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?

Solution 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]

Solution 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']