基于bs模式的教務管理系統的設計與實現畢業設計外文翻譯-預覽頁

　

【正文】 服務器結構隨著企業應用的擴展，最近又出現了一種新的多層體系結構，它把客戶端應用分為兩部分：客戶應用和服務器應用。如下圖所示：這種結構解決了傳統Client/Server的可擴展問題，既減少了客戶端業務邏輯，又降低了客戶端對硬件的要求。本質上，Browser/Server也是一種Client/Server結構，它是一種由傳統的二層Client/Server結構發展而來的三層Client/Server結構在Web上應用的特例。在表示層中包含系統的顯示邏輯，位于客戶端。它的任務是接受用戶的請求，首先需要執行相應的擴展應用程序與數據庫進行連接，通過SQL等方式向數據庫服務器提出數據處理申請，而后等數據庫服務器將數據處理的結果提交給Web服務器，再由Web服務器傳送回客戶端。仔細分析不難看出，三層的Browser/Server體系結構是把二層Client/Server結構的事務處理邏輯模塊從客戶機的任務中分離出來，由單獨組成的一層來負擔其任務，這樣客戶機的壓力大大減輕了，把負荷均衡地分配給了Web服務器，于是由原來的兩層的Client/server結構轉變成三層的Browser/Server結構。這種三層結構層與層之間相互獨立，任何一層的改變不影響其它層的功能。較低的開發和維護成本：Client/Server的應用必須開發出專用的客戶端軟件，無論是安裝、配置還是升級都需要在所有的客戶機上實施，極大地浪費了人力和物力。客戶端消腫：Client/Server的客戶端具有顯示與處理數據的功能，對客戶端的要求很高，是一個“胖”客戶機。保障系統的安全性：在Client/Server系統中由于客戶機直接與數據庫服務器進行連接，用戶可以很輕易的改變服務器上的數據，無法保證系統的安全性。什么是C/S和B/S：要想對“C/S”和“B/S”技術發展變化有所了解，首先必須搞清楚三個問題。目前大多數應用軟件系統都是Client/Server形式的兩層結構，由于現在的軟件應用系統正在向分布式的Web應用發展，Web和Client/Server 應用都可以進行同樣的業務處理，應用不同的模塊共享邏輯組件；因此，內部的和外部的用戶都可以訪問新的和現有的應用系統，通過現有應用系統中的邏輯可以擴展出新的應用系統。而且代價高， 效率低。它是隨著Internet技術的興起，對C/S結構的一種變化或者改進的結構。它是一次性到位的開發，能實現不同的人員，從不同的地點，以不同的接入方式(比如LAN, WAN, Internet/Intranet等)訪問和操作共同的數據庫；它能有效地保護數據平臺和管理訪問權限，服務器數據庫也很安全 。管理軟件技術的主流技術與管理思想一樣，也經歷了三個發展時期。目前，這兩項技術以被世界各國所掌握，國內公司以C/S和B/S技術開發出產品也很多。運行數據庫服務器程序的機器，也稱為應用服務器。所有這些，對于工作在前臺程序上的最終用戶，是“透明”的，他們無須過問(通常也無法干涉)背后的過程，就可以完成自己的一切工作。首先，采用C/S架構，要選擇適當的數據庫平臺來實現數據庫數據的真正“統一”，使分布于兩地的數據同步完全交由數據庫系統去管理，但邏輯上兩地的操作者要直接訪問同一個數據庫才能有效實現，有這樣一些問題，如果需要建立“實時”的數據同步，就必須在兩地間建立實時的通訊連接，保持兩地的數據庫服務器在線運行，網絡管理工作人員既要對服務器維護管理，又要對客戶端維護和管理，這需要高昂的投資和復雜的技術支持，維護成本很高，維護任務量大。目前，軟件系統的改進和升級越來越頻繁，B/S架構的產品明顯體現著更為方便的特性。今后，軟件升級和維護會越來越容易，而使用起來會越來越簡單，這對用戶人力、物力、時間、費用的節省是顯而易見的，驚人的。 現在的趨勢是凡使用B/S架構的應用管理軟件，只需安裝在Linux服務器上即可，而且安全性高。由于B/S架構管理軟件只安裝在服務器端(Server)上，網絡管理人員只需要管理服務器就行了，用戶界面主要事務邏輯在服務器(Server)端完全通過WWW瀏覽器實現，極少部分事務邏輯在前端(Browser)實現，所有的客戶端只有瀏覽器，網絡管理人員只需要做硬件維護。 Another part faces every user , is realized by client puter, also namely, client puter is usual to carry out proscenium function , realizes manmachine interaction through user interface , or is the application program of specific conducted user. And server usually carries out the function of backstage supporter , manages the outside request concerning seting up, accepting and replying user that shared. For a puter, it can have double function , is being certain and momentary to carve to act as server , and again bees client puter in another time. Customer / server type puter divide into two kinds, one side who offers service is called as server , asks one side of service to be called as customer. To be able to offer service, server one side must have certain hardware and corresponding server software。s task is the request concerning accepting user , need to be first conducted and corresponding to expand application program and database to carry out connection , passes through the waies such as SQL to database server to put forward data handling to apply for, then etc. database server the result of handling data submit to Web server, deliver again by Web server to return customer end. The number of plies of 3th according to layer: Database server. In data layer contain systematic data handling logic, locate in database server end. It39。s management software statistics of law case is typical C / S architecture management software. (2) What is the structure of B/S. B/S ( Browser/Server ) structure browser and server structure. It is along with the technology of Internet spring up , it is for the structure of improvement or a kind of change of the structure of C/S. Under this kind of structure, user working interface is to realize through WWW browser, lose the logic of general affairs very much in front( Browser) realization, but the major logic of general affairs in server end( Server) realization, form the threelayer claimed 3tier structure. So, have simplified customer end puter load greatly , have alleviated system to defend workload and the cost with upgrading , have reduced the overall cost of user ( TCO ). With present technology see , local area network the network application that establishes the structure of B/S , and under the pattern of Internet/Intranet, database application is easy to hold relatively , cost also is lower. It is that oneness goes to the development of position , can realize different people, never same place, with difference receive the way of entering ( for example LAN, WAN, Internet/Intranet etc.) visit and operate mon database。 If need differently only, net server connection specially , realize longrange maintenance and upgrading and share. So client puter more and more thin , and server more and more fat is the direction of main stream of future informative development. In the future, software upgrading and maintenance will be more and more easy , and use can more and more simple, this is for user manpower , material resources, time and cost save is obvious , it is astonishing. Therefore defend and escalate revolutionary way is the client puter it is thin , is fat server. (2) Cost reduction, it is more to select. All know windows in the puter of top of a table on nearly one Tong world, browser has bee standard disposition, but on server operating system, windows is in absolute dominance position not. Current tendency is the application management software that uses the configuration of B/S all , need to install only in Linux server on , and safety is high. The so server option of operating system is many, no matter choosing those operating system, can let the most of ones use windows in order to the puter of top of a table of operating system does not get influence, this for make most popular free Linux operating system develop fast, Linux except operating system is free besides, it is also free to link database, this kind of option is very pupular. Say, many persons on daily, Sina website nets , so long as having installed browser for can , and what need not know the server of Sina website to use is that what operating system, and in fact the most of websites do not use windows