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 $response;
}
从Laravel学习笔记之Middleware源码解析这篇文章中知道,该中间件有前置操作和后置操作。看下sessionConfigured()
的源码:
/**
* Determine if a session driver has been configured.
*
* @return bool
*/
protected function sessionConfigured()
{
// 检查session.php中driver选项是否设置
return ! is_null(Arr::get($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。
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