我的xpath有什么问题？

Question

I have the following xml document:

<Item>
  <DataContainer>
    <ComponentId>12</ComponentId>
    <ChangeTo>undefined</ChangeTo>
    <OperationCode>ADD</OperationCode>
    <ComponentTableName>invFeatureType</ComponentTableName>
    <ComponentColName>invFeatureTypeId</ComponentColName>
    <Type>Feature</Type>
    <PlanFeatureName>Long Distance</PlanFeatureName>
    <ToPlanFeatureName/>
  </DataContainer>
</Item>

When I apply the following xpath to select a specific node :

"/Item/DataContainer[ChangeTo = '12' and Type='Feature']")

I get the following error:

Uncaught DOMException: Failed to execute 'evaluate' on 'Document': The string '/ITEM/DATACONTAINER[CHANGETO = '12' AND TYPE='FEATURE']' is not a valid XPath expression

Any idea ??

Answer 1

Perhaps you just confused ChangeTo with ComponentId ? Given only the document fragment you show, the following XPath expression would retrieve the single DataContainer element:

/Item/DataContainer[ComponentId = '12' and Type='Feature']

It is obvious that you do not show a minimal, complete and verifiable document - which is always a bad idea.

Regarding the error you are getting while evaluating your path expression: If you are actually trying to evaluate a path expression that is all uppercase it will not work. XML and XPath are case-sensitive and the logical and cannot be uppercase in some implementations.

If not, it might be because your XPath library or framework only supports a fraction of the XPath specification. For instance, it might not support predicates (the part between [ and ] ).

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Reacting to a comment:

add // or / at the beginning. – eLRuLL

No, even without // or / a path expression is valid and this will not return the kind of error you are describing.