Laravel学习笔记之Session源码解析(上)

说明:本文主要通过学习Laravel的session源码学习Laravel是如何设计session的,将自己的学习心得分享出来,希望对别人有所帮助。Laravel在web middleware中定义了session中间件\Illuminate\Session\Middleware\StartSession::class,并通过该中间件来设计session,这个中间件的主要工作分为三步:(1)启动session,通过session handler从一些存储介质如redis中读取session值;(2)操作session,对session数据CRUD增删改查操作;(3)关闭session,把session_id写入到response header中,默认是laravel_session

开发环境:Laravel5.3 PHP7

启动Session

首先看下\Illuminate\Session\Middleware\StartSession::class中间件源码中handle()方法:

    public function handle($request, Closure $next)
    {
        // 前置操作
        $this->sessionHandled = true;

        if ($this->sessionConfigured()) {
            // Start session.
            /**
             * @var \Illuminate\Session\Store $session
             */
            $session = $this->startSession($request);

            $request->setSession($session);

            $this->collectGarbage($session);
        }

        $response = $next($request);

        // 后置操作
        if ($this->sessionConfigured()) {
            $this->storeCurrentUrl($request, $session);

            $this->addCookieToResponse($response, $session);
        }

        return $response;
    }

Laravel学习笔记之Middleware源码解析这篇文章中知道,该中间件有前置操作和后置操作。看下sessionConfigured()的源码:

    /**
     * Determine if a session driver has been configured.
     *
     * @return bool
     */
    protected function sessionConfigured()
    {
        // 检查session.php中driver选项是否设置
        return ! is_null(Arr::get($this->manager->getSessionConfig(), \'driver\'));
    }
    
    // \Illuminate\Session\SessionManager
    /**
     * Get the session configuration.
     *
     * @return array
     */
    public function getSessionConfig()
    {
        return $this->app[\'config\'][\'session\'];
    }

首先中间件检查session.php中driver选项是否设置,这里假设设置为经常使用的redis作为session的存储介质,并且需要在database.php中设置下redis的链接,本地需要装好redis,通过redis-cli命令查看redis是否已经安装好。OK,然后中间件使用startSession()方法来启动session:

    protected function startSession(Request $request)
    {
        /**
         * @var \Illuminate\Session\Store $session
         */
        $session = $this->getSession($request); // 获取session实例,Laravel使用Store类来管理session

        $session->setRequestOnHandler($request);

        // Load the session data from the store repository by the handler.
        $session->start();

        return $session;
    }
    
    public function getSession(Request $request)
    {
        /**
         * Get the session store instance via the driver.
         *
         * @var \Illuminate\Session\Store $session
         */
        $session = $this->manager->driver();

        /**
         * $session->getName() === \'laravel_session\' === config(\'session.cookie\')
         */
        $session->setId($request->cookies->get($session->getName()));

        return $session;
    }

startSession()主要分为两步:获取session实例\Illuminate\Session\Store,主要步骤是$session = $this->manager->driver();通过该实例从存储介质中读取该次请求所需要的session数据,主要步骤是$session->start()。首先看下第一步的源码:

    // \Illuminate\Support\Manager
    public function driver($driver = null)
    {
        // $driver = \'redis\'
        $driver = $driver ?: $this->getDefaultDriver();
       
        if (! isset($this->drivers[$driver])) {
            $this->drivers[$driver] = $this->createDriver($driver);
        }

        return $this->drivers[$driver];
    }
    
    protected function createDriver($driver)
    {
        $method = \'create\'.Str::studly($driver).\'Driver\';

        if (isset($this->customCreators[$driver])) {
            return $this->callCustomCreator($driver);
        } elseif (method_exists($this, $method)) { // 判断\Illuminate\Session\SessionManager中是否存在createRedisDriver()方法
            // 存在,call这个createRedisDriver()方法
            return $this->$method();
        }

        throw new InvalidArgumentException("Driver [$driver] not supported.");
    }
    
    // \Illuminate\Session\SessionManager
    public function getDefaultDriver()
    {
        // 返回 \'redis\'
        return $this->app[\'config\'][\'session.driver\'];
    }

从以上源码中很容易知道,选择的driver是redis,最后还是要调用\Illuminate\Session\SessionManager中的createRedisDriver()方法:

    protected function createRedisDriver()
    {
        /**
         * @var \Illuminate\Session\CacheBasedSessionHandler $handler
         */
        $handler = $this->createCacheHandler(\'redis\');

        // 设置redis连接
        $handler->getCache()->getStore()->setConnection($this->app[\'config\'][\'session.connection\']);

        return $this->buildSession($handler);
    }
    
    protected function createCacheHandler($driver)
    {
        // $store = \'redis\'
        $store = $this->app[\'config\']->get(\'session.store\') ?: $driver;

        $minutes = $this->app[\'config\'][\'session.lifetime\'];
        
