[Jython-dev] Conversion of Data Types in Jython's BSF Engine

[Don S. <don...@gm...>]

Hello,
 
The current implementation of JythonEngine seems to be very selective
about when to "unwrap" Python objects and return pure Java objects.
The return value from call() is always unwrapped (and input arguments
are wrapped appropriately).  However, the return values from eval()
and apply() are only unwrapped if the code returns a PyJavaInstance
(i.e., not for PyString, PyInteger, etc.).
 
This means that if a client of BSF wants to allow the user to use both
Ruby and Python code, they must write some Python-specific Java code
in order to extract the return values from Jython wrapper objects.
Since the goal of BSF is to provide a language-independent abstraction
layer which allows the user to switch languages at will, requiring
them to import Jython-specific packages is obviously a bad thing.
 
I've attached a patch that makes Jython's BSFEngine behave more like
the other languages.  I've CC'd the jython-dev list as I suspect they may
have some input on this (with respect to backwards compatibility issues,
etc.).
 
How does everyone feel about this?
 
Thanks,
Don
 
Index: src/org/apache/bsf/engines/jython/JythonEngine.java
===================================================================
RCS file: /home/cvspublic/jakarta-bsf/src/org/apache/bsf/engines/jython/JythonEngine.java,v
retrieving revision 1.8
diff -u -r1.8 JythonEngine.java
--- src/org/apache/bsf/engines/jython/JythonEngine.java 14 Jun 2004
17:29:40 -0000      1.8
+++ src/org/apache/bsf/engines/jython/JythonEngine.java 15 Jan 2005
23:23:28 -0000
@@ -145,8 +145,8 @@
             
           Object result = interp.eval ("bsf_temp_fn()");
             
-          if (result != null && result instanceof PyJavaInstance)
-              result = ((PyJavaInstance)result).__tojava__(Object.class);
+          if (result != null && result instanceof PyObject)
+              result = unwrap((PyObject)result);
           return result;
       } catch (PyException e) {
           throw new BSFException (BSFException.REASON_EXECUTION_ERROR,
@@ -161,8 +161,8 @@
                      Object script) throws BSFException {
        try {
          Object result = interp.eval (byteify(script.toString ()));
-         if (result != null && result instanceof PyJavaInstance)
-               result = ((PyJavaInstance)result).__tojava__(Object.class);
+         if (result != null && result instanceof PyObject)
+               result = unwrap((PyObject)result);
          return result;
        } catch (PyException e) {
          throw new BSFException (BSFException.REASON_EXECUTION_ERROR,