前端控制器模式实例详解

/*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();