sorry if I am asking a dumb question but why do you think the code base does not follow ISP?

You could send it as Authorization http header to angular

Thanks for your answer. But the whole process I have mentioned in my post is all about data sync between two systems and mostly synchronizing two systems and keeping the data upto date in both the databases

Thanks for your answer. But I did not get when you say '?Dynamically load the rule classes'. These rules are not in the same jar.As a example per my requirement, if I have two programs A and B, In A if the transaction amount is > 10000, then I need to send an email to some email address. And in program B if a file reader did not find any records then I need to send an email. So these are similar examples and rules I am talking about and they may be in different jars.