Reduce overhead of the security manager

[retronym]

Continues the work started in #11 by systematically overriding
all the other methods of SecurityManager for a fast path when
the base security manager is null.

Fixes #134

[retronym]

In practice, overriding checkRead / checkWrite / checkDelete / checkExec would likely be enough, if you're prefer a targetted version to the blanket approach I've taken here.

[jvican]

LGTM

[retronym]

@sbalabanov How does this approach look?

[JoshRosen]

Should this be base.checkRead() instead of super.checkRead()? I have the same question for the new overloads added in this PR. It looks like @qma asked the same question on the original patch: #11 (comment)

[JoshRosen]

On reflection, I suspect that this was done for backwards-compatibility reasons, since overriding and delegating to base would be a behavior change whereas this change is only a performance optimization.

[retronym]

super.checkRead will eventually get to base.checkPermission. But it would be potentially more efficient to call base.checkRead directly here. The semantics should be the same for any well behaved SecurityManager.

[retronym]

I've pushed a commit that delegates directly to the corresponding method.

[unkarjedy]

Note that SecurityManager is deprecated since Java 17 and will be removed in future releases:
https://openjdk.java.net/jeps/411

To move the Java Platform forward, we will deprecate the legacy Security Manager technology for removal from the JDK. We plan to deprecate and attenuate the capabilities of the Security Manager over a number of releases, simultaneously creating alternative APIs for such tasks as blocking System::exit and other use cases considered important enough to have replacements.

Currently, NailgunServer produces a warning in stderr:

WARNING: A terminally deprecated method in java.lang.System has been called
WARNING: System::setSecurityManager has been called by %s
WARNING: Please consider reporting this to the maintainers of %s
WARNING: System::setSecurityManager will be removed in a future release