Laravel框架中Autoloader模块的代码分析

<?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(
	'SymfonyComponentConsole' 
                    => path('sys').'vendor/Symfony/Component/Console',
	'SymfonyComponentHttpFoundation'
                    => 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',
	),