XPath search by "id" attribute , giving NPE - Java

Question

All,

I have multiple XML templates that I need to fill with data, to allow my document builder class to use multiple templates and insert data correctly

I designate the node that I want my class to insert data to by adding an attribute of:

id="root"

One example of an XML

<?xml version="1.0" encoding="UTF-8" standalone="yes" ?> <SiebelMessage MessageId="07f33fa0-2045-46fd-b88b-5634a3de9a0b" MessageType="Integration Object" IntObjectName="" IntObjectFormat="Siebel Hierarchical" ReturnCode="0" ErrorMessage="">     <listOfReadAudit >         <readAudit id="root">             <recordId mapping="Record ID"></recordId>             <userId mapping="User ID"></userId>             <customerId mapping="Customer ID"></customerId>             <lastUpd mapping="Last Updated"></lastUpd>             <lastUpdBy mapping="Last Updated By"></lastUpdBy>             <busComp mapping="Entity Name"></busComp>         </readAudit>     </listOfReadAudit> </SiebelMessage> 

Code

expr = xpath.compile("//SiebelMessage[@id='root']"); root = (Element) expr.evaluate(xmlDoc, XPathConstants.NODE); Element temp = (Element) root.cloneNode(true); 

Using this example: XPath to select Element by attribute value

The expression is not working:

//SiebelMessage[@id='root']

Any ideas what I am doing wrong?

Answer 1

Try this:

//readAudit[@id='root'] 

This selects all readAudit elements with the id attribute set to root (it should be just 1 element in your case).

You could make sure it returns maximum 1 element with this:

//readAudit[@id='root'][1] 

Answer 2

What you are doing is selecting SiebelMessage nodes with the attribute id='root'.

But the SiebelMessage doesn't have an id, it's the readAudit you are after. So either do

//readAudit[id='root'] 

or

//SiebelMessage//readAudit[id='root']