Edwin,
I hope you don't mind my posting this exchange on the mailing lists, as it could be important to a lot of JXPath users.
You are making a very good point!
At this point I cannot change API that has already been released. However the issue is real and needed to be addressed, so what I have done instead is allow for the namespace mappings to be inheritable via child contexts, just like extension functions, locale etc.
So, the way to reuse mappings will be as follows:
1. You create a reusable "parent" context (which BTW does not even have to have a context node).
JXPathContext pmap = JXPathContext.newContext(null);
2. Register namespaces:
pmap.registerNamespace("foo", "http://foomatic.bar/foo";)3. Use this context as a parent every time you create a new JXPathContext:
JXPathContext context = JXPathContext.newContext(pmap, xmlDocument)
4. Use the mapped prefixes in your xpaths:
String baz = (String) context.getValue("foo:bar/foo:baz");In order to take advantage of this new functionality, you will need to use the HEAD branch from CVS (or the nightly build starting tomorrow).
I hope this helps,
Thank you for the insightful suggestion,
Happy New Year,
- Dmitri
----- Original Message ----- From: "Edwin de Jong" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, December 22, 2004 11:20 AM
Subject: JXPath and namespaces
Hi Dmitri,
Recently we have begun to incorporate the new version of JXPath 1.2 into our
current products. One of the (in my eyes bennevicient) changes is related to
the stricter use of namespaces.
Nevertheless, I feel a design flaw has been made in implementing them. Right
now the prime location of changing namespaces is in the instance of the
JXPathContext class. However, these namespace changes are applied to the
supplied JXPaths. So instead of applying a namespace to a context, it should
be applied to the search string (or have additional methods which allow an
instance of a class that maps from prefixes to URI's). This way, binding can
be seperated from context and search criteria.
Example code snippet:
--- cut here ->8---------------------------
JXPrefixMap pmap = JXPrefixMap.getInstance(); pmap.add("foo", "http://foomatic.bar/foo";); // or JXPrefixMap pmap = xmlContainerInstance.getPrefixMap();
JXPathContext context = JXPathContext.newContext(xmlDocument);
// either: String baz = (String) context.getValue("foo:bar/foo:baz", pmap);
// or:
String baz = (String) context.getValue(new JXPathExpression("foo:bar/foo:baz",
pmap));
System.out.println("Hello world: "+baz+"!");
--- cut here ->8---------------------------
Hope this makes some sense. It will make refactoring our code much easier since we don't always use JXPathContext's as our leading datasource (sometimes the context changes, but the query stays the same).
Regards,
Edwin de Jong -- Edwin de Jong
eMAXX B.V. Kopersteden 22-4 P.O. Box 157 7500 AD Enschede The Netherlands tel. +31 53 484 83 21 fax. +31 53 484 83 23
http://www.emaxx.nl
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