Online payment (java payment framework)? Solutions, maybe free?

Question

Java

Hello,
there is a desire to deal with online payment and transactions.
Perhaps there are less or more or more or less free libraries for this? So that, for example, from one library it was possible to process transactions, for example, when paying with a credit card and PayPal?
And in general, how it works, where to read. I can’t google anything sensible.
Yes, of course, I will look at the PayPal developers page and read it, I just want to know if there is something "several in one".
Thank you.

Answer 1

I haven't seen any "all-in-one" libraries, but there are such services, for example, Yandex.Checkout. Simple API and a wide range of payment options. Naturally, there is a margin.