The risk of the new one or the risk of keeping the old 100K lines? Half serious question since I would estimate the risk of the latter to be much larger.
To me it sounds like he was introducing a hard dependency on AspectJ, which is as much a risk as any other dependency. I am guessing here, bit it is a scenario where a hissy fit from management has at least some justification.
It is just as much of a liability, a priori neither more nor less. It needs to be evaluated like any other potential new dependency.
Plus, AspectJ is something that you have to be careful with. It injects code at the start or end of methods that can do arbitraty things and the method source code doesn't indicate that this is happening. So it has a great potential for code obfuscation.
Sort of unrelated rant. Maybe it’s because I’m not as well versed in Java idioms as I am with C# idioms, but using code that implements AOP using AspectJ seems much more obtuse than what I’ve done in C# just looking at the examples.
In C#, with the various frameworks - including on the API level with ASP.Net - you can use attributes to decorate the classes/methods with your aspects and it’s pretty easy to see what it’s doing.
You get the runtime binding basically by just using dependency injection as you always do.
C# dev here as well, but from a Java background. When I first moved to C# from Java one of the best AOP usages was transaction management. Database transaction management. You could write all of the code, whether it was dependent upon the db or not, and then decorate the methods with a transaction attribute. This decoration contained all the logic to get a db connection, begin a transaction, become part of an existing one, or create a new isolated one. Any unhandled exception caused the final unwinding to rollback any work that had been done in that transaction. So many try/catch/finally's avoided and so much boilerplate code.
I have yet to find any equivalent to this .NET world. Especially of you're using EF. Either you use ADO and have your try/catch/finally with manual transaction management, or you have the EF context which is just one big blob you hope succeeds at the end.