[jdom-interest] SAXBuilder: Build document from url fails

[Matthias Klein]

I try to use the REST inteface of Amazon.com to perform ItemSearchRequests.
That interface returns a standard XML file containing the results of the
query.

But when I try to build a Document from the result by

                Document doc = builder.build(url);
                Element root = doc.getRootElement();
                Element items = root.getChild("Items");

I keep getting a NullPointerException. (The url represents the target
endpoint of the Amazon Interface and contains the query parameters)

When I save the XML into a file first and do

                Document doc = builder.build(file);
                Element root = doc.getRootElement();
                Element items = root.getChild("Items");

it works fine.

Why can I not build a Document from a url using the SAXBuilder? (Why do I
have to use the detour via a file?)

The only parameter of the SAXBuilder build() method that works here is the
file. When I try any of the other parameters (such as a Reader or
InputStream) I keep getting the NullPointerException below.
The Exception occurs in the last line: Element items =
root.getChild("Items"); Which looks to me as if the data returned by Amazon
did not make it into the Document.
Why is that?

Thanks

Matt


P.S. Here is the exception: (line 107 is the one mentioned above: Element
items = ...)

java.lang.NullPointerException
        at AmazonConnector.doItemSearch(AmazonConnector.java:107)
        at MidTermProjectMain.main(ProjectMain.java:41)
java.lang.NullPointerException
        at AmazonConnector.doItemSearch(AmazonConnector.java:107)
        at MidTermProjectMain.main(ProjectMain.java:41)