java.lang
Class InheritableThreadLocal

java.lang.Object
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 +--java.lang.ThreadLocal
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 +--java.lang.InheritableThreadLocal

public class InheritableThreadLocal

extends ThreadLocal

Untamed: 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

Version:

1.15, 12/03/01

Author:

Josh Bloch and Doug Lea

See Also:

ThreadLocal

InheritableThreadLocal

public InheritableThreadLocal()

Enabled:

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

java.lang.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.