need little help for class loading & invokeDynamics

[Marvin Hansen]

Thank you Rémi, you've saved my day,

and sorry for the typo...

yes it was the signature mis-match and finally,

Object alg = loadedClaZZ.newInstance();
Object o = methodHandle.invokeWithArguments(alg, 21, "+", 21);


is doing the job for me, so it's working now:-)

again, thanks for all your help.
marvin


http://www.marvin-hansen.tel




On 14 January 2011 22:37, Rémi Forax <forax at univ-mlv.fr> wrote:
> On 01/14/2011 09:59 AM, Marvin Hansen wrote:
>> Thansk you Rene,
>
> I think i prefer Rémi or Rémy.
>
> run is declared (int,int,String) and you lookup (int,String,int).
>
> Also the line:
>   methodHandle.invokeWithArguments(21, "+", 21);
> will raise a runtime exception because you forget to pass an instance of
> SimpleMath
> as first argument (run is not static).
>
> Rémi
>
>> visibility is not an issue, since both class&  method are declared
>> public and a normal static call works just fine. I'm sorry
>> I've forgotten to add the simpleMath source but for the sake of
>> completeness I've copied the class
>> at the bottom of the mail.
>>
>> However, it looks much more that I've run into the problem that java
>> cannot directly emit invokedynamic.
>> I understant that the main purpose for invokedynamic was and still is
>> the support of dynamic languages but
>> this limitation seams arbitrary for me. Is there any intention to
>> change it or is that the way invokedynamic should
>> be released?
>>
>> Anyway, thanks for the link I will read it carefully and hopefully I
>> will find a work-around to do an
>> invokedynamic call from my loaded class.
>>
>> Thanks for your helpful advice;
>>
>>
>>
>>
>>
>> public class SimpleMath {
>>
>>      public SimpleMath() {
>>      }
>>
>>      /**
>>       * @param a
>>       * @param b
>>       * @param op
>>       * @return int
>>       */
>>      public int run(int a, int b, String op) {
>>
>>          int returnvalue = calculate(a, b, op);
>>
>>          return returnvalue;
>>      }
>>
>>
>>      private int calculate(int a, int b, String op) {
>>
>>          int ret = null;
>>
>>              switch (op) {
>>                  case "+":
>>                      ret = a + b;
>>                      break;
>>                  case "-":
>>                      ret = a - b;
>>                      break;
>>                  case "/":
>>                      ret = a / b;
>>                      break;
>>                  case "*":
>>                      ret = a * b;
>>                      break;
>>                  default:
>>                      System.err.println("No valid paramter given. Use
>> only :  '+' ; '-' ; '/' ; '*' (String)
>>                                                    as operator and
>> interger as numbers");
>>                      break;
>>              }
>> }
>>
>>
>>
>> http://www.marvin-hansen.tel
>>
>>
>>
>>
>> On 14 January 2011 21:04, Rémi Forax<forax at univ-mlv.fr>  wrote:
>>> On 01/14/2011 06:15 AM, Marvin Hansen wrote:
>>>> Hi Folks,
>>>>
>>>> I've started to work on invokeDynamics but I need a little help to
>>>> understand how to use it right. For learning purpose, I've written a
>>>> little class, that loads another class, does the method look-up and
>>>> (should) execute the located method. The example in the methodHandle
>>>> JavaDoc was my starting point but as usual it's not that easy since it
>>>> works well for JDK classes but not with loading my own class which
>>>> causes a “NoAccessException”.
>>>>
>>>> I suppose that I need to deal with CallSite&    Bootstraping but I've
>>>> not yet figured out how to patch class-loading, methodHandle,
>>>> Bootstraping&    invocation together in order to make it work. The
>>>> JavaDoc says, that before an invokedynamic instruction can be executed
>>>> a CallSite must be linked  via boostrap method that produces a
>>>> methodHandle. That makes sense for me.
>>>>
>>>> However, the CallSite JavaDoc is a little bit short on illustrating
>>>> how to use it together with class-loading.
>>>> The given example bootstrap Method:
>>>>
>>>> private static CallSite bootstrapDynamic(MethodHandles.Lookup caller,
>>>> String name, MethodType type) {
>>>>     // ignore caller and name, but match the type:
>>>>     return new ConstantCallSite(MethodHandles.collectArguments(printArgs, type));
>>>> }
>>>>
>>>> looks fine but this method is neither used nor linked or registered
>>>> in the sample code of the JavaDoc so here are my related questions:
>>>>
>>>> 1) What is needed in a bootstrap method to produce a working callSite
>>>> for a loaded class?
>>>>
>>>> 2) How is the bootstrap method linked to  an invokedynamic instruction?
>>>> The spec does not have the @BootstrapMethod anymore so what's the
>>>> current way of linking?
>>> The bootstrap method is know encoded as argument of the invokedynamic
>>> instruction.
>>> So each invokedynamic can have its own bootstrap method.
>>>
>>> The main problem is that there is no way currently to emit an
>>> invokedynamic in Java,
>>> see
>>> http://weblogs.java.net/blog/forax/archive/2011/01/07/call-invokedynamic-java
>>>
>>>> 3) Should the class-loading be done by the bootstrap method or  is it
>>>> fine to do it before?
>>> Fine to do it before.
>>>
>>>> I really appriciate any input, since I'm new to InvokeDynamics and not
>>>> familiar with all concepts.
>>>>
>>>> marvin
>>> Rémi
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