Jodd provides great, little, stand-alone transaction manager, JTX. It is a significant change in traditional thinking, since no (j2ee) application server is required; JTX may be used in any Java code.
JTX is built to be roughly similar to JTA up to certain point; but without complexity. It's goal is to works well with every-day web/desktop applications; not to manage heavy-weight requirements such as transactions across multiple domains, etc.
In a nutshell JTX provides a transaction model that supports transaction demarcation over any number of resources - of any kind. Of course, the emphasis is put on database transactions; there is a layer built on top of JTX to integrate it well with Db and Proxetta frameworks. JTX may be used programmatically through simple API or declaratively using annotations.
JTX in action
A picture is worth a thousand words, a good code example even more;) Here is one real-life example how JTX is used declaratively.