Operator Overloading Problem

development python
1

Hi all,

I’m trying to use SNAPPY to do some mosaicking, but I keep running into the same error that leads me to believe there is an issue in jpy when overloading the operators.

The mosaic operator expects a list of products (Product[] sourceProducts;), yet I get this error:
RuntimeError: java.lang.ClassCastException: class [Lorg.esa.snap.core.datamodel.Product; cannot be cast to class org.esa.snap.core.datamodel.Product ([Lorg.esa.snap.core.datamodel.Product; and org.esa.snap.core.datamodel.Product are in unnamed module of loader 'app')

It seems like it’s trying to convert the Product[] to a Product even though the function itself expects a Product[].

I’m using SNAP 11.0 on W11 in Python 3.10. Code snippet below.

from esa_snappy import jpy, HashMap

def Mosaic(sourceProducts):
    ProductArray = jpy.array('org.esa.snap.core.datamodel.Product', len(sourceProducts))

    for i, p in enumerate(sourceProducts):
        ProductArray[i] = p

    params = HashMap()
    product = HashMap()
    product.put("sourceProducts", ProductArray)

    return esa_snappy.GPF.createProduct("Mosaic", params, product)
2

You can either pass the ProductArray directly as the sourceProducts argument (see GPF.java, line 217), or use a HashMap<String, Product> as the sourceProducts argument (see GPF.java, line 284).

3

As shown above, passing a HashMap returns an error.

Passing ProductArray directly returns RuntimeError: org.esa.snap.core.gpf.OperatorException, showing that the signature is not recognized.

4

Put every product as an item of the HashMap. You can then drop the ProductArray .

productMap = HashMap()
for i, p in enumerate(sourceProducts):
    productMap.put(f"sourceProduct_{i}", p)

or use ProductMap directly

return esa_snappy.GPF.createProduct("Mosaic", params, ProductArray)
5

Using productMap directly also gives an OperatorException.
Passing it as a HashMap gives RuntimeError: java.lang.ClassCastException: class java.util.HashMap cannot be cast to class org.esa.snap.core.datamodel.Product (java.util.HashMap is in module java.base of loader 'bootstrap'; org.esa.snap.core.datamodel.Product is in unnamed module of loader 'app')
And here again, it’s trying to convert to a Product, not a Product[], which is the root cause of the problem.

It seems to me like the operator overloading is not properly handled by JPY.

6

Okay, looks like this. Someone should look at this more closely. Maybe @dolaf can do this, or @TomBlock