@GuardedBy annotation with java.util.concurrent.locks.ReadWriteLock

Question

What is a proper/preferred way to annotate fields that are protected with a ReadWriteLock so that tools like FindBugs can leverage the annotation? Should the name of the ReadWriteLock simply be written in the @GuardedBy annotation. Is there ever a reason to write the name of just the read lock, or just the write lock, in the @GuardedBy annotation? Does FindBugs, or other tools, even support ReadWriteLock in @GuardedBy?

Answer 1

At the time of this writing, @GuardedBy isn't fully implemented by Findbugs, and is mostly just for documentation. (It is partially implemented.)

I always use @GuardedBy("readwritelock") or the object that I use to synchronize.

For example of the latter:

class Example {
    private Object lock = new Object();

    @GuardedBy("lock")
    private Stuff innards = ...;

    public void work() {
        synchronized(lock) {
            workWith(innards.goop());
        }
    }        
}

Answer 2

Find bugs supports the following annotations:

net.jcip.annotations.GuardedBy
net.jcip.annotations.Immutable
net.jcip.annotations.NotThreadSafe
net.jcip.annotations.ThreadSafe

Usage of these GuardedBy annotation should be as follows:

@ThreadSafe  
public class Queue<E> implements java.util.Queue<E>  
{  
    private ConcurrentLinkedQueue readWriteLock;  

    @GuardedBy( value="readWriteLock" )  
    public boolean offer(E o)  
    {  
        return queue.offer( o ); 
    }  

}