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1、Silberschatz, Korth and Sudarshan9.1Database System Concepts - 6th EditionChapter 9: Application Design and Development Silberschatz, Korth and Sudarshan9.2Database System Concepts - 6th EditionChapter 9: Application Design and Development Chapter 9: Application Design and Development nApplication P
2、rograms and User InterfacesnWeb FundamentalsnServlets and JSPnApplication ArchitecturesnRapid Application DevelopmentnApplication PerformancenApplication SecuritynEncryption and Its ApplicationsSilberschatz, Korth and Sudarshan9.3Database System Concepts - 6th EditionApplication Programs and User In
3、terfacesApplication Programs and User InterfacesnMost database users do not use a query language like SQLnAn application program acts as the intermediary between users and the databaselApplications split into4front-end4middle layer4backendnFront-end: user interfacelFormslGraphical user interfaceslMa
4、ny interfaces are Web-basedSilberschatz, Korth and Sudarshan9.4Database System Concepts - 6th EditionApplication Architecture EvolutionnThree distinct eras of application architecturelmainframe (1960s and 70s)lpersonal computer era (1980s)lWe era (1990s onwards)Silberschatz, Korth and Sudarshan9.5Da
5、tabase System Concepts - 6th EditionWeb InterfacenWeb browsers have become the de-facto standard user interface to databaseslEnable large numbers of users to access databases from anywherelAvoid the need for downloading/installing specialized code, while providing a good graphical user interface4Jav
6、ascript, Flash and other scripting languages run in browser, but are downloaded transparentlylExamples: banks, airline and rental car reservations, university course registration and grading, an so on.Silberschatz, Korth and Sudarshan9.6Database System Concepts - 6th EditionThe World Wide WebnThe We
7、b is a distributed information system based on hypertext.nMost Web documents are hypertext documents formatted via the HyperText Markup Language (HTML)nHTML documents containltext along with font specifications, and other formatting instructionslhypertext links to other documents, which can be assoc
8、iated with regions of the text.lforms, enabling users to enter data which can then be sent back to the Web serverSilberschatz, Korth and Sudarshan9.7Database System Concepts - 6th EditionUniform Resources LocatorsnIn the Web, functionality of pointers is provided by Uniform Resource Locators (URLs).
9、nURL example: http:/www.acm.org/sigmod lThe first part indicates how the document is to be accessed4“http” indicates that the document is to be accessed using the Hyper Text Transfer Protocol.lThe second part gives the unique name of a machine on the Internet.lThe rest of the URL identifies the docu
10、ment within the machine.nThe local identification can be:4The path name of a file on the machine, or4An identifier (path name) of a program, plus arguments to be passed to the programE.g., http:/ Korth and Sudarshan9.8Database System Concepts - 6th EditionHTML and HTTPnHTML provides formatting, hype
11、rtext link, and image display featureslincluding tables, stylesheets (to alter default formatting), etc.nHTML also provides input features4Select from a set of optionsPop-up menus, radio buttons, check lists4Enter valuesText boxeslFilled in input sent back to the server, to be acted upon by an execu
12、table at the servernHyperText Transfer Protocol (HTTP) used for communication with the Web serverSilberschatz, Korth and Sudarshan9.9Database System Concepts - 6th EditionSample HTML Source Text ID Name Department 00128 Zhang Comp. Sci. . Search for: Student Instructor Name: Silberschatz, Korth and
13、Sudarshan9.10Database System Concepts - 6th EditionDisplay of Sample HTML SourceSilberschatz, Korth and Sudarshan9.11Database System Concepts - 6th EditionWeb ServersnA Web server can easily serve as a front end to a variety of information services.nThe document name in a URL may identify an executa
14、ble program, that, when run, generates a HTML document.lWhen an HTTP server receives a request for such a document, it executes the program, and sends back the HTML document that is generated.lThe Web client can pass extra arguments with the name of the document.nTo install a new service on the Web,
15、 one simply needs to create and install an executable that provides that service.lThe Web browser provides a graphical user interface to the information service.nCommon Gateway Interface (CGI): a standard interface between web and application serverSilberschatz, Korth and Sudarshan9.12Database Syste
16、m Concepts - 6th EditionThree-Layer Web ArchitectureSilberschatz, Korth and Sudarshan9.13Database System Concepts - 6th EditionTwo-Layer Web ArchitecturenMultiple levels of indirection have overheadsAlternative: two-layer architectureSilberschatz, Korth and Sudarshan9.14Database System Concepts - 6th EditionHTTP and SessionsnThe HTTP protocol is connectionlesslThat is, once the server replies to a request, the server closes the connection with the client, and forgets all about the requestlIn con
