for循环中的XPath求值始终从第一次迭代返回节点的值

Question

I am trying to extract values from a node using a method which is invoked within a for loop.

Every time the Method is invoked, the xpath.evaluate only evaluates the original node that was first passed into the method.

-Sample Node

<doc>
  <str name="subcategory">xyzabc</str>
  <str name="type">QAs</str>
  <str name="id">1234</str>
</doc>

-- for loop where invoked

 ArrayList<Node> responseNodeList = parseResponse(*document as string*);   
 for(int k = 0;k<responseNodeList.size();k++){
                Result resultNode = new Result();

                resultNode.setUrl(new URL(getAttributeValue(responseNodeList.get(k),resultUrl)));
                resultNode.setId(new String(getAttributeValue(responseNodeList.get(k),resultId)));
}

-- Method where i extract the value

private String getAttributeValue(final Node responseNodeUrl, String attribute) throws SearchException {
        try {   
        Node evalNode = null;
        evalNode = responseNodeUrl;

        try {
            nodelisttostr(responseNodeUrl); // This is what i am printing out the node.. where we dont have a problem
        } catch (TransformerFactoryConfigurationError e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (TransformerException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }   

        XPath xPath = XPathFactory.newInstance().newXPath();
        XPathExpression expr = null;
         expr = xPath.compile("/doc/str[@name='"+attribute+"']");  
        String result ;
        result=(String) expr.evaluate(evalNode,XPathConstants.STRING);  
        xPath.reset();
        System.out.println("++++++++"+result); //But when i print this out, it always prints the same value

        return result;
    } catch (XPathExpressionException e) {
        log.error("Error in SearchEngine:getAttributeValue:: "+e.getMessage());
        throw new SearchException(e);
    }
}

Answer 1

Solved..

The XpathExpression was always picking up the first node passed to the method and for some reason it seemed like it was cached, I changed my evaluation string to look like expr = xPath.compile(".//str[@name='"+attribute+"']"); and then the evaluate method now pics up the current document.

Thank you All.

Answer 2

If on your XML above, you use:

//doc/str/@name

You will get:

Attribute='name="subcategory"'
Attribute='name="type"'
Attribute='name="id"'

If you use contains in the XPath expression on your XML above ie

//doc/str/@name[contains(.,'e')]

then you will get:

Attribute='name="subcategory"'
Attribute='name="type"'

But I think you want to just want to do the following with your code:

change this:

expr = xPath.compile("/doc/str[@name='"+attribute+"']"); 

to this ie add an extra / :

expr = xPath.compile("//doc/str[@name='"+attribute+"']");

To evaluate all nodes instead of just the first.

I hope this helps!