218 lines
6.9 KiB
Markdown
218 lines
6.9 KiB
Markdown
# Routing
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Routing allows the user to specify handler functions for different URL endpoints.
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A basic route looks like the following, where `app` is an instance of the
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`Sanic` class:
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```python
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from sanic.response import json
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@app.route("/")
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async def test(request):
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return json({ "hello": "world" })
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```
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When the url `http://server.url/` is accessed (the base url of the server), the
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final `/` is matched by the router to the handler function, `test`, which then
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returns a JSON object.
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Sanic handler functions must be defined using the `async def` syntax, as they
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are asynchronous functions.
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## Request parameters
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Sanic comes with a basic router that supports request parameters.
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To specify a parameter, surround it with angle quotes like so: `<PARAM>`.
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Request parameters will be passed to the route handler functions as keyword
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arguments.
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```python
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from sanic.response import text
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@app.route('/tag/<tag>')
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async def tag_handler(request, tag):
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return text('Tag - {}'.format(tag))
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```
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To specify a type for the parameter, add a `:type` after the parameter name,
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inside the quotes. If the parameter does not match the specified type, Sanic
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will throw a `NotFound` exception, resulting in a `404: Page not found` error
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on the URL.
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```python
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from sanic.response import text
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@app.route('/number/<integer_arg:int>')
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async def integer_handler(request, integer_arg):
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return text('Integer - {}'.format(integer_arg))
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@app.route('/number/<number_arg:number>')
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async def number_handler(request, number_arg):
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return text('Number - {}'.format(number_arg))
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@app.route('/person/<name:[A-z]>')
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async def person_handler(request, name):
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return text('Person - {}'.format(name))
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@app.route('/folder/<folder_id:[A-z0-9]{0,4}>')
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async def folder_handler(request, folder_id):
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return text('Folder - {}'.format(folder_id))
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```
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## HTTP request types
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By default, a route defined on a URL will be available for only GET requests to that URL.
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However, the `@app.route` decorator accepts an optional parameter, `methods`,
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which allows the handler function to work with any of the HTTP methods in the list.
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```python
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from sanic.response import text
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@app.route('/post', methods=['POST'])
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async def post_handler(request):
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return text('POST request - {}'.format(request.json))
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@app.route('/get', methods=['GET'])
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async def get_handler(request):
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return text('GET request - {}'.format(request.args))
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```
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There is also an optional `host` argument (which can be a list or a string). This restricts a route to the host or hosts provided. If there is a also a route with no host, it will be the default.
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```python
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@app.route('/get', methods=['GET'], host='example.com')
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async def get_handler(request):
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return text('GET request - {}'.format(request.args))
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# if the host header doesn't match example.com, this route will be used
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@app.route('/get', methods=['GET'])
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async def get_handler(request):
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return text('GET request in default - {}'.format(request.args))
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```
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There are also shorthand method decorators:
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```python
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from sanic.response import text
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@app.post('/post')
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async def post_handler(request):
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return text('POST request - {}'.format(request.json))
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@app.get('/get')
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async def get_handler(request):
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return text('GET request - {}'.format(request.args))
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```
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## The `add_route` method
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As we have seen, routes are often specified using the `@app.route` decorator.
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However, this decorator is really just a wrapper for the `app.add_route`
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method, which is used as follows:
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```python
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from sanic.response import text
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# Define the handler functions
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async def handler1(request):
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return text('OK')
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async def handler2(request, name):
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return text('Folder - {}'.format(name))
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async def person_handler2(request, name):
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return text('Person - {}'.format(name))
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# Add each handler function as a route
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app.add_route(handler1, '/test')
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app.add_route(handler2, '/folder/<name>')
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app.add_route(person_handler2, '/person/<name:[A-z]>', methods=['GET'])
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```
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## URL building with `url_for`
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Sanic provides a `url_for` method, to generate URLs based on the handler method name. This is useful if you want to avoid hardcoding url paths into your app; instead, you can just reference the handler name. For example:
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```python
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@app.route('/')
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async def index(request):
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# generate a URL for the endpoint `post_handler`
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url = app.url_for('post_handler', post_id=5)
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# the URL is `/posts/5`, redirect to it
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return redirect(url)
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@app.route('/posts/<post_id>')
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async def post_handler(request, post_id):
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return text('Post - {}'.format(post_id))
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```
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Other things to keep in mind when using `url_for`:
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- Keyword arguments passed to `url_for` that are not request parameters will be included in the URL's query string. For example:
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```python
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url = app.url_for('post_handler', post_id=5, arg_one='one', arg_two='two')
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# /posts/5?arg_one=one&arg_two=two
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```
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- Multivalue argument can be passed to `url_for`. For example:
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```python
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url = app.url_for('post_handler', post_id=5, arg_one=['one', 'two'])
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# /posts/5?arg_one=one&arg_one=two
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```
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- Also some special arguments (`_anchor`, `_external`, `_scheme`, `_method`, `_server`) passed to `url_for` will have special url building (`_method` is not support now and will be ignored). For example:
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```python
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url = app.url_for('post_handler', post_id=5, arg_one='one', _anchor='anchor')
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# /posts/5?arg_one=one#anchor
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url = app.url_for('post_handler', post_id=5, arg_one='one', _external=True)
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# //server/posts/5?arg_one=one
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# _external requires passed argument _server or SERVER_NAME in app.config or url will be same as no _external
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url = app.url_for('post_handler', post_id=5, arg_one='one', _scheme='http', _external=True)
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# http://server/posts/5?arg_one=one
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# when specifying _scheme, _external must be True
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# you can pass all special arguments one time
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url = app.url_for('post_handler', post_id=5, arg_one=['one', 'two'], arg_two=2, _anchor='anchor', _scheme='http', _external=True, _server='another_server:8888')
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# http://another_server:8888/posts/5?arg_one=one&arg_one=two&arg_two=2#anchor
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```
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- All valid parameters must be passed to `url_for` to build a URL. If a parameter is not supplied, or if a parameter does not match the specified type, a `URLBuildError` will be thrown.
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## WebSocket routes
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Routes for the WebSocket protocol can be defined with the `@app.websocket`
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decorator:
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```python
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@app.websocket('/feed')
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async def feed(request, ws):
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while True:
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data = 'hello!'
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print('Sending: ' + data)
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await ws.send(data)
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data = await ws.recv()
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print('Received: ' + data)
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```
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Alternatively, the `app.add_websocket_route` method can be used instead of the
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decorator:
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```python
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async def feed(request, ws):
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pass
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app.add_websocket_route(my_websocket_handler, '/feed')
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```
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Handlers for a WebSocket route are passed the request as first argument, and a
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WebSocket protocol object as second argument. The protocol object has `send`
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and `recv` methods to send and receive data respectively.
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WebSocket support requires the [websockets](https://github.com/aaugustin/websockets)
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package by Aymeric Augustin.
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