[Haskell-cafe] Integrating Haskell into a J2EE environment

[Doug Kirk]

Yes, I agree, and didn't mean to write off Haskell (at which, I'm 
completely a newbie, trying to learn, and thankful for your book!).

However, I'm a Java pro, and there are many technical issues on the 
Java side that scream at me to keep out of the native arena, especially 
in a J2EE container environment, where funny things can happen with hot 
reloads (dumping old ClassLoaders for new ones), clustering, and the 
like.

So it wasn't out of denigration of Haskell that I made my 
recommendation; far from it...from what I've seen Haskell is perfect 
for implementing DSL's. Rather, from the Java side is where it becomes 
problematic. There have been many problems integrating with native 
libraries from within a J2EE container, and I try to seek the most 
cost-effective way (I'm an independent consultant) to get the problem 
solved for my customers.

--doug

On Oct 6, 2004, at 2:59 PM, Paul Hudak wrote:

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.

   -Paul


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
Chair, Dept of Computer Science   Office: (203) 432-1235
Yale University                   FAX:    (203) 432-0593
P.O. Box 208285                   email:  paul.hudak at yale.edu
New Haven, CT 06520-8285          WWW:    www.cs.yale.edu/~hudak




This communication is confidential and may be legally privileged.  If you are not the intended recipient, (i) please do not read or disclose to others, (ii) please notify the sender by reply mail, and (iii) please delete this communication from your system.  Failure to follow this process may be unlawful.  Thank you for your cooperation.