Bug 50238

This occurs under logging with serialized LoggerEvent as 
SimpleSocketServe does.

For example 

Multi processed socket clients send logs to SocketServer, and server 
reads serialized LoggingEvents with o.a.l.s.LoggingEvent#readObject(), 
this calls internally o.a.l.s.LoggingEvent#readLevel(ObjectInputStream) 
which uses thead-unsafe `static final` variable. (see below at line 439)

This results in inconsistent log levels.


I reproduced with 4-processes socket clients, each client has 10-threads, 
toward single-process SimpleSocketServer. Clients sent 80,000 logs in 
all, and about 10 of them were wrong leveled.

[LoggingEvent.java]

142:  static final Integer[] PARAM_ARRAY = new Integer[1];

...

417:  private
418:  void readLevel(ObjectInputStream ois)
419:                      throws java.io.IOException, ClassNotFoundException {
420:
421:    int p = ois.readInt();
422:    try {
423:      String className = (String) ois.readObject();
424:      if(className == null) {
425:        level = Level.toLevel(p);
426:      } else {
427:        Method m = (Method) methodCache.get(className);
428:        if(m == null) {
429:          Class clazz = Loader.loadClass(className);
430:          // Note that we use Class.getDeclaredMethod instead of
431:          // Class.getMethod. This assumes that the Level subclass
432:          // implements the toLevel(int) method which is a
433:          // requirement. Actually, it does not make sense for Level
434:          // subclasses NOT to implement this method. Also note that
435:          // only Level can be subclassed and not Priority.
436:          m = clazz.getDeclaredMethod(TO_LEVEL, TO_LEVEL_PARAMS);
437:          methodCache.put(className, m);
438:        }
439:        PARAM_ARRAY[0] = new Integer(p);  // <=== !!! thread-unsafe !!!
440:        level = (Level) m.invoke(null,  PARAM_ARRAY);
441:      }
442:    } catch(InvocationTargetException e) {
443:        if (e.getTargetException() instanceof InterruptedException
444:                || e.getTargetException() instanceof InterruptedIOException) {
445:            Thread.currentThread().interrupt();
446:        }
447:    LogLog.warn("Level deserialization failed, reverting to default.", e);
448:        level = Level.toLevel(p);
449:    } catch(NoSuchMethodException e) {
450:        LogLog.warn("Level deserialization failed, reverting to default.", e);
451:        level = Level.toLevel(p);
452:    } catch(IllegalAccessException e) {
453:        LogLog.warn("Level deserialization failed, reverting to default.", e);
454:        level = Level.toLevel(p);
455:    } catch(RuntimeException e) {
456:        LogLog.warn("Level deserialization failed, reverting to default.", e);
457:        level = Level.toLevel(p);
458:    }
459:  }