I'm trying to do something similar to Question 4617364 but for Python - load a class from python script file, where said class implements a Java interface and hand it over to some Java code that can use its methods - but calls to the object method return invalid values and printing from the initializer doesn't seem to do anything.
My implementation looks like this:
Interface:
package some.package;
import java.util.List;
public interface ScriptDemoIf {
int fibonacci(int d);
List<String> filterLength(List<String> source, int maxlen);
}
Python Implementation:
from some.package import ScriptDemoIf
class ScriptDemo(ScriptDemoIf):
""" Class ScriptDemo implementing ScriptDemoIf """
def __init__(self):
print "Script Demo init"
def fibonacci(self, d):
if d < 2:
return d
else:
return self.fibonacci(d-1) + self.fibonacci(d-2)
def filterLength(self, source, maxlen):
return [ str for str in source if len(str) <= maxlen ]
Class loader:
public ScriptDemoIf load(String filename) throws ScriptException {
ScriptEngine engine = new ScriptEngineManager().getEngineByName("jython");
FileReader script = new FileReader(filename);
try {
engine.eval(new FileReader(script));
} catch (FileNotFoundException e) {
throw new ScriptException("Failed to load " + filename);
}
return (ScriptDemoIf) engine.eval("ScriptDemo()");
}
public void run() {
ScriptDemoIf test = load("ScriptDemo.py");
System.out.println(test.fibonacci(30));
}
(Obviously the loader is a bit more generic in real life - it doesn't assume that the implementation class name is "ScriptDemo" - this is just for simplicity).
When the code is being ran, I don't see the print from the Python's __init__ (though if I put a print in the body of the script then I do see that), but the test variable in run() look like a valid jython "proxy object" and I get no casting errors. When I try to run the fibonacci() method I always get 0 (even if I change the method to always return a fixed number) and the filterLength() method always returns null (probably something to do with defaults according to the Java interface).
what am I doing wrong?
