Defining method overload,JavaMultipleMethod, after autoclass

[ismailsimsek]

is it possible define overloaded methods, after autoclass?

MyClass = autoclass('io.MyClass')
# ensure both overloaded methods are recognised
MyClass.myMethod =  JavaMultipleMethod([
        '(Lio/Class1;)Lio/Builder',
        '(Lio/Class2;)Lio/Builder'
    ])

im passing and python implementation of an interface(io/Class2) but its not given to the right method.
it takes it as a io/Class1

[ismailsimsek]

ok did it like below. got it working.

MyClass = autoclass('io.MyClass')
MyClass.myMethod =  JavaMethod('(Lio/Class2;)Lio/Builder'')

now calls to myMethod are using second of the overloaded method.

[cmacdonald]

It might be good to have a test case if you think there is indeed a problem. there is some method selection code that tries to do the right thing...

Isnt this a case of just casting the object to the correct type? pyjnius.cast("Lio.Class1", obj)?

Or is this a problem with static methods?

[ismailsimsek]

@cmacdonald its a fairly complex usage. AFAIK not related to casting or static method

in this PR you could see full code, commented the fix.

@cmacdonald im worried about the correct usage of pyjnius . especially around the garbage collected classes and usage of proxy class. not sure if this code follows all the practices. If you have time, could you do a review of the code? will appreciate your review.

[cmacdonald]

You have two notifying methods in DebeziumEngine$Builder.
If the code is calling the wrong one, you can use the signature= kwarg to specify the one you do want. See example at https://github.com/terrier-org/pyterrier/blob/master/pyterrier/java/_core.py#L147-L149

I'm confused about your code - you are overriding the notifying method with one from a different class. If its because the actual calling code is ending up calling DebeziumEngine$Builder.notifying() rather than DebeziumEngine$ChangeConsumer.notifying(), then you should try also casting to DebeziumEngine$ChangeConsumer first?

[ismailsimsek]

You have two notifying methods in DebeziumEngine$Builder. If the code is calling the wrong one, you can use the signature= kwarg to specify the one you do want. See example at https://github.com/terrier-org/pyterrier/blob/master/pyterrier/java/_core.py#L147-L149

exactly this is the case. i will check the example

I'm confused about your code - you are overriding the notifying method with one from a different class. If its because the actual calling code is ending up calling DebeziumEngine$Builder.notifying()

this is correct, however DebeziumEngine$Builder.notifying() has two notifying() methods with different signatures

• first one: the one called without any fix.
  DebeziumEngine$Builder.notifying(Consumer<R> consumer)
• second one: the desired one. proxy class is implementing ChangeConsumer therefor this method should be the one getting called. when the proxy class is given as an argument.
  DebeziumEngine$Builder.notifying(ChangeConsumer<R> handler)

---

Edit:
the call flow is like below:
io.debezium.engine.DebeziumEngine creates io.debezium.engine.DebeziumEngine$Builder
then it calls io.debezium.engine.DebeziumEngine$Builder.notifying(ChangeConsumer handler) to set the handler variable.

[cmacdonald]

So I think you want something like:

builder = pt.autoclass("my.class")() # remember to construct the instance from the class
builder.notifying(handler, signature="(Lcom/mine/ChangeConsumer;)V")

More details:

JavaMultipleMethod calls calculate_score() to decide which method to invoke. Exact matches score highly; the assignability of an object to the class of an argument is not considered:

pyjnius/jnius/jnius_utils.pxi

Lines 390 to 402 in 17563c6

	# if we pass a JavaClass, ensure the definition is matching
	# XXX FIXME what if we use a subclass or something ?
	if isinstance(arg, JavaClass):
	jc = arg
	if jc.__javaclass__ == r:
	score += 10
	else:
	#try:
	# check_assignable_from(jc, r)
	#except:
	# return -1
	score += 5
	continue

In short, the calculate_score() is a series of heuristics, trying to reimplement Java rules while inexactly matching to Python types at the same time.

Specify the signature simply tells jnius which method you want.

PS: Perhaps a PR for the documentation that tells people about signature kwarg?