The "lockedObject" might be better named "lockableObject." That way it
makes no assumptions about its current state. Building on this, the class
might be called Lockable.
However, I also like the idea of calling the class Locker, as in a gym
locker. The idea is that it holds something important. Or (since Locker
also sounds like a verb form) maybe it could be called a LockBox. That
implies that it wraps something, which is what we want.
I may come up with better suggestions if I could see the class. It's not in
master, and I don't see it on any branch. Can you provide a link?
— Miguel Muñoz
On Fri, Jun 26, 2020 at 7:07 AM Gary Gregory <garydgreg...@gmail.com> wrote:
>
> Hi All:
>
> I know email is a challenging medium for code reviews, so please consider
> these comments coming from my best intentions, constructive and caring ;-)
> Also please excuse the meandering nature of this post.
>
> The new class org.apache.commons.lang3.concurrent.Locks.Lock needs better
> names IMO, not just the class name. There is already a JRE interface
called
> Lock so this class name is confusing (to me.)
>
> The Javadoc reads in part:
>
> * This class implements a wrapper for a locked (hidden) object, and
> * provides the means to access it. The basic idea, is that the user
> * code forsakes all references to the locked object, using only the
> * wrapper object, and the accessor methods
>
> But this is not the case, the object itself is not locked in
> the traditional sense with a monitor through a synchronized block, so we
> need to update the Javadoc as well.
>
> To me, this is more about executing blocks of code (through lambdas) which
> then get 'safe' (via locking) access to an underlying object. This tells
me
> the class is more about the functional interfaces than about a domain
> "Object", hence the name "Lock" is not the best. It's really more of a
> visitor where the visitation pattern is: Lock, Visit, Unlock.
> Instead, maybe:
> - StampledLockVisitor (more specific)
> - LockingVisitor (more general)
> - SafeObject (vague)
> - ObjectLocker (vague)
> - rejected: LockedObject since the object itself is not locked.
> - ?
>
> What is also confusing IMO is that the instance variable for the object is
> called "lockedObject" but the object is in fact NOT locked all the time.
So
> that needs to be renamed IMO:
> - object (the simplest)
> - subject
> - domain
> - target
> - ?
>
> In the same vein, the StampedLock is named "lock" which is also confusing
> since StampedLock does not implement Lock.
>
> Why can't the domain object be null, it's never used by the framework?
> Why this:
> if (t == lockedObject) {
> throw new IllegalStateException("The returned object
> is, in fact, the hidden object.");
> }
> ?
> This seems like an application specific constraint that has nothing to do
> with the framework.
>
> Now that I've considered the above, the API Locks.lock(O) is really
> misnamed, because it does not lock anything, it's a factory method.
>
> Stepping back even more, since there is only a static inner class in
Locks,
> and no-hint that alternative implementations for different kind of locks
> are possible, I would say we do not need Locks, all we need is what is now
> called Lock.
>
> It's not clear why some methods are protected, I would make those private.
> It's not like I can use or plugin a Lock, ReentrantReadWriteLock, a
> ReentrantLock, or any ReadWriteLock instead of a StampedLock. I would then
> make the current Lock class a standalone class which can then be used
later
> from a factory class (now Locks) where we can then fill in with different
> implementations.
>
> The Javadoc talks about a "hidden" object but it is not hidden since it is
> passed to all visitors!
>
> This test assumption is wrong:
>
> If our threads are running concurrently, then we expect to be
> faster
> than running one after the other.
>
> The VM or Java spec makes no such guarantee and the tests have no control
> over VM scheduling. There are cases where this will fail when under heavy
> load for example where the cost of additional threads becomes
overwhelming.
>
> Another item I am quite doubtful about is hiding checked exceptions by
> rethrowning them as unchecked. I'd consider this an anti-pattern. If I am
> using one of our "Failing" interfaces it is because I am expecting it to
> fail. Perhaps this could be made smoother by refactoring to pass in a
> lambda for an exception handler.
>
> I've crystallized my thoughts into code here as WIP (Javadoc needs work):
> https://github.com/apache/commons-lang/pull/559
>
> Not as important as the above:
> The example in the Javadoc uses logging as its domain subject, a "logging"
> API (PrintStream) which is not a good example IMO. Logging frameworks
> today like Log4j handle multi-threaded applications normally without
having
> developers meddle in it. Yes, I understand it's a simple example but I am
> hoping we can come up with something more realistic or useful.
>
> Thank you,
> Gary
