Java. How to intercept an argument when calling a method?

Question

Java

There is a singleton object from third-party code, you need to intercept the argument when calling its method.
Or as an alternative, override the method in this object.
Is there such a possibility at all?

Answer 1

Your case is rather difficult, but do not forget that reflection is capable of miracles .
PS In python, this (anti-pattern) is called monkey patching.

Answer 2

If you use JavaEE, then you can intercept method calls from EJB beans through an annotation in which you point to the interceptor class. More details here , for example.

Answer 3

If you call the singleton methods, then you can create a duplicate class that will repeat the singleton interface and redirect calls to it + log the passed parameters.
To override methods, one could use the CGLIB library, which can create a class proxy, but since this is a singleton, it is most likely the final class without a public constructor, Java will not allow such an override.
In general, no way.