Class Finalizer

java.lang.Object
com.google.common.base.internal.Finalizer
All Implemented Interfaces:
Runnable

public class Finalizer extends Object implements Runnable
Thread that finalizes referents. All references should implement com.google.common.base.FinalizableReference.

While this class is public, we consider it to be *internal* and not part of our published API. It is public so we can access it reflectively across class loaders in secure environments.

This class can't depend on other Guava code. If we were to load this class in the same class loader as the rest of Guava, this thread would keep an indirect strong reference to the class loader and prevent it from being garbage collected. This poses a problem for environments where you want to throw away the class loader. For example, dynamically reloading a web application or unloading an OSGi bundle.

com.google.common.base.FinalizableReferenceQueue loads this class in its own class loader. That way, this class doesn't prevent the main class loader from getting garbage collected, and this class can detect when the main class loader has been garbage collected and stop itself.

  • Field Details

    • logger

      private static final Logger logger
    • FINALIZABLE_REFERENCE

      private static final String FINALIZABLE_REFERENCE
      Name of FinalizableReference.class.
      See Also:
    • finalizableReferenceClassReference

      private final WeakReference<Class<?>> finalizableReferenceClassReference
    • frqReference

      private final PhantomReference<Object> frqReference
    • queue

      private final ReferenceQueue<Object> queue
    • bigThreadConstructor

      private static final Constructor<Thread> bigThreadConstructor
    • inheritableThreadLocals

      private static final Field inheritableThreadLocals
  • Constructor Details

  • Method Details

    • startFinalizer

      public static void startFinalizer(Class<?> finalizableReferenceClass, ReferenceQueue<Object> queue, PhantomReference<Object> frqReference)
      Starts the Finalizer thread. FinalizableReferenceQueue calls this method reflectively.
      Parameters:
      finalizableReferenceClass - FinalizableReference.class.
      queue - a reference queue that the thread will poll.
      frqReference - a phantom reference to the FinalizableReferenceQueue, which will be queued either when the FinalizableReferenceQueue is no longer referenced anywhere, or when its close() method is called.
    • run

      public void run()
      Loops continuously, pulling references off the queue and cleaning them up.
      Specified by:
      run in interface Runnable
    • cleanUp

      private boolean cleanUp(Reference<?> reference)
      Cleans up a single reference. Catches and logs all throwables.
      Returns:
      true if the caller should continue, false if the associated FinalizableReferenceQueue is no longer referenced.
    • getFinalizeReferentMethod

      private Method getFinalizeReferentMethod()
      Looks up FinalizableReference.finalizeReferent() method.
    • getInheritableThreadLocalsField

      private static Field getInheritableThreadLocalsField()
    • getBigThreadConstructor

      private static Constructor<Thread> getBigThreadConstructor()