Re: [Jython-users] Compiling jython subclassing java classes

[Samuele P. <pe...@in...>]

From: Chris Atkins <Chr...@al...>
> I have a jython class which derives from junit.framework.TestCase, a java
> class.  I noticed several odd behaviors with jythonc while trying to get a
> compiled jython class I could call from java.  Following is my final code
> which works:
> 
> Following is the modified code which does:
> # file JTest.py
> import junit
> 
> from money import *
> 
> class JTest(junit.framework.TestCase):
>  def __init__(self, name):
>    self.name = name
> #   junit.framework.TestCase.__init__(self, name)
> 
>  def testSimpleAdd(self):
>    "@sig public void testSimpleAdd()"
>    print "Executing testSimpleAdd"
>    m12CHF = Money(12, "CHF")
>    m14CHF = Money(14, "CHF")
>    expected = Money(26, "CHF")
>    result = m12CHF.add(m14CHF)
>    junit.framework.Assert.assertEquals(expected, result)
> 
> Following is the output of jythonc on the above
> processing JTest
> 
> Required packages:
>   money*
>   junit.framework
> 
> Creating adapters:
> 
> Creating .java files:
>   JTest module
>     JTest extends junit.framework.TestCase
> 
> 1)When the the call to the TestCase.__init__(self, name) method is
> uncommented, and I try to use the code with the following java code:
> import JTest;
> import junit.framework.*;
> 
> public class Tester2 {
> 
>   public Tester2() {}
> 
>   public static void main(String[] args) {
>     JTest t = new JTest("testSimpleAdd");
>     t.testEquals();
>     TestSuite s = new TestSuite(JTest.class);
>     TestResult result = new TestResult();
>     s.run(result);
>     System.out.println("Ran " + result.runCount() + " Failed: " +
> result.failureCount() + " Errors: " + result.errorCount());
>   }
> }
> 
> I get the following error:
> Exception in thread "main" Java Traceback:
> 
> at org.python.core.Py.TypeError(Py.java:120)
> at
> org.python.core.PyReflectedConstructor.__call__(PyReflectedConstructor.java:
> 88)
> at
> org.python.core.PyReflectedConstructor.__call__(PyReflectedConstructor.java:
> 72)
> at
> org.python.core.PyReflectedConstructor.__call__(PyReflectedConstructor.java:
> 162)
> at org.python.core.PyObject.__call__(PyObject.java:285)
> at JTest$_PyInner.__init__$1(JTest.java:70)
> at JTest$_PyInner.call_function(JTest.java:54)
> at org.python.core.PyTableCode.call(PyTableCode.java:155)
> at org.python.core.PyTableCode.call(PyTableCode.java:353)
> at org.python.core.PyTableCode.call(PyTableCode.java:258)
> at org.python.core.PyFunction.__call__(PyFunction.java:110)
> at org.python.core.PyInstance.__init__(PyInstance.java:161)
> at org.python.core.Py.initProxy(Py.java:751)
> at JTest.<init>(JTest.java:167)
> at Tester2.main(Tester2.java:9)
> Traceback (innermost last):
>   File "/homes/atkicd/junit/mytests/money/JTest.py", line 0, in __init__
> TypeError: instance already instantiated for junit.framework.TestCase
> 
> I do not understand this or see why I am getting this, I should be able to
> call a specific subclass constructor from the __init__ method of my python
> class.
> 
> 1a)With the modification in 1) above, I could not compile my jython class
> because the generated code was making a call to the no argument constructor
> for TestCase() which happens to be non public.  javac would therefore not
> compile the generated java code.  I do not have any calls to
> junit.framework.TestCase() in my code and do not understand why jythonc put
> one in the generated java code.  (I modified the TestCase() constructor to
> be public).
> 
> 2)If I do not use the full class names for the java items,
> junit.framework.TestCase, but instead use the minimum name based on my
> import statements as in
> import junit.framework.TestCase
> and in the jython code use TestCase, my generated code for the jython class
> inherits from java.lang.Object instead of TestCase.
> 
> Following is the modified original class:
> # file JTest.py
> import junit.framework.TestCase
> import junit.framework.Assert
> 
> from money import *
> 
> class JTest(TestCase):
>  def __init__(self, name):
>    self.name = name
>    TestCase.__init__(self, name)
> 
>  def testSimpleAdd(self):
>    "@sig public void testSimpleAdd()"
>    print "Executing testSimpleAdd"
>    m12CHF = Money(12, "CHF")
>    m14CHF = Money(14, "CHF")
>    expected = Money(26, "CHF")
>    result = m12CHF.add(m14CHF)
>    Assert.assertEquals(expected, result)
> 
> Following is the output of running jythonc:
> processing JTest
> 
> Required packages:
>   junit.framework
>   money*
> 
> Creating adapters:
> 
> Creating .java files:
>   JTest module
> 
> 
> This code would run in jython, but gets compiled improperly.  This sure
> seems like a bug.
> 

no jythonc and jython interpeter have slightly different semantics,

jythonc emits in the constructor a super that calls the supeclass
constructor with the same signature,

From jython side (jython interpreter) you construct a Python class
that lazily construct a proxy class (the truly java subclassing class) 
instance either when you call the super class constructor, or at the
end of the Python __init__.

From java side with a jythonc-ed class you directly construct the proxy
that setups the Python instance, we could add more policy control
but you cannot have the flexibility of the other case.

regards.