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Why would I use Scala/Lift over Java/Spring?

I know this question is a bit open but I have been looking at Scala/Lift as an alternative to Java/Spring and I wonder what are the real advantages that Scala/Lift has over it. From my perspective and experience, Java Annotations and Spring really minimizes the amount of coding that you have to do for an application. Does Scala/Lift improve upon that?

Solution

  • Let's assume we're equally comfortable in Scala and Java, and ignore the (huge) language differences except as they pertain to Spring or Lift.

    Spring and Lift are almost diametrically opposed in terms of maturity and goals.

    • Spring is about five years older than Lift
    • Lift is monolithic and targets only the web; Spring is modular and targets both web and "regular" apps
    • Spring supports a plethora of Java EE features; Lift ignores that stuff

    In a sentence, Spring is heavyweight and Lift is lightweight. With sufficient determination and resources you can turn that on its head, but you would need a lot of both.

    Here are concrete differences that stuck in my mind after working with both frameworks. This isn't an exhaustive list, which I can't compile anyhow. Just what seemed most interesting to me...

    1. View philosophy

      Lift encourages placing some view material in snippet/action methods. Snippet code especially will be sprinkled with programmatically generated form elements, <div>s, <p>s, etc.

      This is powerful and useful, especially since Scala has a builtin language-level XML mode. One can write XML inline within Scala methods, including variable bindings in braces. This can be delightful for very simple XML services or mockups of services -- you can bang out a suite of HTTP response actions all in one splendidly terse file, without templates or much attendant configuration. The downside is complexity. Depending on how far you go, there's either a fuzzy separation of concerns between view and logic, or no separation.

      In contrast, regular use of Spring for webapps enforces a strong separation between the view and everything else. I think Spring supports several templating engines, but I've only used JSP in anything serious. Doing a Lift-inspired "fuzzy MVC" design with JSP would be madness. This is a good thing on larger projects, where the time to just read and understand can be overwhelming.

    2. Object-Relational Mapper Choices

      Lift's builtin ORM is "Mapper". There's an upcoming alternative called "Record", but I think it's still considered pre-alpha. The LiftWeb Book has sections on using both Mapper and JPA.

      Lift's CRUDify feature, cool as it is, only works with Mapper (and not JPA).

      Of course, Spring supports a panoply of standard and/or mature database technologies. The operative word there is "supports". Theoretically, you can use any Java ORM with Lift, since you can call arbitrary Java code from Scala. But Lift only really supports Mapper and (to a much lesser extent) JPA. Also, working with nontrivial Java code in Scala is currently not as seamless as one might like; using a Java ORM, you will probably find yourself either using both Java and Scala collections everywhere or converting all collections in and out of the Java components.

    3. Configuration

      Lift apps are configured pretty much entirely through a method an application-wide "Boot" class. In other words, the config is done through Scala code. This is perfect for projects with brief configurations, and when the person doing the configuring is comfortable editing Scala.

      Spring is pretty flexible in terms of configuration. Lots of conf options can be driven either through XML configuration or annotations.

    4. Documentation

      Lift's documentation is young. Spring's docs are pretty mature. There's no contest.

      Since Spring's docs are already nicely organized and easy to find, I'll review the docs I found for Lift. There are basically 4 sources of Lift documentation: the LiftWeb Book, the API Docs, LiftWeb's Google group, and "Getting Started". There's also a nice suite of code examples, but I wouldn't call them "documentation" per se.

      The API docs are incomplete. The LiftWeb Book has been published on trees, but it's also freely available online. It is really useful, although its decidedly didactic style irritated me at times. It's a little long on tutorial and short on contract. Spring has a proper manual, which Lift lacks.

      But Lift does have a nice set of examples. If you're comfortable reading the Lift code and example code (and you know Scala well already), you can work things out in fairly short order.

    Both frameworks are compelling. There's a broad range of apps where you can choose either and do well.