[php]标记映射和工作单元
标记映射
系统中可能存在两个值相同,但又不是同一个引用的对象,这样的重复对象可能是从数据库中读出来的,这样就造成了不必要的查询。
标记映射是一个类ObjectWatcher,它负责管理进程中的领域对象,以保证进程中不出现重复对象。
标记映射可以防止重新读取数据库查询数据,只有当ObjectWatcher类中不存在标记映射对应的对象时才去查询数据库。这样就保证了在一个进程中,一条数据只对应一个对象。
代码很容易懂,都是一些存取数组值的操作。
ObjectWatcher代码:
namespace demo\domain; use \demo\domain\DomainObject; /** * 标记映射 */ class ObjectWatcher { private static $instance; // 标记映射 private $all = array(); private function __construct() { } public static function getInstance() { if (!isset(self::$instance)) { self::$instance = new self(); } return self::$instance; } /** * 获得对象对应的键值 * @param DomainObject $obj */ public function getGobalKey(DomainObject $obj) { $key = get_class($obj) . '_' . $obj->getId(); return $key; } /** * 添加到all * @param DomainObject $obj */ public static function add(DomainObject $obj) { $instance = self::getInstance(); $key = $instance->getGobalKey($obj); $instance->all[$key] = $obj; } /** * 从all中删除 * @param DomainObject $obj */ public static function delete(DomainObject $obj) { $instance = self::getInstance(); $key = $instance->getGobalKey($obj); unset($instance->all[$key]); } /** * 判断标记是否存在 * @param string $className * @param int $id */ public static function exists($className, $id) { $instance = self::getInstance(); $key = "{$className}_{$id}"; if (isset($instance->all[$key])) { return $instance->all[$key]; } return null; } }那么在哪里做标记呢?当然是生成查询对象的地方,分别有Mapper::find()、Mapper::insert()、Mapper::createObject()。 Mapper中新增加了addToMap()和getFromMap()。(其它方法没有改变,所以看以忽略吧。)
Mapper代码:
namespace demo\mapper; use \demo\base\AppException; use \demo\base\ApplicationRegistry; use \demo\domain\DomainObject; use \demo\domain\ObjectWatcher; /** * Mapper */ abstract class Mapper { // PDO protected static $PDO; // config protected static $dsn, $dbUserName, $dbPassword; // PDO选项 protected static $options = array( \PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8', \PDO::ATTR_ERRMODE, \PDO::ERRMODE_EXCEPTION, ); public function __construct() { if (!isset(self::$PDO)) { // ApplicationRegistry获取数据库连接信息 $appRegistry = ApplicationRegistry::getInstance(); self::$dsn = $appRegistry->getDsn(); self::$dbUserName = $appRegistry->getDbUserName(); self::$dbPassword = $appRegistry->getDbPassword(); if (!self::$dsn || !self::$dbUserName || !self::$dbPassword) { throw new AppException('Mapper init failed!'); } self::$PDO = new \PDO(self::$dsn, self::$dbUserName, self::$dbPassword, self::$options); } } /** * 查找指定ID * @param int $id */ public function findById($id) { // 从ObjectWatcher中获取 $obj = $this->getFromMap($id); if (!is_null($obj)) { return $obj; } $pStmt = $this->getSelectStmt(); $pStmt->execute(array($id)); $data = $pStmt->fetch(); $pStmt->closeCursor(); if (!is_array($data) || !isset($data['id'])) { return $obj; } $obj = $this->createObject($data); return $obj; } /** * 返回Collection */ public function findAll() { $pStmt = $this->getSelectAllStmt(); $pStmt->execute(array()); $raws = $pStmt->fetchAll(\PDO::FETCH_ASSOC); $collection = $this->getCollection($raws); return $collection; } /** * 插入数据 * @param \demo\domain\DomainObject $obj */ public function insert(DomainObject $obj) { $flag = $this->doInsert($obj); // 保存或者更新ObjectWatcher的$all[$key]的对象 $this->addToMap($obj); return $flag; } /** * 更新对象 * @param \demo\domain\DomainObject $obj */ public function update(\demo\domain\DomainObject $obj) { $flag = $this->doUpdate($obj); return $flag; } /** * 删除指定ID * @param int $id */ public function deleteById($id) { $pStmt = $this->getDeleteStmt(); $flag = $pStmt->execute(array($id)); return $flag; } /** * 生成一个$data中值属性的对象 * @param array $data */ public function createObject(array $data) { // 从ObjectWatcher中获取 $obj = $this->getFromMap($data['id']); if (!is_null($obj)) { return $obj; } // 创建对象 $obj = $this->doCreateObject($data); // 添加到ObjectWatcher $this->addToMap($obj); return $obj; } /** * 返回对应key标记的对象 * @param int $id */ private function getFromMap($id) { return ObjectWatcher::exists($this->getTargetClass(), $id); } /** * 添加对象到标记映射ObjectWatcher类 * @param DomainObject $obj */ private function addToMap(DomainObject $obj) { return ObjectWatcher::add($obj); } /** * 返回子类Collection * @param array $raw */ public function getCollection(array $raws) { return $this->getFactory()->getCollection($raws); } /** * 返回子类持久化工厂对象 */ public function getFactory() { return PersistanceFactory::getFactory($this->getTargetClass()); } protected abstract function doInsert(\demo\domain\DomainObject $obj); protected abstract function doCreateObject(array $data); protected abstract function getSelectStmt(); protected abstract function getSelectAllStmt(); protected abstract function doUpdate(\demo\domain\DomainObject $obj); protected abstract function getDeleteStmt(); protected abstract function getTargetClass(); }大部分代码是之前的,修改的只是一小部分。下面图一张:
