Stephen Colebourne who is frequently commenting on the lambda-dev and other Java 8 mailing lists, has recently published an idea he has been having for a while: ElSql, a new external SQL DSL for Java.

An example SQL statement is given on the blog posts or on GitHub:

@NAME(SelectBlogs)
  @PAGING(:paging_offset,:paging_fetch)
    SELECT @INCLUDE(CommonFields)
    FROM blogs
    WHERE id = :id
      @AND(:date)
        date > :date
      @AND(:active)
        active = :active
    ORDER BY title, author
@NAME(CommonFields)
  title, author, content

As can be seen, this is almost mere string-based SQL, enhanced with some “hooks” for later use in Java. While Stephen’s idea here is to keep it simple (much simpler than jOOQ for instance) it shows some useful applications of allowing to write external DSLs which resemble SQL even more than jOOQ.

DSL authoring support is becoming a more and more interesting topic in various platforms. Eclipse is developing Xtext, Scala is experimenting with even more powerful Macros. While Xtext doesn’t allow to mix the DSL grammar with Java, Scala’s Macros do precisely that. They allow for simple compile-time checked Scala syntax extension, if you have a powerful enough CPU to compile such source code. Where this could go for jOOQ was discussed on this blog before

For more details, read about ElSql on Stephen’s or the OpenGamma blog:

• http://blog.joda.org/2012/10/elsql-librarydsl-to-manage-sql.html
• http://www.opengamma.com/blog/2012/10/15/elsql-java-library-for-managing-sql