Code analysis of Autoloader module in Laravel framework

<?php namespace Laravel;

class Autoloader {

    /**

     * 类名到文件名得映射

     *

     * @var array

     */

    public static $mappings = array();

    /**

     * PSR-0命名转换目录

     *

     * @var array

     */

    public static $directories = array();

    /**

     * 命名空间和目录的映射

     *

     * @var array

     */

    public static $namespaces = array();

    /**

     * 下划线类库和目录映射

     *

     * @var array

     */

    public static $underscored = array();

    /**

     * 自动加载类的别名

     *

     * @var array

     */

    public static $aliases = array();

    /**

     * Load the file corresponding to a given class.

     *

     * This method is registered in the bootstrap file as an SPL auto-loader.

     *

     * @param  string  $class

     * @return void

     */

    public static function load($class)

    {

        // 尝试类是否有别名

        if (isset(static::$aliases[$class]))

        {

            return class_alias(static::$aliases[$class], $class);

        }

        // 查找映射

        elseif (isset(static::$mappings[$class]))

        {

            require static::$mappings[$class];

            return;

        }

        // 加载这个新的类

        foreach (static::$namespaces as $namespace => $directory)

        {

            # 支持函数 是否命名空间开头 在helpers.php中

            if (starts_with($class, $namespace))

            {

                return static::load_namespaced($class, $namespace, $directory);

            }

        }

        static::load_psr($class);

    }

    /**

     * 从给定的目录加载命名空间

     *

     * @param  string  $class

     * @param  string  $namespace

     * @param  string  $directory

     * @return void

     */

    protected static function load_namespaced($class, $namespace, $directory)

    {

        return static::load_psr(substr($class, strlen($namespace)), $directory);

    }

    /**

     * 使用PSR-0标准来试图解析一个类

     *

     * @param  string  $class

     * @param  string  $directory

     * @return void

     */

    protected static function load_psr($class, $directory = null)

    {

        // 用PSR-0来解析类 使之变成路径字符串

        $file = str_replace(array('\\', '_'), '/', $class);

        $directories = $directory ?: static::$directories; // 获得类路径

        $lower = strtolower($file); # 默认全部小写

        // 尝试解析

        foreach ((array) $directories as $directory)

        {

            if (file_exists($path = $directory.$lower.EXT))

            {

                return require $path;

            }

            elseif (file_exists($path = $directory.$file.EXT))

            {

                return require $path;

            }

        }

    }

    /**

     * 注册一个数组 包含类路径映射

     *

     * @param  array  $mappings

     * @return void

     */

    public static function map($mappings)

    {

        static::$mappings = array_merge(static::$mappings, $mappings);

    }

    /**

     * 注册类的别名

     *

     * @param  string  $class

     * @param  string  $alias

     * @return void

     */

    public static function alias($class, $alias)

    {

        static::$aliases[$alias] = $class;

    }

    /**

     * 注册目录

     *

     * @param  string|array  $directory

     * @return void

     */

    public static function directories($directory)

    {

        $directories = static::format($directory);

        static::$directories = array_unique(array_merge(static::$directories, $directories));

    }

    /**

     * 映射命名空间和目录

     *

     * @param  array   $mappings

     * @param  string  $append

     * @return void

     */

    public static function namespaces($mappings, $append = '\\')

    {

        $mappings = static::format_mappings($mappings, $append);

        static::$namespaces = array_merge($mappings, static::$namespaces); # 合并之后: (array "命名空间", array "命名空间","路径")

    }

    /**

     * 注册下划线命名空间

     *

     * @param  array  $mappings

     * @return void

     */

    public static function underscored($mappings)

    {

        static::namespaces($mappings, '_'); # 下划线风格

    }

    /**

     * 格式目录映射

     *

     * @param  array   $mappings

     * @param  string  $append

     * @return array

     */

    protected static function format_mappings($mappings, $append)

    {

        foreach ($mappings as $namespace => $directory)

        {

            # 清理命名空间

            $namespace = trim($namespace, $append).$append;

            unset(static::$namespaces[$namespace]); # 去除之前的 如果存在的话

            $namespaces[$namespace] = head(static::format($directory)); # 一个命名空间只能对应一个目录

        }

        return $namespaces;

