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简单的说使用Cache基本原理是，把经常需要且获得代价昂贵的数据在内存中持续保存一定时间，以供这些数据可以被直接地全局地访问。例如，有一些数据需要从数据库多个表中查询获得，且几乎每个页面都要调用这些数据。
以下代码程序实现ASP定时刷新Cache，也就是说给Application中储存的设一个过期时间。
以下为引用的内容：
default.asp
<%@Language=VBScript%>
<%Option Explicit%>
<%Response.Buffer=True%>
<!--#include file = "conn.asp"-->
<!--#include file = "GetCache.asp"-->
<HTML>
<HEAD>
<TITLE>ASP Cache演示</TITLE>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=gb2312">
</HEAD>
<BODY>
<h4>每隔10秒刷新Cache：</h4>
<%
response.Flush
GetHTMLStream
response.Write
HTMLStream
%>
</body>
</html> |
以下为引用的内容：
getcache.asp
<%
Const CACHE_DEFAULT_INTERVAL = 30 '每隔30秒刷新一次cache
Dim HTMLStream
Dim IsExpires
IsExpires = CacheExpires
Function CacheExpires
Dim strLastupdate
Dim result strLastupdate = Application("Lastupdate")
If (strLastupdate = "") Or (CACHE_DEFAULT_INTERVAL < DateDiff("s", strLastupdate, Now)) Then
result = true
SetLastupdateTime
Else
result = false
End If
CacheExpires = result
End Function
Sub SetLastupdateTime
Application.Lock
Application("Lastupdate") = CStr(now())
Application.UnLock
End Sub
Sub GetHTMLStream
If IsExpires Then
updateHTMLStream
End If
HTMLStream=Application("CACHE_HTMLStream")
End Sub |
以下为引用的内容：
Sub updateHTMLStream
dim d
d = FetchHTMLStream
Application.Lock
Application("CACHE_HTMLStream") = d
Application.UnLock
End Sub
Function FetchHTMLStream
Dim rs ,strSQL, strHTML
Set rs = createObject("ADODB.Recordset")
strSQL = "select categoryID , categoryname from categories"
rs.Open strSQL, strConn,adOpenForwardOnly,adLockReadOnly
strHTML = strHTML & "<select name=""slt_search"">"
while (not rs.EOF)
strHTML = strHTML & "<option>"
strHTML = strHTML & rs.Fields("categoryname")
strHTML = strHTML & "</option>" rs.MoveNext
wend
strHTML = strHTML & "</select>"
rs.Close
Set rs = Nothing
FetchHTMLStream = strHTML
End Function
%> |
以下为引用的内容：
conn.asp
<!--METADATA NAME="Microsoft ActiveX Data Objects 2.5 Library" TYPE="TypeLib" UUID="{00000205-0000-0010-8000-00AA006D2EA4}"-->
<%
dim strConn
strConn = "Provider=SQLOLEDB.1;Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=Northwind"
%> |
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