[GitHub] [netbeans] matthiasblaesing commented on pull request #4130: Invoke correct overload of ReferenceQueue::remove

[GitBox <gi...@apache.org>]

matthiasblaesing commented on PR #4130:
URL: https://github.com/apache/netbeans/pull/4130#issuecomment-1133322110

   I think we should stay away from the implementation details of the JDK. It _always_ comes back to haunt us. If I read the implementation correctly, the idea is, that only the implementation inside the Lookup API should be able to `remove` from the `ReferenceQueue`. So why not change the guard method (untested!):
   
   ```diff
   # This patch file was generated by NetBeans IDE
   # It uses platform neutral UTF-8 encoding and \n newlines.
   --- a/platform/openide.util.lookup/src/org/openide/util/lookup/implspi/ActiveQueue.java
   +++ b/platform/openide.util.lookup/src/org/openide/util/lookup/implspi/ActiveQueue.java
   @@ -48,6 +48,8 @@
    
        private static final class Impl extends ReferenceQueue<Object> {
            
   +        private ThreadLocal<Boolean> accessOk = new ThreadLocal<>();
   +
            Impl() {
            }
    
   @@ -58,18 +60,31 @@
    
            @Override
            public Reference<Object> remove(long timeout) throws IllegalArgumentException, InterruptedException {
   +            if(accessOk.get() != null && accessOk.get()) {
   +                return (Reference<Object>) super.remove(timeout);
   +            } else {
                throw new InterruptedException();
            }
   +        }
    
            @Override
            public Reference<Object> remove() throws InterruptedException {
   +            if(accessOk.get() != null && accessOk.get()) {
   +                return (Reference<Object>) super.remove();
   +            } else {
                throw new InterruptedException();
            }
   +        }
            
            final Reference<? extends Object> removeSuper() throws InterruptedException {
   -            return super.remove(0);
   +            accessOk.set(Boolean.TRUE);
   +            try {
   +                return super.remove();
   +            } finally {
   +                accessOk.set(Boolean.FALSE);
            }
        }
   +    }
    
        private static final class Daemon extends Thread {
            private static boolean initialized;
   
   ```
   
   The permitted callers can come though `removeSuper` and are cleared, while public callers will not get through the `accessOk`check. Another alternative would be to store the thread, that is working the reference queue and reject all calls not from that thread.
   


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