The XQJ API (JSR-225) is currently in early draft at the JCP. Currently I use the Saxon API in the work I do with XQuery. Here is an example from mjg.md:

    Configuration c = new Configuration();
    StaticQueryContext qp = new StaticQueryContext(c);
    XQueryExpression xe = qp.compileQuery(query);
    DynamicQueryContext dqc = new DynamicQueryContext(c);
    Source source = new StreamSource(new URL(url).openStream());
    DocumentInfo di = qp.buildDocument(source);
    dqc.setContextNode(di);
    List result = xe.evaluate(dqc);

The result is a List of DOM elements that are the result of the query. I was hoping he would talk more about using XQuery against relational databases which I think is a powerful way to display relational data in markup. You ought to be able to directly transform most XQueries directly into their SQL equivalents. The speakers product has this sort of thing but I imagine a standard transform would be generally useful through a new XQuery function that allows relational source documents. Here is what the standard API will look like:

XQConnection conn = xqds.getConnection();    
XQExpression expr = conn.createExpression();    
XQResultSequence result = expr.executeQuery(query); 

A little less verbose with a more J2EE feel to it. I'd really need to try it out to see what I think.

The next talk I went to is the XQuery talk by Jason Hunter. His company has a large XML repository that is accessed through XQuery. The talk is similar to the talk last year with a new demo and some information about XQJ. Unfortunately, his talk focuses on using XQuery against an XML database instead of at runtime. Most of the use cases for me involve processing transient XML messages.