Class InheritableThreadLocal<T>

java.lang.Object
java.lang.ThreadLocal<T>
java.lang.InheritableThreadLocal<T>
Type Parameters:
T - the type of the inheritable thread local's value
public class InheritableThreadLocal<T> extends ThreadLocal<T>
This class extends ThreadLocal to provide inheritance of values from parent thread to child thread: when a child thread is created, the child receives initial values for all inheritable thread-local variables for which the parent has values. Normally the child's values will be identical to the parent's; however, the child's value can be made an arbitrary function of the parent's by overriding the childValue method in this class.

Inheritable thread-local variables are used in preference to ordinary thread-local variables when the per-thread-attribute being maintained in the variable (e.g., User ID, Transaction ID) must be automatically transmitted to any child threads that are created.

Note: During the creation of a new thread, it is possible to opt out of receiving initial values for inheritable thread-local variables.

Since:
1.2
See Also:

  • Constructor Summary

    Constructors
    Constructor
    Description
    InheritableThreadLocal()
    Creates an inheritable thread local variable.

  • Method Summary

    Modifier and Type
    Method
    Description
    protected T
    childValue(T parentValue)
    Computes the child's initial value for this inheritable thread-local variable as a function of the parent's value at the time the child thread is created.

    Methods declared in class ThreadLocal

    get, initialValue, remove, set, withInitial
    Modifier and Type
    Method
    Description
    T
    get()
    Returns the value in the current thread's copy of this thread-local variable.
    protected T
    initialValue()
    Returns the current thread's "initial value" for this thread-local variable.
    void
    remove()
    Removes the current thread's value for this thread-local variable.
    void
    set(T value)
    Sets the current thread's copy of this thread-local variable to the specified value.
    static <S> ThreadLocal<S>
    withInitial(Supplier<? extends S> supplier)
    Creates a thread local variable.

    Methods declared in class Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    Modifier and Type
    Method
    Description
    protected Object
    clone()
    Creates and returns a copy of this object.
    boolean
    equals(Object obj)
    Indicates whether some other object is "equal to" this one.
    protected void
    finalize()
    Deprecated, for removal: This API element is subject to removal in a future version.
    Finalization is deprecated and subject to removal in a future release.
    final Class<?>
    getClass()
    Returns the runtime class of this Object.
    int
    hashCode()
    Returns a hash code value for this object.
    final void
    notify()
    Wakes up a single thread that is waiting on this object's monitor.
    final void
    notifyAll()
    Wakes up all threads that are waiting on this object's monitor.
    String
    toString()
    Returns a string representation of the object.
    final void
    wait()
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
    final void
    wait(long timeoutMillis)
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
    final void
    wait(long timeoutMillis, int nanos)
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

  • Constructor Details

    • InheritableThreadLocal

      public InheritableThreadLocal()
      Creates an inheritable thread local variable.

  • Method Details

    • childValue

      protected T childValue(T parentValue)
      Computes the child's initial value for this inheritable thread-local variable as a function of the parent's value at the time the child thread is created. This method is called from within the parent thread before the child is started.

      This method merely returns its input argument, and should be overridden if a different behavior is desired.

      Parameters:
      parentValue - the parent thread's value
      Returns:
      the child thread's initial value