现在,当Mapper从数据库中取出的数据映射成的对象都被标记到ObjectWatcher了,而且不需要对对象手动操作标记到ObjectWatcher,Mapper就已经帮你完成了。这样带来的好处是可以减少对数据库的操作和新对象的创建,比如find、createObject。但这也许可能带来问题,如果你的程序需要并发处理数据,那么被标记的对象数据就可能不一致了,你在这个时候可能需要对数据加锁。
工作单元
有些时候,我们可能没有改变数据的任何值却向数据库多次保存该数据,这当然是不必要的吧。工作单元可以使你只保存那些需要的对象。工作单元可以在一次请求即将结束时,把在这次请求中发生变化的对象保存到数据库中。一次请求的最后是在控制器(Controller)调用完Command和View之后,那么我们就可以在这里让工作单元执行任务。
标记映射的作用是在处理过程开始时向数据库加载不必要的对象,而工作单元则是在处理过程之后防止不必要的对象保存到数据库中。这两个工作方式就像是互补的。
为了判断哪些数据库的操作是必要的,那就需要跟踪与对象相关的各种事件(比如:setter()重新设置了对象的属性值)。跟踪工作当然最好放在被跟踪的对象中。
修改过的ObjectWatcher类:
namespace demo\domain; use \demo\domain\DomainObject; /** * 标记映射 */ class ObjectWatcher { private static $instance; // 标记映射 private $all = array(); // 保存新建对象 private $new = array(); // 保存被修改过的对象(“脏对象”) private $dirty = array(); // 保存删除对象 private $delete = array(); private function __construct() { } public static function getInstance() { if (!isset(self::$instance)) { self::$instance = new self(); } return self::$instance; } /** * 获得对象对应的键值 * @param DomainObject $obj */ public function getGobalKey(DomainObject $obj) { $key = get_class($obj) . '_' . $obj->getId(); return $key; } /** * 添加到all * @param DomainObject $obj */ public static function add(DomainObject $obj) { $instance = self::getInstance(); $key = $instance->getGobalKey($obj); $instance->all[$key] = $obj; } /** * 从all中删除 * @param DomainObject $obj */ public static function delete(DomainObject $obj) { $instance = self::getInstance(); $key = $instance->getGobalKey($obj); unset($instance->all[$key]); } /** * 添加到new * @param DomianObject $obj */ public static function addNew(DomainObject $obj) { $instance = self::getInstance(); $instance->new[] = $obj; } /** * 添加到dirty * @param DomianObject $obj */ public static function addDirty(DomainObject $obj) { $instance = self::getInstance(); if (!in_array($obj, $instance->dirty, true)) { $instance->dirty[$instance->getGobalKey($obj)] = $obj; } } /** * 添加到delete * @param DomainObject $obj */ public static function addDelete(DomainObject $obj) { $instance = self::getInstance(); $instance->delete[$instance->getGobalKey($obj)] = $obj; } /** * 清除标记dirty new delete * @param DomainObject $obj */ public static function addClean(DomainObject $obj) { $instance = self::getInstance(); // unset删除保存的对象 unset($instance->dirty[$instance->getGobalKey($obj)]); unset($instance->delete[$instance->getGobalKey($obj)]); // 删除new中的对象 $instance->new = array_filter($instance->new, function($a) use ($obj) { return !($a === $obj); }); } /** * 判断标记是否存在 * @param string $className * @param int $id */ public static function exists($className, $id) { $instance = self::getInstance(); $key = "{$className}_{$id}"; if (isset($instance->all[$key])) { return $instance->all[$key]; } return null; } /** * 对new dirty delete 中的标记对象执行操作 */ public function performOperations() { $instance = self::getInstance(); // new foreach ($instance->new as $obj) { $obj->finder()->insert($obj); } // dirty foreach ($instance->dirty as $obj) { $obj->finder()->update($obj); } // delete foreach ($instance->delete as $obj) { $obj->finder()->delete($obj); } $this->new = array(); $this->dirty = array(); $this->delete = array(); } }ObjectWatcher依然是标记映射,只是在这里增加了跟踪系统中对象的变化的功能。ObjectWatcher类提供了查找、删除、添加对象到数据库的机制。
由于ObjectWatcher的操作上对对象的操作,所以由这些对象自己来来执行ObjectWatcher是很适合的。
修改过的DomainObject类(markNew()、markDirty()、markDelete()、markClean()):
namespace demo\domain; use \demo\domain\HelperFactory; use \demo\domain\ObjectWatcher; /** * 领域模型抽象基类 */ abstract class DomainObject { protected $id = -1; public function __construct($id = null) { if (is_null($id)) { // 标记为new 新建 $this->markNew(); } else { $this->id = $id; } } public function getId() { return $this->id; } public function setId($id) { $this->id = $id; $this->markDirty(); } public function markNew() { ObjectWatcher::addNew($this); } public function markDirty() { ObjectWatcher::addDirty($this); } public function markDeleted() { ObjectWatcher::addDelete($this); } public function markClean() { ObjectWatcher::addClean($this); } public static function getCollection($type) { return HelperFactory::getCollection($type); } public function collection() { return self::getCollection(get_class($this)); } public static function getFinder($type) { return HelperFactory::getFinder($type); } public function finder() { return self::getFinder(get_class($this)); } }DomainObject和ObjectWatcher的关系图一张:

