先下结论

先说结论, 一般来说, 在项目初始就定好规矩, 在restful中, 将所有资源都看成文件, 那么统一成不加/的好, 然后访问加了斜杠的路径会报404, 加不加看心情但是一个项目中最好统一.

因为在flask中如果路由是/haha/, 那么访问/haha会被重定向到/haha/下

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qq@zz:~/test$ curl -I  http://127.0.0.1:3000/users/kaka
HTTP/1.0 308 PERMANENT REDIRECT
Content-Type: text/html; charset=utf-8
Content-Length: 273
Location: http://127.0.0.1:3000/users/kaka/
Server: Werkzeug/0.15.4 Python/3.6.6
Date: Mon, 20 May 2019 07:39:15 GMT

但是定义一个/haha的路径, 然后访问/haha/会报404:

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qq@zz:~/test$ curl -I  http://127.0.0.1:3000/users/kaka/
HTTP/1.0 404 NOT FOUND
Content-Type: text/html
Content-Length: 232
Server: Werkzeug/0.15.4 Python/3.6.6
Date: Mon, 20 May 2019 07:53:04 GMT

举例子

在flask路由的时候发现一个很好玩的事情, 代码如下:

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from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/users/kaka')
def update_user():
    return jsonify(a=1)

@app.route('/users/kaka/')
def update_userss():
    return jsonify(a=11)

if __name__ == '__main__':
    app.run(debug=True, port=3000)

然后调用:

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qq@zz:~$ curl http://127.0.0.1:3000/users/kaka/
{
  "a": 11
}
qq@zz:~$ curl http://127.0.0.1:3000/users/kaka
{
  "a": 1
}
# 这是因为werkzug中所有的路由都存在一个列表中, 所以涉及到匹配的先后顺序

然后将路径/users/kaka最后的斜杠顺序换过来:

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from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/users/kaka/')
def update_user():
    return jsonify(a=1)

@app.route('/users/kaka')
def update_userss():
    return jsonify(a=11)

if __name__ == '__main__':
    app.run(debug=True, port=3000)

返回结果:

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qq@zz:~$ curl http://127.0.0.1:3000/users/kaka/
{
  "a": 1
}
qq@zz:~$ curl http://127.0.0.1:3000/users/kaka
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<title>Redirecting...</title>
<h1>Redirecting...</h1>
<p>You should be redirected automatically to target URL: <a href="http://127.0.0.1:3000/users/kaka/">http://127.0.0.1:3000/users/kaka/</a>.  If not click the link.

找解决

在werkzeug/routing.py中:

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    - you receive a `RequestRedirect` exception with a `new_url`
      attribute.  This exception is used to notify you about a request
      Werkzeug requests from your WSGI application.  This is for example the
      case if you request ``/foo`` although the correct URL is ``/foo/``
      You can use the `RequestRedirect` instance as response-like object
      similar to all other subclasses of `HTTPException`.

`string`
    Rule strings basically are just normal URL paths with placeholders in
    the format ``<converter(arguments):name>`` where the converter and the
    arguments are optional.  If no converter is defined the `default`
    converter is used which means `string` in the normal configuration.

    URL rules that end with a slash are branch URLs, others are leaves.
    If you have `strict_slashes` enabled (which is the default), all
    branch URLs that are matched without a trailing slash will trigger a
    redirect to the same URL with the missing slash appended.

追溯到第一使用地点:

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class Rule:

    def match(self, **kwargs):
        if (
            self.strict_slashes
            and not self.is_leaf
            and not groups.pop("__suffix__")
            and (
                method is None or self.methods is None or method in self.methods
                )
            ):
                raise RequestSlash()


class MapAdapter(object):
    def match(self, path_info=None, method=None, return_rule=False, query_args=None):
        for rule in self.map._rules:
        try:
            rv = rule.match(path, method)
        except RequestSlash:
            raise RequestRedirect(
                self.make_redirect_url(
                    url_quote(path_info, self.map.charset, safe="/:|+") +"/",
                    query_args,
                )
            )
        except RequestAliasRedirect as e:
            raise RequestRedirect(
                self.make_alias_redirect_url(
                        path, rule.endpoint, e.matched_values, method, query_args
                )
            )

class Map:

    def __init__(strict_slashes=True,
                redirect_defaults=True,):
        pass

小总结

最后为什么一个匹配的上一个匹配不上, 这涉及到werkzeug的路由建立顺序和匹配顺序, 在另一篇路由的实现和查找中有提到.

番外–linux的普通文件和目录文件

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qq@zz:~/test$ touch haha
qq@zz:~/test$ mkdir kaka
qq@zz:~/test$ stat haha
  文件：'haha'
  大小：0         	块：0          IO 块：4096   普通空文件
设备：806h/2054d	Inode：1058541     硬链接：1
权限：(0664/-rw-rw-r--)  Uid：( 1000/      qq)   Gid：( 1000/      qq)
最近访问：2019-05-20 15:34:08.849485139 +0800
最近更改：2019-05-20 15:34:08.849485139 +0800
最近改动：2019-05-20 15:34:08.849485139 +0800
创建时间：-
qq@zz:~/test$ stat kaka
  文件：'kaka'
  大小：4096      	块：8          IO 块：4096   目录
设备：806h/2054d	Inode：1061448     硬链接：2
权限：(0775/drwxrwxr-x)  Uid：( 1000/      qq)   Gid：( 1000/      qq)
最近访问：2019-05-20 15:34:12.837483383 +0800
最近更改：2019-05-20 15:34:12.837483383 +0800
最近改动：2019-05-20 15:34:12.837483383 +0800
创建时间：-
qq@zz:~/test$ ll
总用量 12
drwxrwxr-x  3 qq qq 4096 5月  20 15:34 ./
drwxr-xr-x 80 qq qq 4096 5月  20 15:02 ../
-rw-rw-r--  1 qq qq    0 5月  20 15:34 haha
drwxrwxr-x  2 qq qq 4096 5月  20 15:34 kaka/

在linux下面, 普通文件结尾为filename, 目录文件结尾是dirname/