javascript asp教程第八课--request对象
2018-09-06 11:26
Request Object:
Request has five (5) Collections, one (1) Property, and one (1) Method. Youll use the Collections far more than the property or the method.
Request Collections:
Below is a table of the Request Collections and descriptions of how they are used.
Request Collections ClientCertificate Request.ClientCertificate(Key[Field])
Client security info for SSL encryption Cookies
Holds cookie value stored on the client Form Request.Form(formName)
Holds value sent via HTML Form QueryString Request.QueryString(keyName)
Name/Value pair appended to the end of the URL ServerVariables Request.ServerVariables(variableName)
Hold values sent in the HTTP Headers
ClientCertificate:
Request.ClientCertificate is used with S.S.L. (Secure Sockets Layer). It is beyond the scope of this web site.
Cookies:
We will learn Request.Cookies and Response.Cookies together in Lesson 08. Please be patient.
Form:
Request.Form is probably the workhorse of the Request Collections. The first script is a repeat from Lesson 03.
<%@LANGUAGE=JavaScript%> <% //No ASP Here, just a regular HTML Page %> <HTML> <STRONG>Type something into the text box and submit it.</STRONG> <FORM ACTION=script08a.asp METHOD=Post> <INPUT TYPE=Text NAME=WebPageVariable><BR> <STRONG>How Much Money do you make each month?</STRONG><BR> <SELECT NAME=monthlySalary> <OPTION>Under $5,000,000</OPTION> <OPTION>Above $5,000,000</OPTION> <OPTION>Nobodys darn business.</OPTION> </SELECT><BR> <INPUT TYPE=Submit VALUE=Submit> </FORM> </HTML>
Click Hereto run script08.asp in a new window. It posts information to script08a.asp which is found below. In turn, script08a.asp posts information to script08b.asp which is also found below.
<%@LANGUAGE=JavaScript%> <% var WebPageVariable = new String( Request.Form(WebPageVariable) ) WebPageVariable = WebPageVariable.toUpperCase(); var monthlySalary = new String( Request.Form(monthlySalary) ) monthlySalary = monthlySalary.toLowerCase(); %> <HTML> The Web Page Variable you typed is: <%=WebPageVariable%> <BR> The monthly salary you listed is: <%=monthlySalary%> <BR> <FORM ACTION=script08b.asp METHOD=Get> <INPUT TYPE=hidden VALUE=<%=monthlySalary%> NAME=QueryVariable> <STRONG>Click the button to see Query Strings</STRONG><BR> <INPUT TYPE=submit VALUE=Submit> </FORM> </HTML>
Well be using Request.Form when we Post an HTML form to the server. Notice that the NAME attribute in the HTML form corresponds to the name in Request.Form(name). To be more specific, <INPUT TYPE=Text NAME=WebPageVariable> corresponds with Request.Form(WebPageVariable). We already talked about the need for the new String( ) constructor back in Lesson 03.
QueryString:
Well be using Request.QueryString when we use an HTML form to Get a page from the server. Request.QueryString() is very similar to Request.Form(). Take a look at script08b.asp which I printed below.
<%@LANGUAGE=JavaScript%> <% var QueryVariable = new String( Request.QueryString(QueryVariable) ) %> <HTML> The QueryString Value is: <%=QueryVariable%> <BR> <% if (QueryVariable != Lesson 08s new Query!) { QueryVariable=Lesson 08s new Query! QueryVariable=escape(QueryVariable) %> <A HREF=script08b.asp?QueryVariable=<%=QueryVariable%>>Click Here</A> for the link to <I>script08b.asp?QueryVariable=<%=QueryVariable%></I> <% } //closing bracket for if statement. %> </HTML>
If you havent already,Click Hereto run script08.asp in a new window. Cycle through all the forms and links, and then come back.
You can use Request.QueryString in two different ways. You can either use an HTML form to Get a page from the server, which will generate a query string. Or you can manually build a query string and add it to the backside of a link. Well dissect script08b.asp from top to bottom.
var QueryVariable = new String( Request.QueryString(QueryVariable) )
The line above in script08b.asp corresponds to the line below from script08a.asp
<INPUT TYPE=hidden VALUE=<%=monthlySalary%> NAME=QueryVariable>
The NAME=someName in the HTML form becomes the Request.QueryString(someName) on the next page.
About half way into script08b.asp are the lines I reprinted below.
<% if (QueryVariable != Lesson 08s new Query!) { QueryVariable=Lesson 08s new Query! QueryVariable=escape(QueryVariable) %>
Weve already converted Request.QueryString() into a JavaScript string at the top of the script. So, now we can do a string comparison.
If the QueryVariable hasnt already been set equal to Lesson 08s new Query! then we do that. Then we use the escape( ) method to convert white space and special characters into Unicode. (URLs should contain neither whitespace, nor most special characters.)
In lesson 14 well see a better way to encode URLs. When we study the Server Object, well see Server.URLEncode(). But for now, just know that escape() works.
You can have more than one QueryString on each page. If you lose count of your QueryStrings, then you use to tell you the number.
The Request Shortcut:
Request.Form() and Request.QueryString() share a shortcut. Request.Form(WebPageVariable) can be abbreviated as Request(WebPageVariable) and Request.QueryString(QueryVariable) can be abbreviated as Request(QueryVariable).
ServerVariables:
Server Variables represent the HTTP Headers sent to the server by the client. I wont demonstrate them all, because there are too many.
<%@LANGUAGE=JavaScript%> <HTML> <TABLE BORDER=1> <TR><TD>ALL_RAW</TD> <TD><%=Request.ServerVariables(ALL_RAW)%></TD></TR> <TR><TD>REMOTE_ADDR</TD> <TD><%=Request.ServerVariables(REMOTE_ADDR)%></TD></TR> <TR><TD>HTTP_USER_AGENT</TD> <TD><%=Request.ServerVariables(HTTP_USER_AGENT)%></TD></TR> <TR><TD>URL</TD> <TD><%=Request.ServerVariables(URL)%></TD></TR> </TABLE> </HTML>
Click Hereto run the script in a new window.
Demonstrated above are four (4) server variables. There are (give or take) about 50 server variables available. You can look up the full list of server variables for yourself on the internet.
Misc. Notes:
Request.BinaryRead() is the lone method and TotalBytes is the lone property. Request.BinaryRead(Request.TotalBytes) retrieves data from an HTML form using POST. You must supply the TotalBytes as an argument. It stores the data into an array. BinaryRead cannot be used at the same time as Request.Form().
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