CodeIgniter框架源码解析九之路由类文件Router.php

前言

CI框架Router路由类将URI映射到对应的控制器及方法，Router类大量代码处理的是自定义路由，该类要支撑以下几个功能点：

• 自定义路由规则：在application/config/routes.php文件中的$route数组，利用它可以设置路由规则，在路由规则中可以使用通配符或正则表达式，比如：$route['product/:num'] = 'catalog/product_lookup'; $route['products/([a-z]+)/(\d+)'] = $1/id_$2;;
• 支持回调函数：在路由规则中使用回调函数来处理逆向引用，比如：$route['products/([a-zA-Z]+)/edit/(\d+)'] = function ($product_type, $id){return 'catalog/product_edit/' . strtolower($product_type) . '/' . $id;};;
• 支持使用HTTP动词：在路由数组后面再加一个键，键名为HTTP动词，可以使用标准的 HTTP 动词（GET、PUT、POST、DELETE、PATCH），也可以使用自定义的动词 （例如：PURGE），不区分大小写。比如：$route['products']['put'] = 'product/insert';；

⏸️这里不妨也先暂停思考下，如果要求支持以上的自定义路由规则，你写时要打算如何处理呢？。。。。。。

好，我们先看下CI框架中路由类的实现框架：

//CI_Config class object
public $config;
//List of routes
public $routes =	array();
//Current class name
public $class =		'';
//Current method name
public $method =	'index';
//Sub-directory that contains the requested controller class
public $directory;
// Default controller (and method if specific)
public $default_controller;
//Determines whether dashes in controller & method segments should be automatically replaced by underscores.
public $translate_uri_dashes = FALSE;
//Enable query strings flag Determines whether to use GET parameters or segment URIs
public $enable_query_strings = FALSE;

public function __construct(){...}
//Set route mapping
protected function _set_routing(){...}
//Set request route
protected function _set_request($segments = array()){...}
//Set default controller
protected function _set_default_controller(){...}
//Validate request
protected function _validate_request($segments){...}
//Parse routes
protected function _parse_routes(){...}

public function set_class($class){...}
public function fetch_class(){...}
public function set_method($method){...}
public function fetch_method(){...}
public function set_directory($dir, $append = FALSE){...}
public function fetch_directory(){...}

构造函数__contruct()

Router::class构造函数实例化的过程，就已经完成了路由的解析过程，得到请求的控制器和方法名。

public function __contruct($routing = NULL){
  $this->config =& load_class('Config', 'core');
  $this->uri =& load_class('URI', 'core');

  //确认是否开启querystirng模式，如果这个模式开启,那就用index.php?c=controller&m=method这样去访问控制器和方法了
  $this->enable_query_strings = ( ! is_cli() && $this->config->item('enable_query_strings') === TRUE);
  // If a directory override is configured, it has to be set before any dynamic routing logic
  // 通俗的说路由器在找控制器和方法时，会在‘controller/设置目录/’下寻找
  is_array($routing) && isset($routing['directory']) && $this->set_directory($routing['directory']);
  $this->_set_routing();

  // Set any routing overrides that may exist in the main index file
  if (is_array($routing)){
    empty($routing['controller']) OR $this->set_class($routing['controller']);
    empty($routing['function'])   OR $this->set_method($routing['function']);
  }

  log_message('info', 'Router Class Initialized');
}

核心解析函数_set_routing()

加载config file中自定义的路由规则，将uri string（$this->enable_query_strings=TRUE时路由直接从querystring中解析）通过_parse_routes()解析映射到合理的directory,class和method。

protected function _set_routing(){
  if (file_exists(APPPATH.'config/routes.php')){
    include(APPPATH.'config/routes.php');
  }
  if (file_exists(APPPATH.'config/'.ENVIRONMENT.'/routes.php')){
    include(APPPATH.'config/'.ENVIRONMENT.'/routes.php');
  }

  // Validate & get reserved routes
  if (isset($route) && is_array($route)){
    isset($route['default_controller']) && $this->default_controller = $route['default_controller'];
    //如果设置为TRUE，URI中的破折号转换成类名的下划线_
    isset($route['translate_uri_dashes']) && $this->translate_uri_dashes = $route['translate_uri_dashes'];
    unset($route['default_controller'], $route['translate_uri_dashes']);
    $this->routes = $route;
  }

  // Are query strings enabled in the config file? Normally CI doesn't utilize query strings
  // since URI segments are more search-engine friendly, but they can optionally be used.
  // index.php?d=admin&c=mall&m=list
  if ($this->enable_query_strings){
    if( ! isset($this->directory)){
      $_d = $this->config->item('directory_trigger');
      $_d = isset($_GET[$_d]) ? trim($_GET[$_d], " \t\n\r\0\x0B/") : '';
      if ($_d !== ''){
        $this->uri->filter_uri($_d);
        $this->set_directory($_d);
      }
    }
    //获取控制器和方法并设置$this->uri->rsegments
    $_c = trim($this->config->item('controller_trigger'));
    if ( ! empty($_GET[$_c])){
      $this->uri->filter_uri($_GET[$_c]);
      $this->set_class($_GET[$_c]);

      $_f = trim($this->config->item('function_trigger'));
      if ( ! empty($_GET[$_f])){
        $this->uri->filter_uri($_GET[$_f]);
        $this->set_method($_GET[$_f]);
      }

      $this->uri->rsegments = array(
        1 => $this->class,
        2 => $this->method
      );
    }else{
      $this->_set_default_controller();
    }
    // Routing rules don't apply to query strings and we don't need to detect
    // directories, so we're done here
    return;
  }

