InfoQ

News

XQuery Java API JSR 225 Available for Public Review

Posted by Abhay Bakshi on Jul 03, 2007 11:28 AM

Community
Java
Topics
Data Access
Tags
XQuery
The first public review draft of JSR 225: XQuery API for Java has been posted for review.  The spec (being led by Oracle) aims to provide standard programmatic access for XQuery implementations in Java.  XQJ is a generic XQuery data access framework, which provides a uniform interface on top of a variety of different XQuery implementations.

The W3C XQuery is a query language for XML. Wikipedia defines it's function as providing the means to extract and manipulate data from XML documents or any data source that can be viewed as XML, such as relational databases or office documents.XQuery uses XPath expression syntax to address specific parts of an XML document. One of the language syntax requirements for XQuery is that the Query language MUST be convenient for humans to read and write. The XQuery language now has both a human-readable syntax and an XML-based syntax. The XML-based syntax for XQuery is available at XQueryX 1.0.

A basic XQJ expression in Java looks like (from the spec):
...
// establish a connection to the XQuery engine
XQConnection conn = xqds.getConnection();

// create an expression object that is later used
// to execute an XQuery expression
XQExpression expr = conn.createExpression();

// the XQuery expression to be executed
String es = "for $n in fn:doc('catalog.xml')//item " +
"return fn:data($n/name)";

// execute the XQuery expression
XQResultSequence result = expr.executeQuery(es);

// process the result (sequence) iteratively
while (result.next()) {
// retrieve the current item of the sequence as a String
String str = result.getAtomicValue();
System.out.println("Product name: " + str);
}

// free all resources allocated for the result
result.close();

// free all resources allocated for the expression
expr.close();

// free all resources allocated for the connection
conn.close();
...
While the XQJ spec has been led by Jim Melton (Oracle), its JCP expert group involves members including Jason Hunter, DataDirect , BEA Systems et al. Industry leaders outside of JCP have also been following the XQJ specification, contributing ideas, and improving their own products for conformity. Michael Kay - creator of Saxon and author of XPath 2.0 Programmer's Reference - writes:
It's the first new version for about a year, and the spec is developed under conditions of absolute secrecy, so I was interested to see what was going to be in it. I wasn't expecting too much, because most of my comments on the previous draft had been politely rejected (about 8 months after I submitted them, with no open discussion). Sure enough, they've tidied up quite a lot of little things, but the overall design hasn't changed much. (It's sufficiently incompatible, however, that most applications will have to be tweaked: not rewritten, but amended here and there.)
It's still uncompromisingly based on a client-server, connection-oriented model where the application lives on a different machine from the database (so 1980s!). ... prepared expressions are not thread-safe - you can't compile an expression and then run it in multiple threads simultaneously, because the XQPreparedExpression holds its own dynamic execution context.
Are there any good points? Yes, quite a few. The mapping of XPath values (the 19 primitive data types) to equivalent objects in Java is done reasonably well - much better than JAXP ... This version also has a full representation in Java terms of all XPath types ...
Still, I think one can do better. ...
The W3C XQuery specification and 8 related specifications (including XSLT 2.0 and XPath 2.0) were submitted to the W3C on June 8 2006. Many of them were updated on 23 January 2007. The industry has already begun embracing XQuery in their products, even JSR 170/Java Content Repositories use it as their standard query mechanism. InfoQ has been tracking development of XQuery specification, XQJ specification, and the implementations.
article by Tomek Górski Posted Oct 13, 2007 5:48 AM
Article by Andrew News Posted Feb 3, 2008 10:39 AM
  1. Back to top

    article

    Oct 13, 2007 5:48 AM by Tomek Górski

    Thanks for another very interesting article. Keep up the good work. Regards Pozycjonowanie Tom

  2. Back to top

    Article

    Feb 3, 2008 10:39 AM by Andrew News

    Interesting Article, thank you for sharing your thoughts.

Educational Content

Bindings, Platforms, and Innovation

This presentation focuses on the Internet and separating myth from fact, history from the future, and the mundane from the imaginative. Bob Frankston presents a vision of what could and should be.

Orchestrating Long Running Activities with JBoss / JBPM

This article explores the use of JBoss and jBPM to implement design solutions that effectively address the issue of orchestrating long running activities.

Neo4j - The Benefits of Graph Databases

This presentation covers the use of graph databases as an optimal solution for data that is difficult to fit in static tables, rapidly evolving data or data that has a lot of optional attributes.

Realistic about Risk: Software development with Real Options

This session introduces Real Options and shows how it can help in running your project. Real Options is a decision-making process that can be used to manage risk.

Communication Flexibility Using Bindings

This article discusses the use of bindings on services and references (including the instance of non-configured bindings) as the means to implement SCA communications in a Web and SOA environment.

Writing DSLs in Groovy

After a short introduction to DSLs, Scott Davis plays with the keyboard showing how to approach the creation of a DSL by typing working snippets of Groovy code that get executed.

Scaling Agile with C/ALM (Collaborative Application Lifecycle Management)

IBM Rational and InfoQ present, Scaling Agile with C/ALM, an eBook showing organizations how to become “finely tuned software delivery machines” by enabling team integration and scaling.

Concurrent Programming with Microsoft F#

Amanda Laucher presents a real life enterprise application written in F#. She shows actual code snippets, explaining design decisions and suggesting how to use some of the F# constructs.