java.lang
Class InheritableThreadLocal

java.lang.Object
  java.lang.ThreadLocal
      java.lang.InheritableThreadLocal

public class InheritableThreadLocal

extends ThreadLocal

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.

Since:

1.2

Author:

Josh Bloch and Doug Lea

See Also:

ThreadLocal

Nested Class Summary

Nested classes inherited from class java.lang.ThreadLocal

ThreadLocal.ThreadLocalMap

Field Summary

Fields inherited from class java.lang.ThreadLocal

Constructor Summary

InheritableThreadLocal()

Method Summary

protected Object	childValue(Object 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.
(package private) void	createMap(Thread t, Object firstValue) Create the map associated with a ThreadLocal.
(package private) ThreadLocal.ThreadLocalMap	getMap(Thread t) Get the map associated with a ThreadLocal.

Methods inherited from class java.lang.ThreadLocal

createInheritedMap, get, initialValue, set

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

InheritableThreadLocal

public InheritableThreadLocal()

Method Detail

childValue

protected Object childValue(Object 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.

Overrides:

childValue in class ThreadLocal

Parameters:

parentValue - the parent thread's value

Returns:

the child thread's initial value

getMap

ThreadLocal.ThreadLocalMap getMap(Thread t)

Get the map associated with a ThreadLocal.

Overrides:

getMap in class ThreadLocal

Parameters:

t - the current thread

Returns:

the map

createMap

void createMap(Thread t,
               Object firstValue)

Create the map associated with a ThreadLocal.

Overrides:

createMap in class ThreadLocal

Parameters:

t - the current thread

firstValue - value for the initial entry of the table.