<?php /** (1)外观模式(Facade)也叫门面模式,为子系统中的一组接口提供一个一致的界面,此模式定义了一个高层接口,这个接口使得这一子系统更加容易使用。 为一些复杂的子系统提供一组接口 (2)主要角色门面(Facade)角色? 此角色将被客户端调用? 知道哪些子系统负责处理请求? 将用户的请求指派给适当的子系统子系统(subsystem)角色? 实现子系统的功能? 处理由Facade对象指派的任务? 没有Facade的相关信息,可以被客户端直接调用? 可以同时有一个或多个子系统,每个子系统都不是一个单独的类,而一个类的集合。每个子系统都可以被客户端直接调用,或者被门面角色调(3)使用情况 : 首先,在设计初期阶段,应该要有意识将不同的两个层分离,比如经典的三层架构,就需要考虑在数据访问层和业务逻辑层、业务逻辑层和表示层的层与层之间建立外观Facade,这样可以为复杂的子系统提供一个简单的接口,使得耦合度大大降低。 其次,在开发阶段,子系统往往因为不断的重构演化而变得越来越复杂,大多数的模式使用时也都会产生很多很小的类,这本是好事,但也给外部调用它们的用户程序带来了使用上的困难,增加外观Facade可以提供一个简单的接口,减少它们之间的依赖。 第三,在维护一个遗留的大型系统时,可能这个系统已经非常难以维护和扩展了,但因为它包含非常重要的功能,新的需求开发必须要依赖于它。此时,用外观模式Facade也是非常合适的。你可以为新系统开发一个外观Facade类,来提供设计粗糙或高度复杂的遗留代码的比较清晰的简单接口,让新系统与Facade对象交互,Facade与遗留代码交互所有复杂的工作。”(4) 具体事例 比如我关机,整个过程包括关闭显示器,关闭pc机器,关闭电源 ,关机的按钮就是门面的角色,其他为子系统*/// 门面抽象接口 interface Facade{ public function turnOn() ; public function turnOff() ;}// (1) 关闭显示器class PcLight { public function turnOn() {} public function turnOff() { echo 'turn off PcLight <br>' ; } }//(2) pc 机器class Pcmachine { public function turnOn() {} public function turnOff() { echo 'turn off PcMathion <br>' ; }}// (3) 关闭电源class Power { public function turnOn() {} public function turnOff() { echo 'turn off Power <br>' ; }}// 关机的门面角色 class PcFacade implements Facade{ private $PcLight ; private $Pcmachine ; private $Power ; public function __construct(){ $this->PcLight = new PcLight(); $this->Pcmachine = new Pcmachine(); $this->Power = new Power(); } // 门面角色的应用 public function turnOff() { $this->PcLight ->turnOff(); $this->Pcmachine ->turnOff(); $this->Power ->turnOff(); } public function turnOn() {} }// 应用$button = new PcFacade(); $button ->turnOff(); /* 其实门面模式就是把几个子系统(实例或者类.统一一个统一的接口进行执行,客户端不用关注子系统,只用门面即可 )

Load balancing affects session management, but can be resolved with session replication, session stickiness, and centralized session storage. 1. Session Replication Copy session data between servers. 2. Session stickiness directs user requests to the same server. 3. Centralized session storage uses independent servers such as Redis to store session data to ensure data sharing.

Sessionlockingisatechniqueusedtoensureauser'ssessionremainsexclusivetooneuseratatime.Itiscrucialforpreventingdatacorruptionandsecuritybreachesinmulti-userapplications.Sessionlockingisimplementedusingserver-sidelockingmechanisms,suchasReentrantLockinJ

Alternatives to PHP sessions include Cookies, Token-based Authentication, Database-based Sessions, and Redis/Memcached. 1.Cookies manage sessions by storing data on the client, which is simple but low in security. 2.Token-based Authentication uses tokens to verify users, which is highly secure but requires additional logic. 3.Database-basedSessions stores data in the database, which has good scalability but may affect performance. 4. Redis/Memcached uses distributed cache to improve performance and scalability, but requires additional matching

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