blueprint. This feature
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can be used to implement our API versioning scheme.
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.. code-block:: python
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# blueprints.py
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from sanic.response import text
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from sanic import Blueprint
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blueprint_v1 = Blueprint('v1', url_prefix='/api', version="v1")
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blueprint_v2 = Blueprint('v2', url_prefix='/api', version="v2")
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@blueprint_v1.route('/')
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async def api_v1_root(request):
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return text('Welcome to version 1 of our documentation')
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@blueprint_v2.route('/')
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async def api_v2_root(request):
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return text('Welcome to version 2 of our documentation')
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When we register our blueprints on the app, the routes `/v1/api` and `/v2/api` will now
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point to the individual blueprints, which allows the creation of *sub-sites*
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for each API version.
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.. code-block:: python
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# main.py
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from sanic import Sanic
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from blueprints import blueprint_v1, blueprint_v2
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app = Sanic(__name__)
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app.blueprint(blueprint_v1)
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app.blueprint(blueprint_v2)
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app.run(host='0.0.0.0', port=8000, debug=True)
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URL Building with `url_for`
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---------------------------
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If you wish to generate a URL for a route inside of a blueprint, remember that the endpoint name
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takes the format `<blueprint_name>.<handler_name>`. For example:
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.. code-block:: python
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@blueprint_v1.route('/')
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async def root(request):
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url = request.app.url_for('v1.post_handler', post_id=5) # --> '/v1/api/post/5'
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return redirect(url)
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@blueprint_v1.route('/post/<post_id>')
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async def post_handler(request, post_id):
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return text('Post {} in Blueprint V1'.format(post_id))
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