asp图书馆管理系统外文文献

1、外文资ASP3.0&IIS5.0newCharacteristicOne of the most exciting new features in ASP 3.0 and IIS 5.0 is roduction programmable serverside redirection.What this means t, finally, we can transfer control executionofa page tovingtobother外文资ASP3.0&IIS5.0newCharacteristicOne of the most exciting new features in

2、 ASP 3.0 and IIS 5.0 is roduction programmable serverside redirection.What this means t, finally, we can transfer control executionofa page tovingtobotherthentbyusing WellseewhatwemeanbythisTheProblemswithnt-sideASPprogrammers regularly use the Response.Redirect ement to load a different page the t

3、is currently executing. However, many dont t this doesnt cause the server to y load and execute the ge. What it actually does is add HTTPredirectionheadertotheoutputstreambeingsentfromtheWebservertotheThisheaderlookssomethinglikeHTTP/1.1302ObjectLocationThe standard HTTP us his header, 302 Object ls

4、 the tresource they requested has moved. The Location rovides the address of the they want. coursethis ve tobe thereality what ng isfooling the o t page they want can be found at a different location. What is happening t our server executing the page they requested, but ling t page they s moved. Thi

5、s is why we have to execute the Redirect method before we anypagecontenttotheWhenabrowserreceivesthe302ObjectMovedmessageitrespondsbycancelingtherequest and sending a new request for the page he Location value. This works in the same way as when we use a METAHTTP-EQUIV he section of the page theHTTP

6、headershownrisequivalent So the redirection is actually happening on the nt, not on our server. While this generally a problem, it can cause spurious messages to be displayed if there is a proxy server use at the nt end of the connection. The proxy server will ercept the us and may itself generate a

7、 t is sent on to the t made the original request. This whytheubiquitousandannoyingThe object you requested has been moved and can be found here is often displayed on ntwhenand may itself generate a t is sent on to the t made the original request. This whytheubiquitousandannoyingThe object you reques

8、ted has been moved and can be found here is often displayed on ntwhenweuseResponse.Redirect,althoughproperuseofbufferingcanusuallypreventWhen you use Response.Redirect S 4 or r, you should always turn on buffering the top of your ASP page and then call Response.Clear before executing the method. Of

9、course, with page buffering being turned on by default in ASP3.0, this is not such ie. As long as you use Response.Clear before executing the ement,no previously outputwillbesenttotheServer-sideRedirectioninASPInASP3.0andIIS 5.0,we canavoidtheneedtouse nt-sideredirectioninalmostallby taking advantag

10、e of the two new Server object methods: Execute and Transfer. They control to be passed y to age, which can be an ASP script page or any resourcesuchasanHTMLpage,zipfile,orothertypeofThe difference n them t the Execute method calls the age, much like call a subroutine or function in our script code.

11、 When the age or resource has execution or streaming to the nt, control passes back to the ement following the call to Execute he original page, and execution continues from there. When we use Transfermethod, controldoesnotpass backto theoriginal page,andexecution stopsthepageorresourcewetransferred

12、controlWhat makes the two methods even more useful t the current pages context passed to page or resource. This includes the values of all the variables in all rinsicASPobjects,suchasthecollectionsoftheRequest,Responseandobjects,andtheirproperties.TheApplicationcontextisalsotransferred,evenifthepage

13、iswithinadifferentvirtualThe result of all this t the browser t its still receivingthe original page. sno tanything unusual is going on at our server. Its Addressbar still shows the same and (best of all) the Back, Forward and Refresh buttons work normally. When we use nt-redirection,llynHTMLMETAele

14、ment,thisisntusuallythePart of the t is transferred to the ge or resource is any existing e. While we arent going to look at ions in detail until a later chapter, its mentioning here. The current pages context is encapsulated with the ASP ObjectContext which we discussed in Chapter 1. If we need to

15、work with this e. While we arent going to look at ions in detail until a later chapter, its mentioning here. The current pages context is encapsulated with the ASP ObjectContext which we discussed in Chapter 1. If we need to work with this object as part of an ion,wecanuseithe twe transfercontrolWha

16、tareScriptingAn object is basically a way of understanding how the various parts of the systemThe ASP object provides a t we can use to manipulate the he HTTPrequests and responses, and the ASPenvironment as a whole. For we saw how we can find out the values of s sent from the browser by scollection

17、,whichispartof theASPRequestThe scripting languages we use also have an object . However, this is for t the scripting languages provide, as ed to the objects like Request and t are provided directly by the ASP DLL. The scripting objects are provided by Scripting Runtime Library (scrrun.dll), which i

18、s installed with the default Active Scripting providesthreemainobjectsaspartoftheScriptingRuntimeThe Dictionary object provides a useful storage t we can use to store sedandreferencedbytheirnamenbyindex,aswouldbe thecaseina normalFor le, its ideal for storing the name/value t we retrieve from the AS

19、P The FileSystemObject object provides us cs to the underlying file system on server (or on the nt in IE5 when used in conjunction with a l type of page named Hypertext Application or HTA). We can use the FileSystemObject object to iterate through machineslocalandnetworkeddrives,foldersandTheTextStr

20、eamobjectprovidesstofilesstoredondisk,andisusedinconjunctionthe FileSystemObject object. It can read from or write to text (sequential) files. It can only instantiated via the FileSystemObject object, so you might prefer to think of it as a child The ASP Server object is designed to provide the feat

21、ures we need to create these components and applications, t we can use them to extend the capabilities of our scripts. It does this by implementing a l ofthe CreateObject method. Well see thisisrequiredCreatingObjectinVBScriptandInVisualBasic orVisualthese components and applications, t we can use t

22、hem to extend the capabilities of our scripts. It does this by implementing a l ofthe CreateObject method. Well see thisisrequiredCreatingObjectinVBScriptandInVisualBasic orVisualBasicforApplications(VBA),wecancreate of objects avarietyofways.WecanusetheNewkeywordtocreateanewobjectofthetypeDimHoweve

23、r,thissibleinASPwithVBScriptor JScript,because these scriptingdont implement y. We cant declare a variable as being of any specific ype areallVariantsoranequivalenttype(dependingonthescriptinglanguageinternative in Visual Basic and VBAis the use of eric methods. The CreateObject method takes as its

24、argument a or (more usually) a string,andreturnsa newobjecttSetobjNewObject=TheGetObject methodis normallyusedwhenwe haveofa specifictype,andwanttocreate aninstance ofantcanhandlethistype :SetobjExcel=Weso specify the type of t we want as well as a filename, which is useful wehaveseveraltcan tSetobj

25、Excel=GetObject(C:myfilessales.xlw,VBScript supports CreateObject and GetObject. s getObject, which works like VBScript. JScript also implements a t he same way as the CreateObjectmethod, namedActiveXObject.However this isused inconjunction withthe new objNewObject=newWith the exception of the Visual Basic New keyword, which isnt supported in VBScript JScript, we can use all these techniques to create of objects within an ASP However, can doesnt