XPath Check Node is Blank

问题

Using XPath, how to check if the node or tag value is blank?

Given the Sample XML:

Questions (Need XPath expression for the following):
1. how will I check if ExceptionMessage1 is blank.
2. how will I check if ExceptionMessage2 @nil == true?
3. how about if there will be ExceptionMessage3, it can either be:
a. Contains exception message
b. No message, with @nil="true" (Combined ExceptionMessage1 & ExceptionMessage2 behaviors)

<Envelope>
   <Body>
      <SellResponse>
         <SellResult>
            <ExceptionMessage1>JourneyManager.SellJourney(segment): Segment already booked under different class of service</ExceptionMessage1>
            <ExceptionMessage2 nil="true"/>
            <NSProcessTime>0</NSProcessTime>
            <ProcessTime>0</ProcessTime>
            <Booking nil="true"/>
            <Success nil="true"/>
            <Warning nil="true"/>
            <Error nil="true"/>
            <OtherServiceInformations nil="true"/>
         </SellResult>
      </SellResponse>
   </Body>
</Envelope>

TIA

回答1:

"check if ExceptionMessage1 is blank"

The following should return true if ExceptionMessage1 has child node (not blank) and return false otherwise :

not(//ExceptionMessage1/node())

"check if ExceptionMessage2 @nil == true"

This is straightforward, I think :

boolean(//ExceptionMessage2/@nil = 'true')

"With ExceptionMessage3, I want to check if it is not blank or nil=true"

The following XPath returns true, if there is ExceptionMessage3 that is not blank or has attribute nil equals 'true' :

boolean(//ExceptionMessage3[node() or @nil='true'])

You might be able to omit boolean() call if the context explicitly expects a boolean value. The conversion will be automatic in that case.

回答2:

//ExceptionMessage1/text() = '' - it will check if the content of the element is an empty string - just google any Xpath tutorial for more examples or if you need the inverse.
//ExceptionMessage2/@nil = 'true'
Just use or to combine the two Xpaths above

回答3:

I guess somebody might encounter similar issues like this, so I just post the solutions I gather from Lech & har07, thanks guys.

I use the online XPath Tester (http://xpatheval.apphb.com)

how will I check if ExceptionMessage1 is blank or empty string.
//ExceptionMessage1/text() = ''
http://xpatheval.apphb.com/KHg6afoO2

empty(//ExceptionMessage1/text())
http://xpatheval.apphb.com/lZHxs8BO6
how will I check if ExceptionMessage2 @nil == true?
//ExceptionMessage2/@nil = 'true'
http://xpatheval.apphb.com/8Tf7Kf8yx

boolean(//ExceptionMessage2/@nil = 'true')
http://xpatheval.apphb.com/_KcXIH9fU

If the attribute nil's value is false, it will also return false

how about if there will be ExceptionMessage3, it can either be:
a. Contains exception message
b. No message, with @nil="true" (Combined ExceptionMessage1 & ExceptionMessage2 behaviors)

<Envelope>    
   <Body>    
       <SellResponse>    
           <SellResult>    
               <ExceptionMessage1>JourneyManager.SellJourney(segment): Segment already booked under different class of service</ExceptionMessage1>    
               <ExceptionMessage2 nil="true"/>    
               <ExceptionMessage3 nil="false">JourneyManager.SellJourney(segment): No funds to proceed with the transaction</ExceptionMessage3>    
               <NSProcessTime>0</NSProcessTime>    
               <ProcessTime>0</ProcessTime>    
               <Booking nil="true"/>    
               <Success nil="true"/>    
               <Warning nil="true"/>    
               <Error nil="true"/>    
               <OtherServiceInformations nil="true"/>    
           </SellResult>    
       </SellResponse>    
   </Body>    
</Envelope>

Check if empty or nil="true"
empty(//ExceptionMessage3/text()) or //ExceptionMessage3/@nil = "true"
http://xpatheval.apphb.com/qp2ejO_y1
Check if not empty or nil="false"
not(empty(//ExceptionMessage3/text())) or //ExceptionMessage3/@nil = "false"
http://xpatheval.apphb.com/v1b72d6ZK

Thanks Lech Rzedzicki & har07 for the help.

来源：https://stackoverflow.com/questions/37158797/xpath-check-node-is-blank

标签

xml

xpath

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