修改过的Mapper(和上面相同部分略去了,太占位子了):
/** * Mapper */ abstract class Mapper { //... /** * 查找指定ID * @param int $id */ public function findById($id) { // 从ObjectWatcher中获取 $obj = $this->getFromMap($id); if (!is_null($obj)) { return $obj; } $pStmt = $this->getSelectStmt(); $pStmt->execute(array($id)); $data = $pStmt->fetch(); $pStmt->closeCursor(); if (!is_array($data) || !isset($data['id'])) { return $obj; } $obj = $this->createObject($data); return $obj; } /** * 插入数据 * @param \demo\domain\DomainObject $obj */ public function insert(DomainObject $obj) { $flag = $this->doInsert($obj); // 保存或者更新ObjectWatcher的$all[$key]的对象 $this->addToMap($obj); $obj->markClean(); // 调试用的 echo 'insert :' . get_class($obj) . '_' . $obj->getName() . '_' . $obj->getId() .'<br>'; return $flag; } /** * 更新对象 * @param \demo\domain\DomainObject $obj */ public function update(\demo\domain\DomainObject $obj) { $flag = $this->doUpdate($obj); $obj->markClean(); // 调试用的 echo 'update :' . get_class($obj) . '_' . $obj->getName() . '_' . $obj->getId() .'<br>'; return $flag; } /** * 生成一个$data中值属性的对象 * @param array $data */ public function createObject(array $data) { // 从ObjectWatcher中获取 $obj = $this->getFromMap($data['id']); if (!is_null($obj)) { return $obj; } // 创建对象 $obj = $this->doCreateObject($data); // 添加到ObjectWatcher $this->addToMap($obj); // 清除new标记 ObjectWatcher::addClean($obj); return $obj; } //... }可以看到Mapper中修改的部分都是有改变对象的事件发生,即find()、update()、insert()、delete()。
对象的变化都能被跟踪到了,那么应该在哪里处理这些变化过的对象(“脏数据”)呢?上面说到了,应该在一次请求即将完成的时候。
一次请求即将结束时,Controller中调用工作单元(同样省略了没改变的代码):
namespace demo\controller; /** * Controller */ class Controller { // ... private function handleReuqest() { $request = new \demo\controller\Request(); $appController = \demo\base\ApplicationRegistry::getInstance()->getAppController(); // 执行完所有Command,有可能存在forward while ($cmd = $appController->getCommand($request)) { // var_dump($cmd); $cmd->execute($request); // 把当前Command设为已执行过 $request->setLastCommand($cmd); } // 工作单元执行任务 ObjectWatcher::getInstance()->performOperations(); // 获取视图 $view = $appController->getView($request); // 显示视图 $this->invokeView($view); } // ... }ObjectWatcher::getInstance()->performOperations()
好的,现在来个使用例子吧:
namespace demo\command; use demo\domain\Classroom; use demo\base\ApplicationRegistry; use demo\domain\ObjectWatcher; use demo\domain\HelperFactory; class Test extends Command { protected function doExecute(\demo\controller\Request $request) { $crMapper = HelperFactory::getFinder('demo\domain\Classroom'); // 新创建的对象 markNew() $crA = new Classroom(); $crA->setName('四年(3)班'); // 修改后的“脏”数据 $crB = $crMapper->findById(1); $crB->setName("五年(2)班"); } }输入的Url:
localhost/demo/runner.php?cmd=Test输出结果与预期的一样:
insert :demo\domain\Classroom_四年(3)班_58 update :demo\domain\Classroom_五年(2)班_1
现在对领域对象的管理有了较大的改进了。还有,我们使用模式的目的是提高效率,而不是降低效率。

