Groovy & BeanShell: Dynamic vs Scripting Languages

In my previous post I talked about the fundamental difference between Groovy and BeanShell and in one of the comments I was asked to elaborate on why exactly Groovy is dynamic and BeanShell is not. So here it, BeanShell is a scripting language, it is to Java what VBScript is to VB, the syntax is near identical, you can copy and paste Java code into BeanShell and vica versa. This makes it highly useful for doing things like testing Java code in isolation, or trying out a Java API through an interactive BeanShell console.

It is 'dynamic' in the sense that it uses reflection to achieve a lot of these goals, but beyond the aformentioned use cases I would not choose BeanShell over Java to implement say a build system, or a my web actions, or do text processing, advanced regex, output templates, as a view technology, this list can go on...

The reality is that BeanShell does not provide any productivity gain so to choose to use it for a task over Java (rather than use it to script Java) has no real benefit and this is because it does not have any of the true features of a dynamic language like Ruby or Groovy. I'm a big fan of WebWork and I've been using Groovy to write XWork actions because the advantages are clear, I can save/reload changes, I can use closures to manipulate and sort my data model:

projects.findAll { it.status == 'open' }.sort { it.name }

I can use GStrings, a concept known as string interpolation in languages like Perl and Ruby, and multi-line string support to easily manipulate strings:

def user = User.get(1)

def message = '''
Dear ${user.name},

Thank you for registering with xxx site,

Your password is: ${user.password}.

See you soon!
The Site
'''


There are many more examples of the kind of expressiveness mentioned above that Groovy allows in its syntax, but more importantly than all these syntatic niceties and what makes Groovy truely 'dynamic' is how methods (as well as constructors, properties etc.) are dispatched. Groovy has the concept of a MetaClass and it contains the methods that a class 'really' has as well those added dynamically at runtime, allowing new behaviours to be attached to new and existing classes. This is a feature Grails uses extensively to add behaviours to controllers, domain classes, tag libraries etc. all while still retaining the ability to use inheritence.

The reality is that Groovy and BeanShell are not really competing with each other at all, and address different problems entirely: BeanShell the scripting language for Java and Groovy the dynamic, agile language for the JVM. That is why I hope that instead of seeing articles like those written recently, we'll see some from the same people entitled "Using BeanShell to Prototype Java Code" or "Using Groovy to Power your Build System" as writing "Groovy is rubbish, and BeanShell is great" or vica versa is really not helping any newcomer who is interested in this space make an informed decision on which is the appropriate language for their use case.