Magento模块调用的过程和逻辑

1.在调用每个Magento模块(Modules)的时候，首先会返回Mage_Core_Model_Config 这个模型 它里面呈现了模块的一些常规配置，比如是否生效(enabled)，版本(version)等等。Mage_Core_Model_Congif这个模型中有这么一个方法，来完成上面所说的功能。

    /**     * Get module config node     *     * @param string $moduleName     * @return Varien_Simplexml_Object     */    function getModuleConfig($moduleName='')    {        $modules = $this->getNode('modules');        if (''===$moduleName) {            return $modules;        } else {            return $modules->$moduleName;        }    }

这个方法有一个参数，就是模块名，返回的对象是Varien_Simplexml_Object2.调用每个模块的时候，它只是会建立一个基本的结构，并不会调用模块自身的配置情况。_loadDeclaredModules这个方法来帮助完成上面所说的需求。

 /**     * Load declared modules configuration     *     * @param   null $mergeConfig depricated     * @return  Mage_Core_Model_Config     */    protected function _loadDeclaredModules($mergeConfig = null)    {        $moduleFiles = $this->_getDeclaredModuleFiles();        if (!$moduleFiles) {            return ;        }        Varien_Profiler::start('config/load-modules-declaration');        $unsortedConfig = new Mage_Core_Model_Config_Base();        $unsortedConfig->loadString('');        $fileConfig = new Mage_Core_Model_Config_Base();        // load modules declarations        foreach ($moduleFiles as $file) {            $fileConfig->loadFile($file);            $unsortedConfig->extend($fileConfig);        }        $moduleDepends = array();        foreach ($unsortedConfig->getNode('modules')->children() as $moduleName => $moduleNode) {            if (!$this->_isAllowedModule($moduleName)) {                continue;            }            $depends = array();            if ($moduleNode->depends) {                foreach ($moduleNode->depends->children() as $depend) {                    $depends[$depend->getName()] = true;                }            }            $moduleDepends[$moduleName] = array(                'module'    => $moduleName,                'depends'   => $depends,                'active'    => ('true' === (string)$moduleNode->active ? true : false),            );        }        // check and sort module dependence        $moduleDepends = $this->_sortModuleDepends($moduleDepends);        // create sorted config        $sortedConfig = new Mage_Core_Model_Config_Base();        $sortedConfig->loadString('');        foreach ($unsortedConfig->getNode()->children() as $nodeName => $node) {            if ($nodeName != 'modules') {                $sortedConfig->getNode()->appendChild($node);            }        }        foreach ($moduleDepends as $moduleProp) {            $node = $unsortedConfig->getNode('modules/'.$moduleProp['module']);            $sortedConfig->getNode('modules')->appendChild($node);        }        $this->extend($sortedConfig);        Varien_Profiler::stop('config/load-modules-declaration');        return $this;    }

从foreach ($moduleDepends as $moduleProp) 开始的这段代码可以看出，程序是对app\etc\modules这段代码做xml的解析3.loadBase()这个方法会对系统的配置文件进行加载和解析，比如config.xml和local.xml

    /**     * Load base system configuration (config.xml and local.xml files)     *     * @return Mage_Core_Model_Config     */    public function loadBase()    {        $etcDir = $this->getOptions()->getEtcDir();        $files = glob($etcDir.DS.'*.xml');        $this->loadFile(current($files));        while ($file = next($files)) {            $merge = clone $this->_prototype;            $merge->loadFile($file);            $this->extend($merge);        }        if (in_array($etcDir.DS.'local.xml', $files)) {            $this->_isLocalConfigLoaded = true;        }        return $this;    }

4.此后加载模块自身的配置由loadModulesConfiguration这个function来完成

    /**     * Iterate all active modules "etc" folders and combine data from     * specidied xml file name to one object     *     * @param   string $fileName     * @param   null|Mage_Core_Model_Config_Base $mergeToObject     * @return  Mage_Core_Model_Config_Base     */    public function loadModulesConfiguration($fileName, $mergeToObject = null, $mergeModel=null)    {        $disableLocalModules = !$this->_canUseLocalModules();        if ($mergeToObject === null) {            $mergeToObject = clone $this->_prototype;            $mergeToObject->loadString('');        }        if ($mergeModel === null) {            $mergeModel = clone $this->_prototype;        }        $modules = $this->getNode('modules')->children();        foreach ($modules as $modName=>$module) {            if ($module->is('active')) {                if ($disableLocalModules && ('local' === (string)$module->codePool)) {                    continue;                }                if (!is_array($fileName)) {                    $fileName = array($fileName);                }                foreach ($fileName as $configFile) {                    $configFile = $this->getModuleDir('etc', $modName).DS.$configFile;                    if ($mergeModel->loadFile($configFile)) {                        $mergeToObject->extend($mergeModel, true);                    }                }            }        }        return $mergeToObject;    }

5.最后的解析工作由loadFile来完成

    /**     * Imports XML file     *     * @param string $filePath     * @return boolean     */    public function loadFile($filePath)    {        if (!is_readable($filePath)) {            //throw new Exception('Can not read xml file '.$filePath);            return false;        }        $fileData = file_get_contents($filePath);        $fileData = $this->processFileData($fileData);        return $this->loadString($fileData, $this->_elementClass);    }

The End!