Stephan Schmidt has blogged on the ORMs being a thing of the past. While he emphasizes on ORMs' performance concerns and dismisses them as leaky abstractions that throw LazyInitializationException, he does not present any concrete alternative. In his concluding section on alternatives he mentions ..
"What about less boiler plate code due to ORMs? Good DAOs with standard CRUD implementations help there. Just use Spring JDBC for databases. Or use Scala with closures instead of templates. A generic base dao will provide create, read, update and delete operations. With much less magic than the ORM does."
Unfortunately, all these things work on small projects with a few number of tables. Throw in a large project with a complex domain model, requirements for relational persistence and the usual stacks of requirements that today's enterprise applications offer, you will soon discover that your home made less boilerplated stuff goes for a toss. In most cases you will end up either rolling out your own ORM or start building a concoction of domain models invaded with indelible concerns of persistence. In the former case, obviously your ORM will not be as performant or efficient as the likes of Hibernate. And in the latter case, either you will end up building an ActiveRecord model with the domain object mirroring your relational table or you may be more unfortunate with a bigger unmanageable bloat.
It's very true that none of the ORMs in the market today are without their pains. You need to know their internals in order to make them generate efficient queries, you need to understand all the nuances to make use of their caching behaviors and above all you need to manage all the reams of jars that they come with.
Yet, in the Java stack, Hibernate and JPA are still the best of options when we talk about big persistent domain models. Here are my points in support of this claim ..
- If you are not designing an ActiveRecord based model, it's of paramount importance that you keep your domain model decoupled from the persistent model. And ORMs offer the most pragmatic way towards this approach. I know people will say that it's indeed difficult to achieve this in a real life world and in typical situations compromises need to be made. Yet, I think if you need to make compromise for performance or whatever reasons, it's only an exception. Ultimately you will find that the mjority of your domain model is decoupled enough for a clean evolution.
- ORMs save you from writing tons of SQL code. This is one of the compelling advantages that I have found with an ORM that my Java code is not littered with SQL that's impossible to refactor when my schema changes. Again, there will be situations when your ORM may not churn out the best of optimized SQLs and you will have to do that manually. But, as I said before, it's an exception and decisions cannot be made based on exceptions only.
- ORMs help you virtualize your data layer. And this can have huge gains in your scalability aspect. Have a look at how grids like Terracotta can use distributed caches like EhCache to scale out your data layer seamlessly. Without the virtualization of the ORM, you may still achieve scalability using vendor specific data grids. But this comes at the price of lots of $$ and the vendor lock-ins.
Stephan also feels that the future of ORMs will be jeopardized because of the advent of polyglot persistence and nosql data stores. The fact is that the use cases that nosql datastores address are very much orthogonal to those served by the relational databases. Key/value lookups with semi-structured data, eventual consistency, efficient processing of web scale networked data backed with the power of map/reduce paradigms are not something that your online transactional enterprise application with strict requirements of ACID will comply with. So long we have been trying to shoehorn every form of data processing with a single hammer of relational databases. It's indeed very refreshing to see the onset of nosql paradigm and it being already in use in production systems. But ORMs will still have their roles to play in the complementary set of use cases.