Want to try JPA or Spring? But you have an old software system, and don't have the luxury of a clean new software project?
Add Spring and/or Hibernate to your old Java software system. Instead of waiting, put in a STEALTH upgrade that is low-friction, low cost, and low visibility to the customers and others around the project. You can boast later when the system succeeds because of the new technologies.
We've all made some excuses for NOT upgrading the technology of a system. (But we can address each of these):
* I can't afford to overhaul the whole system
* Our Java servers don't support it, we cannot upgrade the Java server
* What will my manager or customer think?
Upgrade the whole system?
No software engineer has time & money to do that. So I suggest looking for a new feature and only upgrading that part of the system: this is the low-friction part. There's no need to overhaul every working DAO, leave them for later until you need to change them to keep costs down. Maybe you've got a new model object you are adding, why not use Spring and Hibernate to manage that object? Who needs to drag around the old EJB2 patterns, or your own home-grown JDBC DAO's just to keep the system consistent? In the end, you may finish the feature upgrade faster because you used Hibernate and Spring Transactions. After you try it, you may decide to convert other DAO's as changes happen to those parts of the system. This can all be done under the radar - Stealth mode - without kicking off a major overhaul of every DAO in the system.
Upgrade my app server?
You may think that your Java App server doesn't support Hibernate or Spring, but Hibernate and Spring are simply jar libraries that can be deployed inside your web app, and do not require an upgrade to your server. So go ahead and add the jar files inside your web app (or WAR or EAR file), and use them freely. If you'd like to use EJB3, and you have an app server that does not support it like Tomcat or IBM, you could use JBoss Embeddable EJB3 container- yet another free, OSS jar library that can be put inside your web app. Hibernate and Spring can even work in Java 1.4, (EJB3 and JPA need Java5).
What will people think?
Your customers and users of the system may not be able to spell JDBC, but that's OK, besides that is why they pay YOU, the software engineer. So they will not care whether you use Hibernate, OpenJPA, iBATIS, or raw JDBC. Many of your managers will not care either, as long as it doesn't cause the boat to rock in server operations (and it won't as described above in upgrading your app server). If your customer/manager is curious, you can tell him that many good things will be coming: like short development times, developers will be excited about the new technology. If you need to convince other developers, remind them that these technologies are popular for a reason, and its a good skill for a software developer to have for the future.
Marketing this kind of strategy is a challenge. Selling this idea to your customers, colleagues, and managers is probably a bigger challenge than actually making the software changes. Just keep in mind that some people will not care, and don't need to be scared by change, so leave them out of the conversation except to say that their new features will be coming soon. NOT telling them is not deception or evil, its just too much information (TMI), and it can sometimes be scary. So if they keep asking questions, tell them everything, but remember to tell them that confidence is high, risk is low, and everyone is doing it. The software people who know the system should get excited, not scared, by the new technologies adding power and speed to the system. Consider the alternative - try to hire a Java developer by telling him he gets to maintain old EJB2 CMP. Software engineers run away from those technologies, you won't get anyone to hire on without lying, and your current developers will leave in short order too.
The Stealth approach can avoid the hoopla and resistance that happens when any kind of change is suggested. So take advantage of the trust they place in you to make the right technology choice. You will get to use new technologies, your system will be better, and nobody needs to be the wiser. In the end you may get it all done faster and easier too.