It appears that one of the most popular themes in Java development in 2008 has been the Java Persistence API (JPA). I base this statement on the recent announcements that JPA-focused articles appeared in the Top Ten lists of articles for both Oracle Technology Network (OTN) and JavaLobby.
UPDATE (1 January 2009): Since the original posting of this article, the popularity of JPA in 2008 has been further proven by two JPA-related articles making JavaWorld's 2008 Top Ten and by a JPA-related article on EclipseLink making the ElipseZone Top Ten of 2008. See updates at end of this blog for additional details on these.
The article Looking Forward to JPA 2.0 (including Part 2) came in at #6 in the JavaLobby Top Ten Articles of 2008. This two-part article looks at what we can expect with JPA 2.0 (JSR 317). As a side note, EclipseLink will be the reference implementation of JPA 2.0.
My article Basic Java Persistence API Best Practices ended up being the fifth most popular article on Oracle Technology Network's Best of 2008: The Most Popular Tech Articles and How-Tos Published by OTN This Year.
It seems to me that it is more than coincidence that would explain two articles so highly focused on the Java Persistence API being listed in the Java-centric JavaLobby's Top Ten as well as the more general OTN Top Ten. The popularity of these articles is a reflection on the popularity and level of interest in the topic itself.
As further evidence of JPA's popularity in 2008, witness the series of articles in JavaWorld on JPA (Understanding the Java Persistence API, Part 1 and Understanding the Java Persistence API, Part 2) that appeared in early 2008. The fact that the editors at Oracle Technology Network, JavaLobby, and JavaWorld all published articles on JPA in 2008 is further evidence of the popularity of the topic. These editors strive to ascertain what is important to readers and prospective readers and it seems clear that JPA was one of those themes that was widely popular.
For very simple applications, I still prefer Spring JDBC. However, for more complicated (and more common) applications, I have found JPA-compliant implementations to be my object-relational mapping (ORM) tools of choice. It seems clear that 2008 has been a great year for interest in the Java Persistence API. This is not all that surprising when one considers the many advantages of JPA: same data access code across Java SE, Java EE web, and Java EE EJB; ability to switch between specification-compliant implementations, and ease-of-use with features such as configuration by exception (convention over configuration) and the ability to override in-code annotations with external XML configuration.
UPDATE (30 December 2008): An article introducing EclipseLink made the top ten list (#2) of the ten best articles in 2008 at EclipseZone.
UPDATE (1 January 2009): JavaWorld has put out its 2008 top ten (based on page views) and JPA is a focus of two of its top ten articles. Specifically, the article iBATIS, Hibernate, and JPA: Which is Right for You? was the fourth most popular article and Understanding JPA was the sixth most popular. A screen snapshot of the JavaWorld Top Ten of 2008 is shown next: