問題
???
今天在修改程序的一個(gè)BUG時(shí)，竟然發(fā)現(xiàn)selectSingleNode方法不支持contains Xpath函數(shù),感到很奇怪。在網(wǎng)上和MSDN也沒有發(fā)現(xiàn)官方言論表明selectSingleNode不支持contains 函數(shù)。
當(dāng)時(shí)我的情景大概是這樣的：
1、Xml文檔的結(jié)構(gòu)
<?
xml?version="1.0"?
?>
?
<
xsf:xDocumentClass?
xmlns:xsf
="http://schemas.microsoft.com/office/infopath/2003/solutionDefinition"
>
<
xsf:errorCondition?
expressionContext
="T_SUBTITLE/ICHANNELNUM"
>
??
<
xsf:subExpression?
>
Xpath_getSigleNodeValue("T_SUBTITLE/ICHANNELNUM","../ITIMESUSAGE")
<
1
</xsf:subExpression
>
?
??
</
xsf:errorCondition
>
-?
<
xsf:errorCondition?
expressionContext
="T_DESCAUTHORIZE/ITIMESUSAGE"
>
??
<
xsf:subExpression
>
Xpath_getSigleNodeValue("T_DESCAUTHORIZE/ITIMESUSAGE","../ICHANNELNUM")
<
1
</xsf:subExpression
>
?
??
</
xsf:errorCondition
>
</
xsf:xDocumentClass
>
2.我的實(shí)現(xiàn)。
???
我希望通過代碼找到expressionContext不等于T_SUBTITLE/ICHANNELNUM，并且xsf:suExpression中包含字符串"ICHANNELNUM"的節(jié)點(diǎn)。我書寫了以下代碼來實(shí)現(xiàn)：
//
aObjView_Xsf是存儲上述Xml的文檔對象
var
?aObjView_Xsf?
=
new
?ActiveXObject('MSXML2.DOMDocument');
aObjView_Xsf.load(
"
test.xml
"
);
var
?objerrorConditions?
=
?aObjView_Xsf.selectSingleNode(
"
xsf:xDocumentClass/xsf:customValidation/xsf:errorCondition[@expressionContext!='
"
+
strBinding
+
?
"
'?and?contains(xsf:subExpression,'
"
+
fieldName
+
"
')]
"
);
??
這時(shí)IE報(bào)出錯(cuò)誤：contains是未實(shí)現(xiàn)的方法！。這下我就暈了，明明在Xpath的參考手冊，MSDN上都寫著contains是支持的方法。
原因
?
難道真的不支持？
?查閱MSDN我發(fā)現(xiàn)還有以下Xpath函數(shù)：
| Microsoft XML Core Services (MSXML) 4.0 - XPath Reference |
|
String Functions
| concat | Returns the concatenation of the arguments. |
| contains | Returns true if the first argument string contains the second argument string; otherwise returns false. |
| normalize-space | Returns the argument string with the white space stripped. |
| starts-with | Returns true if the first argument string starts with the second argument string; otherwise returns false. |
| string | Converts an object to a string. |
| string-length | Returns the number of characters in the string. |
| substring | Returns the substring of the first argument starting at the position specified in the second argument and the length specified in the third argument. |
| substring-after | Returns the substring of the first argument string that follows the first occurrence of the second argument string in the first argument string. |
| substring-before | Returns the substring of the first argument string that precedes the first occurrence of the second argument string in the first argument string. |
| translate | Returns the first argument string with occurrences of characters in the second argument string replaced by the character at the corresponding position in the third argument string. |
??
難道就只有contains不支持嗎？其他函數(shù)呢？為了證實(shí)我的想法，我嘗試了上述所有函數(shù)，IE都報(bào)出同樣的錯(cuò)誤，原來都不支持！
原來只有4.0版本的支持
???
我發(fā)現(xiàn)這些Xpath函數(shù)的說明在MSXML 4.0 SDK下，難道只有4.0版本支持？于是我把代碼進(jìn)行了修改:
//
aObjView_Xsf是存儲上述Xml的文檔對象
var
?aObjView_Xsf?
=
new
?ActiveXObject('Msxml2.DOMDocument.
4.0
');
aObjView_Xsf.load(
"
test.xml
"
);
var
?objerrorConditions?
=
?aObjView_Xsf.selectSingleNode(
"
xsf:xDocumentClass/xsf:customValidation/xsf:errorCondition[@expressionContext!='
"
+
strBinding
+
?
"
'?and?contains(xsf:subExpression,'
"
+
fieldName
+
"
')]
"
);
?????
運(yùn)行程序，竟然不再拋出contains函數(shù)不支持的錯(cuò)誤了，但是出現(xiàn)另外一個(gè)錯(cuò)誤，xsf是未定義的前綴。對，應(yīng)該是沒有聲明名稱空間。我對代碼再次進(jìn)行了修改：
var
?aObjView_Xsf?
=
new
?ActiveXObject('Msxml2.DOMDocument.
4.0
');
aObjView_Xsf.load(
"
test.xml
"
);
aObjView_Xsf.setProperty(
"
SelectionNamespaces
"
,
"
xmlns:xsf='http://schemas.microsoft.com/office/infopath/2003/solutionDefinition'
"
);
var
?objerrorConditions?
=
?aObjView_Xsf.selectSingleNode(
"
xsf:xDocumentClass/xsf:customValidation/xsf:errorCondition[@expressionContext!='
"
+
strBinding
+
?
"
'?and?contains(xsf:subExpression,'
"
+
fieldName
+
"
')]
"
);
???
運(yùn)行程序，測試通過！于是我下了這樣一個(gè)結(jié)論：只有Msxml2.DOMDocument.4.0以上版本才支持這些Xpath函數(shù)。但是這個(gè)結(jié)論對嗎？我自己也不敢確定。
不只Msxml2.DOMDocument 4.0以上版本支持contains等Xpath函數(shù)
????
我進(jìn)一步的查找了一些資料，都沒有信息表明Msxml2.DOMDocument 2.0不支持這些Xpath函數(shù)。到底Msxml2.DOMDocument 2.0、Msxml2.DOMDocument 3.0為什么支持類似等于、不等于、大于這樣的操作符，而無法識別contains這樣的函數(shù)呢？直到我發(fā)現(xiàn)了這個(gè)方法：setProperty("SelectionLanguage", "XPath")。這時(shí)我恍然大悟，原來4.0以下版本的Msxml2.DOMDocument默認(rèn)用類似正則匹配的方法來進(jìn)行節(jié)點(diǎn)選取的，而4.0及以上版本默認(rèn)采用Xpath作為默認(rèn)的選擇語言。
??? 我采用Msxml2.DOMDocument 2.0，將代碼做以下修改也是可以正常運(yùn)行的：
//
aObjView_Xsf是存儲上述Xml的文檔對象
var
?aObjView_Xsf?
=
new
?ActiveXObject('MSXML2.DOMDocument');
aObjView_Xsf.setProperty(
"
SelectionLanguage
"
,?
"
XPath
"
);
aObjView_Xsf.setProperty(
"
SelectionNamespaces
"
,
"
xmlns:xsf='http://schemas.microsoft.com/office/infopath/2003/solutionDefinition'
"
);
aObjView_Xsf.load(
"
test.xml
"
);
var
?objerrorConditions?
=
?aObjView_Xsf.selectSingleNode(
"
xsf:xDocumentClass/xsf:customValidation/xsf:errorCondition[@expressionContext!='
"
+
strBinding
+
?
"
'?and?contains(xsf:subExpression,'
"
+
fieldName
+
"
')]
"
);
?
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