tut2

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Presenter: James Huang
Date: Sept. 29, 2014
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HTTP and WWW
Bottle Web Framework
Request Routing
Sending Static Files
Handling HTML <Form>
HTTP Errors and Redirects
Cookies
Templates
Plugins
Demo
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World Wide Web (WWW) uses Hypertext Transfer
Protocol (HTTP) as a standard for web client and
web server to communicate.
HTTP uses a request-response computing model.
◦ A server listens for clients’ connection over TCP.
◦ A client (e.g. web browser) sends a request message to
server.
◦ The server sends back a status line followed by a
response message.
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HTTP is a stateless protocol.
◦ Web applications often use cookies to maintain states.
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An HTTP client specifies request methods to
distinguish different types of actions to be
performed on the server.
GET
◦ Retrieves data from the server
◦ Should not have other effect on the server
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POST
◦ Requests that the server accepts the data enclosed
in the request
◦ Used to submit a form, upload a file, etc.
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An HTTP session is a sequence of requestresponse transactions.
Web Client
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GET /index.html HTTP/1.1
Host: www.example.com
2.
HTTP/1.0 200 OK
Date: Mon, 29 Sep 2014 03:50:21 GMT
Server: WSGIServer/0.1 Python/2.7.2
Content-Length: 32
Content-Type: text/html; charset=UTF-8
Web Server
<html>
<body>
Hello World.
</body>
</html>
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Bottle is a web server that allows developers
to write web applications in Python.
It is easy to install and use.
◦ Implemented in Python
◦ Has no dependency on any external libraries
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Writing web application for Bottle is simple.
◦ A web application consists of callback functions
that are called by Bottle to handle HTTP requests.
◦ Bottle handles errors and exceptions automatically.
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hello.py:
# A simple web application
Imports Bottle web framework
from bottle import run, route
Links ‘/’ to home()
@route('/')
def home():
return '<html><body>Hello World.</body></html>‘
run(host='localhost', port=8080, debug=True)
Starts web server on port 8080
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URLs are linked to callback functions with route()
decorator.
URL contains wildcards, dynamic route, can be
used to match more than one URL.
@route(‘/hello/<name>’)
def hello(name):
return greet(name)
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More than one route can be used for a single
callback function.
@route(‘/’)
@route(‘/hello/<name>’)
def hello(name=‘Stranger’):
return greet(name)
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A simple wildcard (e.g. <name>) matches one or
more characters up to the next slash (‘/’).
◦ E.g. ‘/hello/<name>’ matches ‘/hello/bob’, but not
‘/hello’ or ‘/hello/john/smith’.
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Each wildcard passes the matched part of URL as
a keyword argument to the callback function.
Filters can be used to match specific wildcards
and converts matched part of URL.
◦ :int – matches digits only and converts the value to
integer
◦ :path – matches more than one path segment
◦ :re – matches with a regular expression
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A web application needs to have a callback to
handle which files to serve to a client.
◦ Bottle does not automatically serve files to client.
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Bottle provides static_file() helper function.
match URL with
from bottle import static_file
@route('/images/<filename:re:.*\.png>') regular expression
def send_image(filename):
return static_file(filename,
root='/path/to/image/files', mimetype='image/png')
match URL with path
@route('/html/<filepath:path>')
def server_static(filepath):
return static_file(filepath,
root='/path/to/your/html/files')
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HTML usually specify to use POST request
method to send form data.
Bottle’s route decorator applies to GET request
method by default.
A web application can specify request method as
an argument of route decorator.
◦ E.g. @route(‘/login’, method=‘POST’)
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Bottle also provides different decorators to
handle different request methods: @get, @post,
etc. as shortcuts.
The value of an Input field of a form can be
retrieved with request object.
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from bottle import get, post, request # or route
@get('/login') # or @route('/login') login() is called when user browse
to /login
def login():
return ''' <form action="/login" method="post"> Username: <input
name="username" type="text" /> Password: <input name="password"
type="password" /> <input value="Login" type="submit" /> </form>
'''
@post('/login') # or @route('/login', method='POST')
def do_login():
do_login() is called when user
username = request.forms.get('username')
submit the form
password = request.forms.get('password')
if check_login(username, password):
request
is used to retrieve
return "<p>Your login information
wasobject
correct.</p>"
the value of an input field
else:
return "<p>Login failed.</p>"
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The abort() function is used to generate an
HTTP error page.
from bottle import route, abort
@route('/restricted')
def restricted():
abort(401, "Sorry, access denied.")
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The redirect() function redirects a client to a
different URL.
from bottle import redirect
@route('/wrong/url')
def wrong():
redirect("/right/url")
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A cookie stores site-specific text information
in a web browser’s profile.
A web application creates a new cookie with
Response.set_cookie(), access a cookie with
Request.get_cookie().
@route('/hello')
def hello_again():
if request.get_cookie("visited"):
return "Welcome back! Nice to see you again"
else:
response.set_cookie("visited", "yes")
return "Hello there! Nice to meet you"
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A cookie can be controlled with different
settings.
◦ max_age: maximum age in seconds
◦ expires: the timestamp when the cookie expires
◦ secure: limit the cookie to HTTPS connections
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These settings can be specified as keyword
arguments to Response.set_cookie().
Cookie expires at the end of a browser
session, unless max_age or expires is set.
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Bottle provide a convenient way to generate
web page from templates.
Here is an example template:
%if name == 'World':
<h1>Hello {{name}}!</h1>
<p>This is a test.</p>
%else:
<h1>Hello {{name.title()}}!</h1>
<p>How are you?</p>
%end
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Python-like syntax
A web application uses templates with
template() function.
@route('/hello/<name>')
def hello(name):
return template('hello_template',
name=name)
hello_template.tpl
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Bottle supports third-party plugins:
◦ Bottle-Sqlite: SQLite3 database plugin
◦ Bottle-Redis: Redis database plugin
◦ Bottle-Flash: flash plugin
from bottle import route, install, template
from bottle_sqlite import SQLitePlugin
install(SQLitePlugin(dbfile='/tmp/test.db'))
@route('/show/<post_id:int>')
def show(db, post_id):
SQLitePlugin detects
the use of db and
creates a new
database
connection.
c = db.execute('SELECT title, content FROM posts WHERE id = ?',
(post_id,))
row = c.fetchone()
return template('show_post', title=row['title'], text=row['content'])
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Thank you!
contact: [email protected]
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