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need to extract for iteration through all values contained in <genre>XXXXX</genre> elements in an XML file.

Posted on 2006-11-28
Medium Priority
Last Modified: 2013-11-23
I need to extract for validation against a controlled list of acceptable values all of the items contained in a <genre>xxxx</genre> xml file.  I could do this by writing my own string parser, but I'm guessing there is a cleaner, "best practice" kind of way to do this using JDOM, SAX or another xml parser.  Help appreciated.
Question by:wizcarl
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LVL 12

Accepted Solution

enachemc earned 1200 total points
ID: 18032290
you could use XPath for this. The string for this would be "//genre".

XPathFactory factory = XPathFactory.newInstance();
XPath xpath = factory.newXPath();
PathExpression expr = xpath.compile("//genre");
Object result = expr.evaluate(doc, XPathConstants.NODESET);

 NodeList nodes = (NodeList) result;
        for (int i = 0; i < nodes.getLength(); i++) {

Author Comment

ID: 18033190
Sorry for the uneducated followup, but I just downloaded the org.apache.xalan jar file and it doesn't contain the XPath nor XPathFactory classess.  Do you know where I can get these jar files?
LVL 12

Expert Comment

ID: 18034931
javax.xml.xpath.XPathExpression (for PathExpression, sorry for the typo)

All of the above are included in the Java 1.5 SDK
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LVL 35

Expert Comment

ID: 18035135

Author Comment

ID: 18036315
Thank you.  I made these changes, and now the code is throuwing an java interal error at the line:

Object result = expr.evaluate(doc, XPathConstants.NODESET)

I think I'm feeding it the wrong kind of input object.  In my code, "doc" is  a string variable that contains all of the xml.  Any ideas of what it needs to be?
LVL 12

Expert Comment

ID: 18036398
for a more simpler and complete example, check out http://www.vipan.com/htdocs/xmlHelp.html
You should supply a parsed document or xml element, not a string.

Author Comment

ID: 18036656
Just as a follow up, I tried changing the "doc" variable from a String to an Object and it thre the same error:

Exception in thread "main" java.lang.ClassCastException: java.lang.String
      at com.sun.org.apache.xpath.internal.jaxp.XPathExpressionImpl.eval(XPathExpressionImpl.java:115)
      at com.sun.org.apache.xpath.internal.jaxp.XPathExpressionImpl.eval(XPathExpressionImpl.java:97)
      at com.sun.org.apache.xpath.internal.jaxp.XPathExpressionImpl.evaluate(XPathExpressionImpl.java:178)
      at org.nines.NinesCollexImporter.validateValues(NinesCollexImporter.java:576)
      at org.nines.NinesCollexImporter.main(NinesCollexImporter.java:116)
LVL 35

Assisted Solution

girionis earned 800 total points
ID: 18036677
The "doc" should be of Document type and not String, otherwise you cannot perform xpath queries on it. YO should turn the string into an XML document first before you proceed.

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