83 lines
2.1 KiB
Markdown
83 lines
2.1 KiB
Markdown
# Blueprints
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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 object, 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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## Why?
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Blueprints are especially useful for larger applications, where your application
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logic can be broken down into several groups or areas of responsibility.
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It is also useful for API versioning, where one blueprint may point at
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`/v1/<routes>`, and another pointing at `/v2/<routes>`.
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## My First Blueprint
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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`, this can be imported in your
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main application later.
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```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():
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return json({'my': 'blueprint'})
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```
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## Registering Blueprints
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Blueprints must be registered with the application.
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```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.register_blueprint(bp)
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app.run(host='0.0.0.0', port=8000, debug=True)
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```
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This will add the blueprint to the application and register any routes defined
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by that blueprint.
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In this example, the registered routes in the `app.router` will look like:
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```python
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[Route(handler=<function bp_root at 0x7f908382f9d8>, methods=None, pattern=re.compile('^/$'), parameters=[])]
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```
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## Middleware
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Using blueprints allows you to also register middleware globally.
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```python
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@bp.middleware
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async def halt_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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```
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## Exceptions
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Exceptions can also be applied exclusively to blueprints globally.
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```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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```
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