    }

    /**

     * 格式化一个目录数组

     *

     * @param  array  $directories

     * @return array

     */

    protected static function format($directories)

    {

        return array_map(function($directory)

        {

            return rtrim($directory, DS).DS;# 清理目录

        }, (array) $directories); // 用map遍历目录数组

    }

}

spl_autoload_register(array('Laravel\\Autoloader', 'load')); # spl_autoload_register array 命名空间,具体方法

Autoloader::namespaces(array('Laravel' => path('sys'))); # 定义Laravel系统根目录映射

# 定义EloquentORM框架

Autoloader::map(array(

    'Laravel\\Database\\Eloquent\\Relationships\\Belongs_To'

                    => path('sys').'database/eloquent/relationships/belongs_to'.EXT,

    'Laravel\\Database\\Eloquent\\Relationships\\Has_Many'

                    => path('sys').'database/eloquent/relationships/has_many'.EXT,

    'Laravel\\Database\\Eloquent\\Relationships\\Has_Many_And_Belongs_To'

                    => path('sys').'database/eloquent/relationships/has_many_and_belongs_to'.EXT,

    'Laravel\\Database\\Eloquent\\Relationships\\Has_One'

                    => path('sys').'database/eloquent/relationships/has_one'.EXT,

    'Laravel\\Database\\Eloquent\\Relationships\\Has_One_Or_Many'

                    => path('sys').'database/eloquent/relationships/has_one_or_many'.EXT,

));

# Symfony组件加载

Autoloader::namespaces(array(

    'Symfony\Component\Console'

                    => path('sys').'vendor/Symfony/Component/Console',

    'Symfony\Component\HttpFoundation'

                    => path('sys').'vendor/Symfony/Component/HttpFoundation',

));

'aliases' => array(

        'Auth'          => 'Laravel\\Auth',

        'Authenticator' => 'Laravel\\Auth\\Drivers\\Driver',

        'Asset'         => 'Laravel\\Asset',

        'Autoloader'    => 'Laravel\\Autoloader',

        'Blade'         => 'Laravel\\Blade',

        'Bundle'        => 'Laravel\\Bundle',

        'Cache'         => 'Laravel\\Cache',

        'Config'        => 'Laravel\\Config',

        'Controller'    => 'Laravel\\Routing\\Controller',

        'Cookie'        => 'Laravel\\Cookie',

        'Crypter'       => 'Laravel\\Crypter',

        'DB'            => 'Laravel\\Database',

        'Eloquent'      => 'Laravel\\Database\\Eloquent\\Model',

        'Event'         => 'Laravel\\Event',

        'File'          => 'Laravel\\File',

        'Filter'        => 'Laravel\\Routing\\Filter',

        'Form'          => 'Laravel\\Form',

        'Hash'          => 'Laravel\\Hash',

        'HTML'          => 'Laravel\\HTML',

        'Input'         => 'Laravel\\Input',

        'IoC'           => 'Laravel\\IoC',

        'Lang'          => 'Laravel\\Lang',

        'Log'           => 'Laravel\\Log',

        'Memcached'     => 'Laravel\\Memcached',

        'Paginator'     => 'Laravel\\Paginator',

        'Profiler'      => 'Laravel\\Profiling\\Profiler',

        'URL'           => 'Laravel\\URL',

        'Redirect'      => 'Laravel\\Redirect',

        'Redis'         => 'Laravel\\Redis',

        'Request'       => 'Laravel\\Request',

        'Response'      => 'Laravel\\Response',

        'Route'         => 'Laravel\\Routing\\Route',

        'Router'        => 'Laravel\\Routing\\Router',

        'Schema'        => 'Laravel\\Database\\Schema',

        'Section'       => 'Laravel\\Section',

        'Session'       => 'Laravel\\Session',

        'Str'           => 'Laravel\\Str',

        'Task'          => 'Laravel\\CLI\\Tasks\\Task',

        'URI'           => 'Laravel\\URI',

        'Validator'     => 'Laravel\\Validator',

        'View'          => 'Laravel\\View',

    ),