Detailed explanation of front-end controller pattern example

/*前端控制器的主要组成部分及功能如下: 1、入口文件类controller;(对这个系统的调用都是从这个文件开始的,也相当于一个控制中心，对所有相关的类进行调用) 2、应用程序配置信息类applicationhelper;(用于获取应用程序所需的配置信息) 3、命令类解释器commandresolver;(根据用户请求调用相应的命令类) 4、命令类command;(调用用户请求信息类和业务逻辑,还可以调用视图文件) 整个系统的调用步骤大概就是： 1、获取程序所需的配置信息 2、获取命令类 3、执行命令类 前端控制器与命令模式对比，在我看来二者基本没什么区别，原理大致相同。前端控制器的代码及注解如下：*/namespace woo\controller;//入口文件类class Controller {private $applicationHelper;private function __construct (); static function run(){$instance = new Controller();$instance->init();$instance->handleRequest(); } function init(){ //获取程序所需的配置信息 $applicationHelper = ApplicationHelper::instance();$applicationHelper->init(); } function handleRequest(){ //获取并执行命令类$request = new \woo\controller\Request();$cmd_r = new \woo\command\CommandResolver();$cmd = $cmd_r->getCommand($request);$cmd->execute($request); } }//获取应用程序配置信息class ApplicationHelper {private static $instance;private $config = "/tmp/data/woo_options.xml"; //配置信息保存的文件private function __construct (){} static function instance(){if(!self::$instance){ selff::$instance = new self(); }return self::$instance; } function init(){$dsn = \woo\base\ApplicatonRegistry::getDSN(); if(!is_null($dsn)){return; }$this->getOptions(); } private function getOptions(){$this->ensure(file_exists($this->config),"conld not find options file"); $options = SimpleXml_load_file($this->config);print get_class($options);$dsn = (string)$options->dsn;$this->ensure($dsn,"No DSN found"); \woo\base\ApplicationRegistry::setDSN($dsn); //配置信息将被缓存到一个注册表类中 //设置其他值 } private function ensure($expr,$message){if(!$expr){throw new \woo\base\AppException($message); } } }//用户请求信息类 class Request {private $properties;private $feedback =array();function __construct(){$this->init(); \woo\base\RequestRegistry::setRequest($this); } function init(){if(isset($_SERVER['REQUEST_METHOD'])){$this->properties = $_REQUEST;return; }foreach($_SERVER['argv'] as $arg){if(Strpos($arg,'=')){list($key,$val) = explode("=",$arg);$this->setProperty($key,$val); } } } function getProperty($key){if(isset($this->properties[$key]){return $this->properties[$key]; } } function setProperty($key,$val){$this->properties[$key] = $val; } function addFeedback($msg){array_push($this->feedback,$msg); } function getFeedback(){return $this->feedback; }function getFeedbackString($separator="\n"){return implode($separator,$this->feedback); } } namespace woo\command;//命令解释器 class CommandResolver{private static $base_cmd;private Static $default_cmd; function __construct (){if(!self::$base_cmd){//命令类的基类,这个主要将使用反射来检查找到的命令类是否是继承了它self::$base_cmd = new \ReflectionClass("\woo\command\Command"); self::$default_cmd = new DefaultCommand(); //默认的命令类，当找不到相应的命令类时将调用它 } } //获取命令类function getCommand(\woo\controller\Request $request){$cmd = $request->getProperty('cmd');$sep = DIRECTORY_SEPARATOR; //代表"/"if(!$cmd){return self::$default_cmd; }$cmd = str_replace(array('.',$sep),"",$cmd);$filepath = "woo{$sep}command{$sep}{$cmd}.php"; //命令类的文件路径$classname = "woo\\command\\{$cmd}"; //类名if(file_exists($filepath)){ @require_once("$filepath");if(class_exists($classname)){$cmd_class = new ReflectionClass($classname);if($cmd_class->isSubClassOf(self::$base_cmd)){return $cmd_class->newInstance(); //实例化命令类} else {$request->addFeedback("command '$cmd' is not a Command"); } } }$request->addFeedback("command '$cmd' not found");return clone self::$default_cmd; } }//命令类abstract class Command{final function __construct(){}function execute(\woo\controller\Request $request){$this->doExecute($request); }abstract function doExecute(\woo\controller\Request $request); }class DefaultCommand extends Command{function doExecute(\woo\controller\Request $request){$request->addFeedback("Welcome to Woo");include("woo/view/main.php"); } }//客户端require("woo/controller/Controller.php"); \woo\controller\Controller::run();