Flask快速入门(17) — flask_session

Flask快速入门(17) — flask_session

作用：将默认保存的签名cookie中的值，保存到 redis/memcached/file/Mongodb/SQLAlchemy

安装：pip install flask-session

使用1：

from flask import Flask,session
from flask_session import RedisSessionInterface
import redis
app = Flask(__name__)
conn=redis.Redis(host='127.0.0.1',port=6379)  # 连接redis

# use_signer是否对key签名
# 如果use_siginer为False,这表示不需要配置app.secret_key
app.session_interface=RedisSessionInterface(conn,key_prefix='lqz')
@app.route('/')
def hello_world():
    session['name']='lqz'
    return 'Hello World!'

if __name__ == '__main__':
    app.run()

我们知道session是从app.session_interface入口。所以要改变存储位置的话，要重写app.session_interface。在这里的RedisSessionInterface重写了open_session（取）和save_session(存)。我们来看看RedisSessionInterface这个类

class RedisSessionInterface(SessionInterface):
    serializer = pickle
    session_class = RedisSession
    # 实例化参数：redis连接的redis; key_prefix存储的前缀; user_signer是否对key签名，为False则不需要设置secret_key,为True时，需要设置; permanent关闭浏览器是否保存，为Frue保存，为False不保存
    def __init__(self, redis, key_prefix, use_signer=False, permanent=True):
        if redis is None:
            from redis import Redis
            redis = Redis()
        self.redis = redis
        self.key_prefix = key_prefix
        self.use_signer = use_signer
        self.permanent = permanent
        
    def open_session(self, app, request):
        sid = request.cookies.get(app.session_cookie_name)
        if not sid:
            sid = self._generate_sid()
            return self.session_class(sid=sid, permanent=self.permanent)
        if self.use_signer:
            signer = self._get_signer(app)
            if signer is None:
                return None
            try:
                sid_as_bytes = signer.unsign(sid)
                sid = sid_as_bytes.decode()
            except BadSignature:
                sid = self._generate_sid()
                return self.session_class(sid=sid, permanent=self.permanent)

        if not PY2 and not isinstance(sid, text_type):
            sid = sid.decode('utf-8', 'strict')
        val = self.redis.get(self.key_prefix + sid)  # 从redis中取出session
        if val is not None:
            try:
                data = self.serializer.loads(val)  # 获取session反序列化值
                return self.session_class(data, sid=sid)
            except:
                return self.session_class(sid=sid, permanent=self.permanent)
        return self.session_class(sid=sid, permanent=self.permanent)

    def save_session(self, app, session, response):
        domain = self.get_cookie_domain(app)
        path = self.get_cookie_path(app)
        if not session:
            if session.modified:
                self.redis.delete(self.key_prefix + session.sid)
                response.delete_cookie(app.session_cookie_name,
                                       domain=domain, path=path)
            return
        httponly = self.get_cookie_httponly(app)
        secure = self.get_cookie_secure(app)
        expires = self.get_expiration_time(app, session)
        val = self.serializer.dumps(dict(session))  # 将session序列化放入val中
        # 将session设置到redis,name=前缀+字符串，value=session值
        self.redis.setex(name=self.key_prefix + session.sid, value=val,
                         time=total_seconds(app.permanent_session_lifetime))
        if self.use_signer:
            session_id = self._get_signer(app).sign(want_bytes(session.sid))
        else:
            session_id = session.sid
        response.set_cookie(app.session_cookie_name, session_id,
                            expires=expires, httponly=httponly,
                            domain=domain, path=path, secure=secure)

使用2：

from flask import Flask,session
from redis import Redis
from flask_session import Session
app = Flask(__name__)
app.config['SESSION_TYPE'] = 'redis'
app.config['SESSION_REDIS'] = Redis(host='127.0.0.1',port='6379')
Session(app)

@app.route('/')
def index():
    session['name'] = 'nick'
    return 'hello'

