JEP 411: Deprecation with removal would break most existing Java libraries

[Alan Bateman]

cc'ing security-dev as that is the mailing list to use for this JEP.

This JEP is the first of several in a multi-release/multi-year effort. 
It's way too early to give any guess as to when the APIs will be 
removed. As the JEP says, future releases may degrade the SM APIs so 
that System.getSM returns always returns null or 
AccessController::doPriv just runs the action. This should mean that 
libraries that are compiling to older releases should continue to 
compile and run on those releases. When they run on some future release 
that degrades the implementation then it will be as if there is no SM.  
So I would say the impact is little to none for libraries for the 
foreseeable future.

-Alan


On 13/06/2021 21:28, Rafael Winterhalter wrote:
> I am currently looking into how I should address JEP 411 in my library Byte
> Buddy and I find it rather challenging. The problem I am facing is that I
> know of several users who rely on the security manager in their Java 8/11
> applications. I would like to continue to support those users' use cases as
> long as I support Java versions that contain the security manager, which
> will be for many years to come. At the same time, I would like to address
> the announced removal of the API and make sure that Byte Buddy can work
> without it prior to the deadline when the library in its current state
> would no longer link.
>
>  From my understanding of the intention of JEP 411, the API was supposed to
> be stubbed – similar to Android’s stubbing of the API - rather than being
> removed. However, with the announced deprecation for removal of
> AccessController and SecurityManager, I understand that I would need to
> fully remove the dispatching to work with future Java versions.
>
> Furthermore, it is difficult to create a working facade for dispatching to
> the security manager only if it is available. Methods like
> AccessController.doPrivileged are caller sensitive and by adding a utility
> to a library, this utility would leak to any potential user. It would
> therefore require package-private dispatchers for any relevant package,
> which would lead to a lot of copy-paste to retain backwards compatibility
> (given that a library cannot assume to be run as a module).
>
> Finally, removing the API would mean that Byte Buddy versions of the last
> ten years would no longer link in future JDKs. For Byte Buddy where new
> Java versions often require an update, that might not be a big issue but
> many other libraries do support the API, I don’t feel it would be a rather
> severe restriction and cause unnecessary breakage if API is removed, rather
> than stubbed. I am thinking of libraries like Netty here which are rather
> omnipresent and would suddenly no longer link, a concept that is unlikely
> intuitive to a lot of developers.
>
> Therefore, my question is: should SecurityManager, AccessController and the
> Policy APIs really be deprecated for removal? Rather, I think that the APIs
> should be deprecated, but be retained with stubbed implementations.
> System.getSecurityMananger would then always return null.
> System.setSecurityManager on the other hand could be deprecated for
> removal. This way, existing code could continue to work as if the security
> manager is not active, which already is the common scenario and would not
> cause any disruption at the small price of keeping a handful of some
> stubbed classes.
>
> Thanks for advice on how this is intended to be handled by library
> developers like me.
> Best regards, Rafael