TomodifydatainaPHPsession,startthesessionwithsession_start(),thenuse$_SESSIONtoset,modify,orremovevariables.1)Startthesession.2)Setormodifysessionvariablesusing$_SESSION.3)Removevariableswithunset().4)Clearallvariableswithsession_unset().5)Destroythe

Arrays can be stored in PHP sessions. 1. Start the session and use session_start(). 2. Create an array and store it in $_SESSION. 3. Retrieve the array through $_SESSION. 4. Optimize session data to improve performance.

PHP session garbage collection is triggered through a probability mechanism to clean up expired session data. 1) Set the trigger probability and session life cycle in the configuration file; 2) You can use cron tasks to optimize high-load applications; 3) You need to balance the garbage collection frequency and performance to avoid data loss.

Tracking user session activities in PHP is implemented through session management. 1) Use session_start() to start the session. 2) Store and access data through the $_SESSION array. 3) Call session_destroy() to end the session. Session tracking is used for user behavior analysis, security monitoring, and performance optimization.

Using databases to store PHP session data can improve performance and scalability. 1) Configure MySQL to store session data: Set up the session processor in php.ini or PHP code. 2) Implement custom session processor: define open, close, read, write and other functions to interact with the database. 3) Optimization and best practices: Use indexing, caching, data compression and distributed storage to improve performance.

PHPsessionstrackuserdataacrossmultiplepagerequestsusingauniqueIDstoredinacookie.Here'showtomanagethemeffectively:1)Startasessionwithsession_start()andstoredatain$_SESSION.2)RegeneratethesessionIDafterloginwithsession_regenerate_id(true)topreventsessi

In PHP, iterating through session data can be achieved through the following steps: 1. Start the session using session_start(). 2. Iterate through foreach loop through all key-value pairs in the $_SESSION array. 3. When processing complex data structures, use is_array() or is_object() functions and use print_r() to output detailed information. 4. When optimizing traversal, paging can be used to avoid processing large amounts of data at one time. This will help you manage and use PHP session data more efficiently in your actual project.

The session realizes user authentication through the server-side state management mechanism. 1) Session creation and generation of unique IDs, 2) IDs are passed through cookies, 3) Server stores and accesses session data through IDs, 4) User authentication and status management are realized, improving application security and user experience.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function

DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software

ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment
