java.lang: public class: InheritableThreadLocal

java.lang
public class: InheritableThreadLocal [javadoc | source]

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

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.

Also see:

ThreadLocal

author: Josh - Bloch and Doug Lea

since: 1.2 -

Method from java.lang.InheritableThreadLocal Summary:
childValue, createMap, getMap

Methods from java.lang.ThreadLocal:
childValue, createInheritedMap, createMap, get, getMap, initialValue, remove, set

Methods from java.lang.Object:
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method from java.lang.InheritableThreadLocal Detail:
protected T childValue(T parentValue) { return 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.
void createMap(Thread t, T firstValue) { t.inheritableThreadLocals = new ThreadLocalMap(this, firstValue); } Create the map associated with a ThreadLocal.
ThreadLocalMap getMap(Thread t) { return t.inheritableThreadLocals; } Get the map associated with a ThreadLocal.

Method from java.lang.InheritableThreadLocal Detail:

 protected T childValue(T parentValue) {
        return parentValue;
}

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

  void createMap(Thread t,
    T firstValue) {
        t.inheritableThreadLocals = new ThreadLocalMap(this, firstValue);
}

Create the map associated with a ThreadLocal.

 ThreadLocalMap getMap(Thread t) {
       return t.inheritableThreadLocals;
}

Get the map associated with a ThreadLocal.