Blogs, by their nature, have certain advantages over other forms of communicating details on a specific technology. First, it is difficult to think of a faster way to communicate new information than a blog. Blog entries typically don't have the review process of a formal article and, in fact, are often even written more quickly by an author than an article would be. That, of course, is also the primary disadvantage of blogs -- they are not reviewed and their quality varies greatly from downright incorrect to highly valuable, informative, and leading edge.
Another advantage of the blog medium of communication is that it allows for highly focused coverage that appeals to a narrow audience that might not justify publication of a book or article. While books can be more detailed than articles, there is typically a significant period of time between a book's initial concept and its publication. In fact, it is this advantage of blogs (the ability to focus on narrow topics) that I am taking advantage of with this particular blog entry. I am focusing on some of the most useful JPA-related blogs I have encountered because I could not spend that much time on them in the article.
A final advantage of blogs over more traditional software development literature mediums is that many highly skilled, highly experienced, and knowledgeable developers may be more willing to write a blog entry or respond to a blog entry than they would be to take the time to write and publish an article or book.
Because of these advantages of the blog as a form of communication, it is useful for a JPA developer to read from and learn from the work of others as covered in JPA-related blogs. With these advantages established, it is time to look at some of the JPA-related blogs that I have found most useful in my own JPA work.
What Michael Bouschen's Blog lacks in terms of number of entries, it makes up for in terms of the unusually high quality of the entries. As of this writing, there are the only two entries as far as I can tell. Still, the two entries are useful enough to JPA developers to warrant this blog getting referenced in the article. The first entry, Using Relationships in the Java Persistence Query Language (July 2006), provides thorough but concise coverage of different types of joins that can be performed in JPA Query Language along with some other useful details about JPA Query Language relationships. I found the next blog entry, Java Persistence Query Return Types (April 2007), to be even more interesting and useful. This entry is also thorough but concise in its coverage of various methods of querying in JPA.
Wonseok Kim's Blog has many blog entries, including a large number on JPA, TopLink Essentials, and other JPA-related themes. There are too many entries to cover them individually here, but a good sample of the value provided in this blog can be found in the blog entry Understanding the Cache of of TopLink Essentials (GlassFish JPA). Of course, this will most interest users of TopLink Essentials as their JPA provider, but I imagine that is a fairly large group considering that it is the JPA 1.0 reference implementation and is bundled with GlassFish.
Sahoo's Blog is another valuable source of detailed JPA information. Sahoo has also posted several JPA-related entities, so I narrow my focus to two closely related examples. In the blog entries A javac Plugin to Manage Your persistence.xml and An annotation processor to update your persistence.xml during javac, Sahoo demonstrates how to use custom annotation processing to generate the
persistence.xmlfile from in-source annotations in the Java code. This is similar to what I demonstrated for generating the
orm.xmlfile (or equivalent multiple files) from in-source annotations in the OTN article Better JPA, Better JAXB, and Better Annotations Processing with Java SE 6.
There are, of course, many other blogs covering the Java Persistence API. Some (such as On Persistence [Shaun Smith], Java Persistence [Doug Clarke], and the EclipseLink Team Blog) are pretty much focused on JPA. Others (such as my blog, Chris Maki's blog, and the AMIS Technology Blog) have a more general software development focus, but occasionally feature JPA-specific blog entries.
JPA-related blog entries can provide many advantages such as timeliness, access to authoritative experts that might not wish to write a book or article, greater focus on details that don't warrant a full book or article, and other advantages associated with the so-called Web 2.0 social network. The one caveat is that not all blogs are created equal. The ones I have highlighted here are, in my opinion, of very high value and quality. However, especially with blogs you are not familiar with, it always makes sense to balance what you read in a blog entry with your own experience and with the experience of others as reflected in their blogs, articles, and books.