java.lang.InheritableThreadLocal Maven / Gradle / Ivy
/*
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This work corresponds to the API signatures of JSR 219: Foundation
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JSR 219 specification, which is available at
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*/
package java.lang;
import java.lang.ref.*;
/**
* 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.
*
* @author Josh Bloch and Doug Lea
* @version 1.17, 03/12/05
* @see ThreadLocal
* @since 1.2
*/
public class InheritableThreadLocal extends java.lang.ThreadLocal
{
public InheritableThreadLocal() { }
/**
* 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.
*
* @param parentValue the parent thread's value
* @return the child thread's initial value
*/
protected java.lang.Object childValue(java.lang.Object parentValue) {
return null;
}
}