  //非querystring模式走到此处
  if ($this->uri->uri_string !== ''){
    $this->_parse_routes();
  }else{
    $this->_set_default_controller();
  }
}

解析自定义路由规则_parse_routes()

根据config/routes.php中自定义的路由规则【通配符和正则表达式，回调函数，HTTP动词】，逐个匹配$this->uri，若有命中则将此路由片段中传递给_set_request处理，否则直接将$this->uri->segments传递给_set_request。

protected function _parse_routes(){
  // Turn the segment array into a URI string
  $uri = implode('/', $this->uri->segments);
  $http_verb = isset($_SERVER['REQUEST_METHOD']) ? strtolower($_SERVER['REQUEST_METHOD']) : 'cli';

  // Loop through the route array looking for wildcards
  foreach ($this->routes as $key => $val){
    // Check if route format is using HTTP verbs
    if (is_array($val)){
      $val = array_change_key_case($val, CASE_LOWER);
      if (isset($val[$http_verb])){
        $val = $val[$http_verb];
      }else{
        continue;
      }
    }

    // Convert wildcards to RegEx
    $key = str_replace(array(':any', ':num'), array('[^/]+', '[0-9]+'), $key);
    if (preg_match('#^'.$key.'$#', $uri, $matches)){
      // Are we using callbacks to process back-references?
      if ( ! is_string($val) && is_callable($val)){
        array_shift($matches);
        $val = call_user_func_array($val, $matches);
      }elseif (strpos($val, '$') !== FALSE && strpos($key, '(') !== FALSE){
        // Are we using the default routing method for back-references?比如$route['products/([a-z]+)/(\d+)'] = $1/id_$2;
        $val = preg_replace('#^'.$key.'$#', $val, $uri);
      }

      $this->_set_request(explode('/', $val));
      return;
  }
}

  // If we got this far it means we didn't encounter a
  // matching route so we'll set the site default route
  $this->_set_request(array_values($this->uri->segments));
}

_set_request($segments)

首先调用$this->_validate_request解析segments目录，然后根据segments映射出控制器，方法名，并更新设置$this->uri->rsegments。

protected function _set_request($segments = array()){
  //检测寻找出一个正确存在的路由，确定后的值分别放到Rouer::$class这些属性中
  $segments = $this->_validate_request($segments);
  // If we don't have any segments left - try the default controller;
  // Directories get shifted out of the segments array!
  if (empty($segments)){
    $this->_set_default_controller();
    return;
  }

  //是否将路径中的‘-’映射至类名的下划线‘_’
  if ($this->translate_uri_dashes === TRUE){
    $segments[0] = str_replace('-', '_', $segments[0]);
    if (isset($segments[1])){
      $segments[1] = str_replace('-', '_', $segments[1]);
    }
  }

  $this->set_class($segments[0]);
  if (isset($segments[1])){
    $this->set_method($segments[1]);
  }else{
    $segments[1] = 'index';
  }

  array_unshift($segments, NULL);
  unset($segments[0]);
  $this->uri->rsegments = $segments;
}

_validate_request($segments)

检测寻找出一个正确存在的路由，主要是在于处理多级目录，重置$this->directory。

protected function _validate_request($segments){
  $c = count($segments);
  $directory_override = isset($this->directory);

  // Loop through our segments and return as soon as a controller
  // is found or when such a directory doesn't exist
  while ($c-- > 0){
    $test = $this->directory
      .ucfirst($this->translate_uri_dashes === TRUE ? str_replace('-', '_', $segments[0]) : $segments[0]);
      if ( ! file_exists(APPPATH.'controllers/'.$test.'.php')
        && $directory_override === FALSE
        && is_dir(APPPATH.'controllers/'.$this->directory.$segments[0])){
        $this->set_directory(array_shift($segments), TRUE);
        continue;
      }

      return $segments;
  }
  // This means that all segments were actually directories
  return $segments;
}

_set_default_controller()

由$this->default_controller，设置对应的控制器，方法和$this->uri->rsegments。

protected function _set_default_controller(){
  if (empty($this->default_controller)){
    show_error('Unable to determine what should be displayed. A default route has not been specified in the routing file.');
  }

  // Is the method being specified?
  if (sscanf($this->default_controller, '%[^/]/%s', $class, $method) !== 2){
  	$method = 'index';
  }

  if ( ! file_exists(APPPATH.'controllers/'.$this->directory.ucfirst($class).'.php')){
  	// This will trigger 404 later
  	return;
  }

  $this->set_class($class);
  $this->set_method($method);

  // Assign routed segments, index starting from 1
  $this->uri->rsegments = array(
  	1 => $class,
  	2 => $method
  );

  log_message('debug', 'No URI present. Default controller set.');
}

Route::class的属性函数簇

set_class($class),fetch_class();
set_method($method),fetch_method()
set_directory($dir, $append = FALSE)

public function set_class($class)
{
  $this->class = str_replace(array('/', '.'), '', $class);
}

public function fetch_class()
{
  return $this->class;
}

public function set_method($method)
{
  $this->method = $method;
}

public function fetch_method()
{
  return $this->method;
}

public function set_directory($dir, $append = FALSE)
{
  if ($append !== TRUE OR empty($this->directory)){
  	$this->directory = str_replace('.', '', trim($dir, '/')).'/';
  }else{
  	$this->directory .= str_replace('.', '', trim($dir, '/')).'/';
  }
}

总结

CI_Router路由类将uri string根据定义的路由规则（包括自定义路由规则）映射到对应的控制器及方法，待以后续调用处理请求。最后，我们再次来梳理下路由解析类的CI执行流程：

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