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()
    Answers a new instance of the same class as the receiver, whose slots have been filled in with the values in the slots of the receiver.
    boolean
    equals(Object o)
    Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
    protected void
    finalize()
    Deprecated, for removal: This API element is subject to removal in a future version.
    May cause performance issues, deadlocks and hangs.
    final Class<? extends Object>
    getClass()
    Answers the unique instance of java.lang.Class which represents the class of the receiver.
    int
    hashCode()
    Answers an integer hash code for the receiver.
    final void
    notify()
    Causes one thread which is waiting on the receiver to be made ready to run.
    final void
    notifyAll()
    Causes all threads which are waiting on the receiver to be made ready to run.
    String
    toString()
    Answers a string containing a concise, human-readable description of the receiver.
    final void
    wait()
    Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by notify or notifyAll).
    final void
    wait(long time)
    Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.
    final void
    wait(long time, int frac)
    Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.

  • 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