|
ASP中查錯之實例
有這樣一個程序，是對Application集合中的元素進行活動的添加與刪除，程序如下：
<%@ LANGUAGE=VBSCRIPT %>
<HTML>
<HEAD>
<TITLE>The Application Object</TITLE>
<STYLE TYPE="text/css">
BODY {font-family:Tahoma,Arial,sans-serif; font-size:10pt}
INPUT {font-family:Tahoma,Arial,sans-serif; font-size:9pt}
.heading {font-family:Tahoma,Arial,sans-serif; font-size:14pt; font-weight:bold}
.subhead {font-family:Tahoma,Arial,sans-serif; font-size:12pt; font-weight:bold; padding-bottom:5px}
.cite {font-family:Tahoma,Arial,sans-serif; font-size:8pt}
</STYLE>
</HEAD>
<BODY BGCOLOR="#FFFFFF">
<SPAN CLASS="heading">The ASP Application Object</SPAN><HR>
<!--------------------------------------------------------------------------->
<% 'look for a command sent from the FORM section buttons
If Len(Request.Form("cmdAdd")) Then ' 利用是否長度為0來判斷
strVarName = Request.Form("txtVarName")
strVarValue = Request.Form("txtVarValue")
Application.Lock
Application(strVarName) = strVarValue ' 此處報錯
Application.Unlock
End If
If Len(Request.Form("cmdRemoveThis")) Then
strToRemove = Request.Form("lstRemove")
Application.Lock
Application.Contents.Remove(strToRemove)
Application.Unlock
End If
If Len(Request.Form("cmdRemoveAll")) Then
Application.Lock
Application.Contents.RemoveAll
Application.Unlock
End If
%>
<P><DIV CLASS="subhead">The Application.Contents Collection</DIV>
<%
For Each objItem in Application.Contents
If IsObject(Application.Contents(objItem)) Then
Response.Write "Object reference: '" & objItem & "'<BR>"
ElseIf IsArray(Application.Contents(objItem)) Then
Response.Write "Array: '" & objItem & "' contents are:<BR>"
varArray = Application.Contents(objItem)
'note: the following only works with a one-dimensional array
For intLoop = 0 To UBound(varArray)
Response.Write " Index(" & intLoop & ") = " & varArray(intLoop) & "<BR>"
Next
Else
Response.Write "Variable: '" & objItem & "' = " _
& Application.Contents(objItem) & "<BR>"
End If
Next
%>
<P><DIV CLASS="subhead">The Application.StaticObjects Collection</DIV>
<%
For Each objItem in Application.StaticObjects
If IsObject(Application.StaticObjects(objItem)) Then
Response.Write "<OBJECT> element: ID='" & objItem & "'<BR>"
End if
Next
%>
<!-- collect values to execute Application methods with -->
<FORM ACTION="<% = Request.ServerVariables("SCRIPT_NAME") %>" METHOD="POST"> ' 利用Request.ServerVariables("SCRIPT_NAME")將表單提交給自身
<P><DIV CLASS="subhead">Add a value to the Application Object</DIV>
<INPUT TYPE="SUBMIT" NAME="cmdAdd" VALUE=" ">
Application("
<INPUT TYPE="TEXT" NAME="txtVarName" SIZE="15" VALUE="My_New_Value">
") = "
<INPUT TYPE="TEXT" NAME="txtVarValue" SIZE="20" VALUE="Testing, testing ...">
"<P>
<P><DIV CLASS="subhead">Remove a value from the Application Object</DIV>
<INPUT TYPE="SUBMIT" NAME="cmdRemoveThis" VALUE=" ">
Application.Contents.Remove("
<SELECT NAME="lstRemove" SIZE="1">
<%
For Each objItem in Application.Contents
Response.Write "<OPTION>" & objItem & "</OPTION>"
Next
%>
</SELECT>")<BR>
<INPUT TYPE="SUBMIT" NAME="cmdRemoveAll" VALUE=" ">
Application.Contents.RemoveAll
</FORM>
<P><DIV CLASS="subhead">Other Application Methods</DIV>
Application.Lock<BR>
Application.Unlock<P>
<!--------------------------------------------------------------------------->
<HR><SPAN CLASS="cite">©1999 <A CLASS="cite" >Wrox Press</A> -
<A CLASS="cite" >Professional ASP 3.0</A> (ISBN: 1-861002-61-0)</SPAN>
</BODY>
</HTML>
該程序的報錯信息如下：
技術(shù)信息（適用于支持人員）
· 錯誤類型：
應用程序?qū)ο? ASP 0102 (0x80004005)
函數(shù)需要字符串輸入。
/Chapter03/application/show_application.asp, 第 22 行
· 瀏覽器類型：
Mozilla/4.0 (compatible; MSIE 5.5; Windows NT 5.0; COM+ 1.0.2204)
· 頁：
POST 98 bytes to /Chapter03/application/show_application.asp
· POST 數(shù)據(jù):
cmdAdd=%A0%A0%
· A0&txtVarName=My_New_Value&txtVarValue=Testing%2C+testing+...&lstRemove=My_New_Value
· 時間：
2001年2月16日, 9:42:28
賴皮曾指出Application(strVarName) = strVarValue應為Application("strVarName") = strVarValue，雖然這樣做可以通過，但于程序的原意不符，程序要做的是通過Request.Form集合來獲取。而且既然是wrox的例題，應該不太會出什么問題。
步驟1：在報錯的上一行加入Response.Write("AAA")，目的是檢驗If … Then語句是否起作用，結(jié)果發(fā)現(xiàn)If … Then語句起作用的。
步驟2：將出錯的一句注釋掉，并將Response.Write("AAA")改為
Response.Write "strVarName = " & strVarName & "<BR>"
Response.Write "strVarValue = " & strVarValue
結(jié)果為：strVarName =
strVarValue = Testing, testing ...
為什么會strVarName沒有值，而strVarValue卻有值呢？同樣都是Text輸入框，卻會有不同的結(jié)果。反復觀察后，發(fā)現(xiàn)Submit的值為" "，即為三個空格，是否會由空格引起的呢？
步驟3：遍歷Request.Form集合，將兩句Response.Write跟蹤變量語句改為
For Each strName in Request.Form
Response.Write strName & " = " & Request.Form(strName) & "<BR>"
Next
結(jié)果為：
cmdAdd = 牋?txtVarName=My_New_Value
txtVarValue = Testing, testing ...
lstRemove = My_New_Value
果然是由于空格造成的亂碼，可這源程序是例題，不應該有錯呀。想到wrox用的是英文Windows 2000，我用的是中文，那么應該是由雙字節(jié)的關(guān)系，就應該修改CODEPAGE。
而我忘記了中文CODEPAGE的代碼，在ASP 3.0高級編程中，曾寫過日文的CODEPAGE為932，日文也應該是雙字節(jié)的。所以將源程序的第一行改為：
<%@ LANGUAGE="VBSCRIPT" CODEPAGE="932" %>
程序通過！
這里想向初學者提出的是，注意Response.Write和For … Each遍歷來跟蹤變量，找出錯誤的原因，注意雙字節(jié)對程序的影響，還有本文中If … Then中的判斷條件的方法。
|
