[Solved] Recover Orekit types from python bindings returning java primitive types

Orekit Python Wrapper usage
1

This seems to be an occurrence with methods that return iterable types. My specific example is utilizing FieldOfView.getFootprint()

The return type is java.util.List[java.util.List[org.orekit.bodies.GeodeticPoint]] so it returns a list of lists of points. When accessing the sublist inside the main list, the return is a java Object class and only methods native to that base class are available.

object = footprint_raw.get(0)
print(type(object))
print(object.getClass())

<class 'java.lang.Object'>
class java.util.ArrayList

This is easy enough to recover from by creating a new instance from the object because an ArrayList can be initialized from another Array List

shape = java.util.ArrayList(object)

Now we have shape which is a list of GeodeticPoint but when trying to access a point the return type is once again just the Object base class

point = shape.get(0)
print(point)
print(type(point))
print(point.getClass())

{lat: 9.9077704309 deg, lon: 61.472804441 deg, alt: 0}
<class 'java.lang.Object'>
class org.orekit.bodies.GeodeticPoint

None of the methods from GeodeticPoint are available when using Python, only base Object methods are. For example:

point.getLatitude()

results in

point.getLatitude()
    ^^^^^^^^^^^^^^^^^
AttributeError: 'Object' object has no attribute 'getLatitude'

Is there a way to get an actual GeodeticPoint instance without calling .toString() and parsing out the values to initialize new instances? That would work in a bind for a simple class like this but would not be feasible for other classes who need more complex variable types in their __init__().

One thing I did try was point.clone() to see what type gets returned but even though it’s a method of the Object class it is not implemented and fails.

In short how do I get access to the methods of an implemented class in Python when it thinks my object is Object even though it is implementing an actual Orekit class

Thanks in advance!

2

Should’ve done a better job searching for threads before posting. Pretty simple solution pointed out here: Access getFootprint data - #3 by spaceman

Even used the exact same functionality I was trying to deal with!

from java.util import List
...
footprint = fieldOfView.getFootprint(...)
footprint = list(footprint)
footprint = [list(List.cast_(points)) for points in footprint]
for points in footprint:
        for point in points:
                point = GeodeticPoint.cast_(point)

Thank you @Vincent !!!

3

Great that you found the solution for the Orekit jcc wrapper.

But FYI when using the new Orekit jpype wrapper there is no need for casting, you get directly GeodeticPoint objects instead of Object objects IIRC.

4

I was already planning to switch over but now there is all the more reason to. Thanks for the info