[Haskell-cafe] Integrating Haskell into a J2EE environment

Paul Hudak paul.hudak at yale.edu
Wed Oct 6 15:59:15 EDT 2004

I wouldn't write off Haskell so quickly.  All of what Shoeb describes 
concerning DSL issues might be much more easily solved in Haskell, and 
will certainly be more flexible than a hard-wired approach.  The J2EE 
interface might be ugly, but if the functionality needed is not too 
great it might not be too bad.  Generally speaking, these kinds of apps 
-- in this case "a DSL for high-level business rules" -- sounds like 
just the sort of thing that Haskell is good for.


Doug Kirk wrote:
> You're going to spend alot of time marshalling between Java and Haskell 
> values, and you'll either have to do it via JNI or by using pipes [as in 
> System.exec("haskellprogram param param param")], both of which are ugly 
> for a Java app.
> Have you looked at Jython and JRuby? Jython is an implementation of a 
> Python interpreter in 100% Java, and JRuby implements a Ruby interpreter 
> in 100% Java.
> Those might get the job done faster than having to delve into the native 
> layer. (Not to mention learning how to use Haskell in order to implement 
> what you want--not a trivial task in itself!)
> Take care,
> --doug
> On Oct 5, 2004, at 4:33 PM, Bhinderwala, Shoeb wrote:
> Hi All,
> I am new to Haskell and this mailing list.
> We have a system that uses a custom high-level language to express
> high-level business rules. Expressions in the high-level language get
> compiled to Java bytecode. We express the grammar using BNF notation as
> required by the javacc parser tool. This is then converted to an AST
> using jjtree and from there we build the final Java code. Our language
> could be considered a domain-specific language (DSL) and is used by our
> business users to express very high-level business logic. The language
> currently is very limited - we support boolean logic, function
> invocations and if-then statements. We want to convert it into a more
> powerful scripting language so that even lower level business logic can
> be expressed in it.
> I came across a few papers that talk about writing a DSL with Haskell as
> the underlying support language. How is this done. Is it possible to
> create a sort of domain specific business scripting language easily. How
> does that then compile to Haskell code. And how can the Haskell code be
> invoked from Java.
> Essentially, I am thinking if I could use a Haskell like DSL language to
> express our business rule logic and then be able to integrate into and
> invoke the logic from a J2EE app server environment. Has anybody done
> anything like this with Haskell.
> -- Shoeb
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Professor Paul Hudak
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Yale University                   FAX:    (203) 432-0593
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