Date:         Mon, 11 Jun 2007 04:16:48 -0700
Reply-To:     "Richard A. DeVenezia" <richard.google@DEVENEZIA.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "Richard A. DeVenezia" <richard.google@DEVENEZIA.COM>
Organization: http://groups.google.com
Subject:      Re: How to check, if a Java Class exists out of sas data step
Comments: To: sas-l@uga.edu
In-Reply-To:  <200706110904.l5B7bKbk020617@mailgw.cc.uga.edu>
Content-Type: text/plain; charset="us-ascii"

On Jun 11, 5:04 am, sasu...@CODE2BE.DE (Michael Weiss) wrote:
> Hello,
> I'm a bit new in SAS and have not as much knowledge about how to invoke java
> out of saa.
>
> To complain to our guidelines, I need to check if the class, I want to use
> is accessible or not.
>
> For that I would like to do something like:
>
> data checkClasses;
>  className='com/mypath/MyClass'; output;
>  className='com/mypath/MyClass2'; output;
> run;
>
> data checkResults(keep=className exists);
>
>  Declare javaObj class('java/lang/Class');
>  class.exceptionDescribe(1);
>  do until (last1);
>   set checkClasses end = last1;
>   class.callStaticVoidMethod('forName', className);
>   class.exceptionCheck(ex);
>   if ex eq 1 then do;
>    exists=0;
>    class.exceptionClear();
>   end; else do;
>    exists=1;
>   end;
>  end;
>  class.delete();
> run;
>
> Unfortunately I can't instantiate the Class java.lang.Class. Is there any
> way to access a static method of this class? Or is there any other way to
> check, if a class can be used? I need to catch the error, if it is not
> possible to use the class.

As you found out, javaobj can only instantiate a class that has a
public constructor.  Additionally, javaobj interact with a method that
returns an object.  Is there a reason you can not try to instantiate
MyClass directly ?

In general, to deal with any method that returns an object, you need
to write an adapter class that has a series of javaobj accessible
methods for interacting with a delegate.  Perhaps some future version
of SAS will have a fully realized javaobj (would require an update of
the Component Object technology that deals with object returns, in
particular, a javaobj implementation that accomodates all aspects of
JNI)