[armedbear-devel] Question about calling Java

Alessio Stalla alessiostalla at gmail.com
Wed Feb 3 19:00:40 UTC 2010

On Wed, Feb 3, 2010 at 6:46 PM, nitralime <nitralime at googlemail.com> wrote:
> IMHO, the ablity of using Java libraries easily should be an integral
> part of
> every language targeting JVM! I find it very unfortunate that the Java
> integration
> of ABCL is practically (i.e. out of the box) absent.

Why do you say that? ABCL's Java FFI is somewhat verbose, but apart
from this limitation that Mark found, and maybe some things that could
be polished and made more uniform, you can do anything you want.

> On 02/02/2010 05:50 PM, Mark Evenson wrote:
>> Usually, I can find a way to translate given Java code into the ABCL
>> equivalent.  Sometimes it takes quite a while to figure the correct
>> syntax  which I attribute to the organically evolved nature of our Java
>> integration, but I have never found something ultimately unexpressable.
>>    Until now, although I think this has to do with me trying to debug
>> ABCL internals with the ABCL REPL, but I want to document it.  Have I
>> missed some way of making this call?
>> The code:
>>       SimpleString h = new SimpleString("FOO");
>>       Pathname.LOGICAL_PATHNAME_TRANSLATIONS.get(h));
>> LOGICAL_PATHNAME_TRANSLATIONS is a EqualHashTable object whose signature
>> of get() is
>>       LispObject get(LispObject key)
>> This fails
>>       (jcall "get"
>>         (jfield "org.armedbear.lisp.Pathname"
>>         (jnew "org.armedbear.lisp.SimpleString" "FOO"))
>> with the error
>>     The value "org.armedbear.lisp.SimpleString" is not of type JAVA-OBJECT
>> Diving into the code shows that the Java.translateMethodArguments() call
>> is always going to translate the SimpleString argument into a instance
>> of  java.lang.String as this is what SimpleString.javaInstance()
>> returns.  Is there any way to tell JCALL not to perform such translation
>> on its arguments?  JCALL-RAW doesn't convert its return value, but maybe
>> we need a JCALL-NAKED that doesn't translate its arguments?  I suspect
>> that we don't need JCALL-NAKED for anyone not using Java objects that
>> are descendents of org.armedbear.lisp.LispObject but I'm not exactly
>> sure how to prove this claim.
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