@app.route('/index')
def test():
    return session['name']

if __name__ == '__main__':
    app.run()

主要是通过配置SESSION_TYPE源码中进行相应的存储：Session(app)源码

def __init__(self, app=None):
    self.app = app
    if app is not None:
        self.init_app(app)

self.init_app(app)源码：

def init_app(self, app):
    app.session_interface = self._get_interface(app)  # 在这里重写了session_interface

self._get_interface(app)源码：

def _get_interface(self, app):
    # 在这里做了一些相关的配置
    config = app.config.copy()
    config.setdefault('SESSION_TYPE', 'null')
    config.setdefault('SESSION_PERMANENT', True)
    config.setdefault('SESSION_USE_SIGNER', False)
    config.setdefault('SESSION_KEY_PREFIX', 'session:')
    config.setdefault('SESSION_REDIS', None)
    config.setdefault('SESSION_MEMCACHED', None)
    config.setdefault('SESSION_FILE_DIR',
                      os.path.join(os.getcwd(), 'flask_session'))
    config.setdefault('SESSION_FILE_THRESHOLD', 500)
    config.setdefault('SESSION_FILE_MODE', 384)
    config.setdefault('SESSION_MONGODB', None)
    config.setdefault('SESSION_MONGODB_DB', 'flask_session')
    config.setdefault('SESSION_MONGODB_COLLECT', 'sessions')
    config.setdefault('SESSION_SQLALCHEMY', None)
    config.setdefault('SESSION_SQLALCHEMY_TABLE', 'sessions')
	
    # 通过if...elif...else来判断匹配config['SESSION_TYPE']，再执行相应的session_interface
    if config['SESSION_TYPE'] == 'redis':
        session_interface = RedisSessionInterface(
            config['SESSION_REDIS'], config['SESSION_KEY_PREFIX'],
            config['SESSION_USE_SIGNER'], config['SESSION_PERMANENT'])
    elif config['SESSION_TYPE'] == 'memcached':
        session_interface = MemcachedSessionInterface(
            config['SESSION_MEMCACHED'], config['SESSION_KEY_PREFIX'],
            config['SESSION_USE_SIGNER'], config['SESSION_PERMANENT'])
    elif config['SESSION_TYPE'] == 'filesystem':
        session_interface = FileSystemSessionInterface(
            config['SESSION_FILE_DIR'], config['SESSION_FILE_THRESHOLD'],
            config['SESSION_FILE_MODE'], config['SESSION_KEY_PREFIX'],
            config['SESSION_USE_SIGNER'], config['SESSION_PERMANENT'])
    elif config['SESSION_TYPE'] == 'mongodb':
        session_interface = MongoDBSessionInterface(
            config['SESSION_MONGODB'], config['SESSION_MONGODB_DB'],
            config['SESSION_MONGODB_COLLECT'],
            config['SESSION_KEY_PREFIX'], config['SESSION_USE_SIGNER'],
            config['SESSION_PERMANENT'])
    elif config['SESSION_TYPE'] == 'sqlalchemy':
        session_interface = SqlAlchemySessionInterface(
            app, config['SESSION_SQLALCHEMY'],
            config['SESSION_SQLALCHEMY_TABLE'],
            config['SESSION_KEY_PREFIX'], config['SESSION_USE_SIGNER'],
            config['SESSION_PERMANENT'])
    else:
        session_interface = NullSessionInterface()
    return session_interface

问题：设置cookie时，如何设定关闭浏览器则cookie失效。

response.set_cookie('k','v',exipre=None)#这样设置即可
#在session中设置
app.session_interface=RedisSessionInterface(conn,key_prefix='lqz',permanent=False)
#一般不用，我们一般都设置超时时间，多长时间后失效

问题：cookie默认超时时间是多少？如何设置超时时间

#源码expires = self.get_expiration_time(app, session)
'PERMANENT_SESSION_LIFETIME':           timedelta(days=31),#这个配置文件控制