        // $this->app[\'cache\']->store($store)返回\Illuminate\Cache\Repository实例
        return new CacheBasedSessionHandler(clone $this->app[\'cache\']->store($store), $minutes);
    }
    
    // Illuminate\Session\CacheBasedSessionHandler
    /**
     * Get the underlying cache repository.
     *
     * @return \Illuminate\Contracts\Cache\Repository|\Illuminate\Cache\Repository
     */
    public function getCache()
    {
        return $this->cache;
    }
    
    // \Illuminate\Cache\Repository
    /**
     * Get the cache store implementation.
     *
     * @return \Illuminate\Contracts\Cache\Store|RedisStore
     */
    public function getStore()
    {
        return $this->store;
    }
    
    // \Illuminate\Cache\RedisStore
    /**
     * Set the connection name to be used.
     *
     * @param  string  $connection
     * @return void
     */
    public function setConnection($connection)
    {
        $this->connection = $connection;
    }

从以上源码知道获取到\Illuminate\Session\CacheBasedSessionHandler这个handler后,就可以buildSession()了:

    protected function buildSession($handler)
    {
        // 设置加密的则返回EncryptedStore实例,这里假设没有加密
        if ($this->app[\'config\'][\'session.encrypt\']) {
            return new EncryptedStore(
                $this->app[\'config\'][\'session.cookie\'], $handler, $this->app[\'encrypter\']
            );
        } else {
            // 默认$this->app[\'config\'][\'session.cookie\'] === \'laravel_session\'
            return new Store($this->app[\'config\'][\'session.cookie\'], $handler);
        }
    }

从源码中可看出session实例就是\Illuminate\Session\Store实例,并且构造Store类还需要一个重要的部件handler,构造好了session实例后,就可以通过这个handler来从session存储的介质中如redis获取session数据了,这里设置的session driver是redis,所以handler就会是\Illuminate\Session\CacheBasedSessionHandler。总的来说,现在已经构造好了session实例即\Illuminate\Session\Store

然后第二步就是$session->start()从存储介质中加载session数据:

    public function start()
    {
        // 从存储介质中加载session数据
        $this->loadSession();
        
        // session存储介质中没有\'_token\'这个key就生成一个
        if (! $this->has(\'_token\')) {
            $this->regenerateToken();
        }

        return $this->started = true;
    }

关键是loadSession()的源码:

    // Illuminate/Session/Store
    protected function loadSession()
    {
        // 从redis中读取key为\'laravel_session\'的数据后存入session实例即Store的$attributes属性中
        $this->attributes = array_merge($this->attributes, $this->readFromHandler());

        foreach (array_merge($this->bags, [$this->metaBag]) as $bag) {
            /**
             * @var \Symfony\Component\HttpFoundation\Session\Storage\MetadataBag $bag
             */
            $this->initializeLocalBag($bag);

            $bag->initialize($this->bagData[$bag->getStorageKey()]);
        }
    }
    
    protected function readFromHandler()
    {
        // 主要是这句,通过handler从存储介质redis中读取session数据
        // $this->getId() === \'laravel_session\'
        $data = $this->handler->read($this->getId());

        if ($data) {
            $data = @unserialize($this->prepareForUnserialize($data));

            if ($data !== false && ! is_null($data) && is_array($data)) {
                return $data;
            }
        }

        return [];
    }

这里的handler是\Illuminate\Session\CacheBasedSessionHandler,看下该handler的read()源码:

    // $sessionId === \'laravel_session\'
    public function read($sessionId)
    {
        // 这里的cache是Illuminate\Cache\Repository
        return $this->cache->get($sessionId, \'\');
    }
    
    // Illuminate\Cache\Repository
    public function get($key, $default = null)
    {
        if (is_array($key)) {
            return $this->many($key);
        }

        // 这里的store是Illuminate\Cache\RedisStore
        $value = $this->store->get($this->itemKey($key));

        if (is_null($value)) {
            $this->fireCacheEvent(\'missed\', [$key]);

            $value = value($default);
        } else {
            $this->fireCacheEvent(\'hit\', [$key, $value]);
        }

        return $value;
    }
    
    // Illuminate\Cache\RedisStore
    public function get($key)
    {
        if (! is_null($value = $this->connection()->get($this->prefix.$key))) {
            return $this->unserialize($value);
        }
    }

通过以上代码,很容易了解从redis存储介质中加载key为\’laravel_session\’的数据,最后还是调用了RedisStore::get($key, $default)方法。

但不管咋样,通过handle()第一步$session = $this->startSession($request);就得到了session实例即Store,该步骤中主要做了两步:一是Store实例化;二是从redis中读取key为\’laravel_session\’的数据。

然后就是$this->collectGarbage($session)做了垃圾回收。中篇再聊。

总结:本文主要学习了session机制的启动工作中第一步session的实例化,主要包括两步骤:Store的实例化;从redis中读取key为laravel_session的数据。中篇再聊下session垃圾回收,和session的增删改查操作,到时见。

原文:https://segmentfault.com/a/1190000007090756

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