CI框架源码解读--ROUTE和URL类

摘要：支持基于段方法和查询字符串方法两种形式的。里的方法就是利用类来实现解析出类名方法名。在类的构造函数里有一步方法代码如下如果你的原始是的话，经过这个方法处理，你会得到参考文章

路由的目的是为了从URL中解析出class类名是什么，method方法名是什么，所传的参数有哪些，参数值又是什么，类文件存在的路径是哪。最终实现方法的调度。

CI支持基于段方法和查询字符串方法两种形式的URL。

基于段形式：

example.com/news/article/my_article.html

查询字符串形式：

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

URL的获取方法有如下几种：PATH_INFO、QUERY_STRING、REQUEST_URI、ORIG_PATH_INFO。比较常用的是PATH_INFO。几种方式的差异可以简单通过打印$_SERVER来查看。比如xxx.com/welcome/test_search.html?c=welcome&d=test_search，打印的结果是（只挑了这几部分）：

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
)

下面是源码config文件里关于这几种方法的定义。

/*
|--------------------------------------------------------------------------
| 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";

我们这里用的也是PATH_INFO来获取。

至此，我们就拥有了URL地址，接下来我们就要分析地址。URL类就是来做分析的事情。

system/core/Router.php里的_set_routing()方法就是利用URL类来实现解析出类名方法名。

看下代码（下面的代码都是CodeIgniter-3.0.6版本的），英文注释已经很详细了，我在关键点额外加了点中文注释：

/**
 * 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
    // 这段不用看，我们项目中是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], " 	

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?
    //这里的$this->uri是route类构造函数里面$this->uri =& load_class("URI", "core");来的，后文我们会详细看URI类
    if ($this->uri->uri_string !== "")
    {
        //绝大多数情况是会走这里
        $this->_parse_routes();
    }
    else
    {
        $this->_set_default_controller();
    }

所以我们重点再看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我们后面也会讲到
    $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文件里的配置
    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]);
        }
    }

    //找到类名了
    $this->set_class($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;

到这里，就根据URL找出了类名和方法名，在引导文件system/core/CodeIgniter.php里面就可以实现调度了。

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

$CI = new $class();

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

下面我们看下URI类，来看看上面代码里的$this->uri等各项是怎么得到的。

在URI类的构造函数里有一步：

$this->_set_uri_string($uri)

_set_uri_string()方法代码如下：

/**
 * 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]);
    }
}

如果你的原始uri是http://example.com/index.php/news/local/metro/crime_is_up的话，经过这个_set_uri_string()方法处理，你会得到$this->segments = array([1]=>"news", [2]=>"local",[3]=>"metro",[4]=>"crime_is_up")

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