CI框架源碼解讀--ROUTE和URL類

路由的目的是爲了從URL中解析出class類名是什麼，method方法名是什麼，所傳的參數有哪些，參數值又是什麼，類文件存在的路徑是哪。最終實現方法的調度。

CI支持基於段方法和查詢字符串方法兩種形式的URL。

基於段形式：

example.com/news/article/my_article.html

查詢字符串形式：

index.php?c=products&m=view&id=345

URL的獲取方法有以下幾種：PATH_INFO、QUERY_STRING、REQUEST_URI、ORIG_PATH_INFO。比較經常使用的是PATH_INFO。幾種方式的差別能夠簡單經過打印$_SERVER來查看。好比xxx.com/welcome/test_search.html?c=welcome&d=test_search，打印的結果是（只挑了這幾部分）：

Array
(
    [QUERY_STRING] => c=welcome&d=test_search
    [REQUEST_URI] => /welcome/test_search.html?c=welcome&d=test_search
    [PATH_INFO] => /welcome/test_search.html
)

下面是源碼config文件裏關於這幾種方法的定義。

/*
|--------------------------------------------------------------------------
| URI PROTOCOL
|--------------------------------------------------------------------------
|
| This item determines which server global should be used to retrieve the
| URI string.  The default setting of 'AUTO' works for most servers.
| If your links do not seem to work, try one of the other delicious flavors:
|
| 'AUTO'            Default - auto detects
| 'PATH_INFO'       Uses the PATH_INFO
| 'QUERY_STRING'    Uses the QUERY_STRING
| 'REQUEST_URI'     Uses the REQUEST_URI
| 'ORIG_PATH_INFO'  Uses the ORIG_PATH_INFO
|
*/
$config['uri_protocol'] = 'PATH_INFO';

咱們這裏用的也是PATH_INFO來獲取。

至此，咱們就擁有了URL地址，接下來咱們就要分析地址。URL類就是來作分析的事情。

system/core/Router.php裏的_set_routing()方法就是利用URL類來實現解析出類名方法名。

看下代碼（下面的代碼都是CodeIgniter-3.0.6版本的），英文註釋已經很詳細了，我在關鍵點額外加了點中文註釋：

/**
 * Set route mapping
 *
 * Determines what should be served based on the URI request,
 * as well as any "routes" that have been set in the routing config file.
 *
 * @return    void
 */
protected function _set_routing()
{
    // Load the routes.php file. It would be great if we could
    // skip this for enable_query_strings = TRUE, but then
    // default_controller would be empty ...
    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 = $route['default_controller'];
        isset($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.
    // If this feature is enabled, we will gather the directory/class/method a little differently
    // 這段不用看，咱們項目中是FALSE
    if ($this->enable_query_strings)
    {
        // If the directory is set at this time, it means an override exists, so skip the checks
        if ( ! isset($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);
            }
        }

        $_c = trim($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;
    }

    // Is there anything to parse?
    //這裏的$this->uri是route類構造函數裏面$this->uri =& load_class('URI', 'core');來的，後文咱們會詳細看URI類
    if ($this->uri->uri_string !== '')
    {
        //絕大多數狀況是會走這裏
        $this->_parse_routes();
    }
    else
    {
        $this->_set_default_controller();
    }

因此咱們重點再看ROUTE的_parse_routes()方法：

/**
 * Parse Routes
 *
 * Matches any routes that may exist in the config/routes.php file
 * against the URI to determine if the class/method need to be remapped.
 *
 * @return    void
 */
protected function _parse_routes()
{
    // Turn the segment array into a URI string
    // $this->uri->segments咱們後面也會講到
    $uri = implode('/', $this->uri->segments);

    // Get HTTP verb
    $http_verb = isset($_SERVER['REQUEST_METHOD']) ? strtolower($_SERVER['REQUEST_METHOD']) : 'cli';

    // Loop through the route array looking for wildcards
    // 查看是否符合config文件裏的配置
    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);

        // Does the RegEx match?
        if (preg_match('#^'.$key.'$#', $uri, $matches))
        {
            // Are we using callbacks to process back-references?
            if ( ! is_string($val) && is_callable($val))
            {
                // Remove the original string from the matches array.
                array_shift($matches);

                // Execute the callback using the values in matches as its parameters.
                $val = call_user_func_array($val, $matches);
            }
            // Are we using the default routing method for back-references?
            elseif (strpos($val, '$') !== FALSE && strpos($key, '(') !== FALSE)
            {
                $val = preg_replace('#^'.$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));
}

再看_set_request()方法：

/**
 * Set request route
 *
 * Takes an array of URI segments as input and sets the class/method
 * to be called.
 *
 * @used-by    CI_Router::_parse_routes()
 * @param    array    $segments    URI segments
 * @return    void
 */
protected function _set_request($segments = array())
{
    $segments = $this->_validate_request($segments);
    // If we don't have any segments left - try the default controller;
    // WARNING: Directories get shifted out of the segments array!
    if (empty($segments))
    {
        $this->_set_default_controller();
        return;
    }

    if ($this->translate_uri_dashes === TRUE)
    {
        $segments[0] = str_replace('-', '_', $segments[0]);
        if (isset($segments[1]))
        {
            $segments[1] = str_replace('-', '_', $segments[1]);
        }
    }

    //找到類名了
    $this->set_class($segments[0]);
    if (isset($segments[1]))
    {
        //找到方法名了
        $this->set_method($segments[1]);
    }
    else
    {
        $segments[1] = 'index';
    }

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

到這裏，就根據URL找出了類名和方法名，在引導文件system/core/CodeIgniter.php裏面就能夠實現調度了。

$class = ucfirst($RTR->class);
$method = $RTR->method;

$CI = new $class();

/*
 * ------------------------------------------------------
 *  Call the requested method
 * ------------------------------------------------------
 */
call_user_func_array(array(&$CI, $method), $params);

下面咱們看下URI類，來看看上面代碼裏的$this->uri等各項是怎麼獲得的。

在URI類的構造函數裏有一步：

$this->_set_uri_string($uri)

_set_uri_string()方法代碼以下：

/**
 * Set URI String
 *
 * @param     string    $str
 * @return    void
 */
protected function _set_uri_string($str)
{
    // Filter out control characters and trim slashes
    $this->uri_string = trim(remove_invisible_characters($str, FALSE), '/');

    if ($this->uri_string !== '')
    {
        // Remove the URL suffix, if present
        if (($suffix = (string) $this->config->item('url_suffix')) !== '')
        {
            $slen = strlen($suffix);

            if (substr($this->uri_string, -$slen) === $suffix)
            {
                $this->uri_string = substr($this->uri_string, 0, -$slen);
            }
        }

        $this->segments[0] = NULL;
        // Populate the segments array
        foreach (explode('/', trim($this->uri_string, '/')) as $val)
        {
            $val = trim($val);
            // Filter segments for security
            $this->filter_uri($val);

            if ($val !== '')
            {
                $this->segments[] = $val;
            }
        }

        unset($this->segments[0]);
    }
}

若是你的原始uri是http://example.com/index.php/news/local/metro/crime_is_up的話，通過這個_set_uri_string()方法處理，你會獲得$this->segments = array([1]=>'news', [2]=>'local',[3]=>'metro',[4]=>'crime_is_up')

參考文章

• http://codeigniter.org.cn/use...

• http://codeigniter.org.cn/use...

• http://codeigniter.org.cn/use...