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 InheritableThreadLocals 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.
InheritableThreadLocal variables are used in preference to ordinary
ThreadLocal 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
- See Also:
ThreadLocal
Method Summary |
protected Object |
childValue(Object parentValue)
Computes the child's initial value for this InheritableThreadLocal
as a function of the parent's value at the time the child Thread is
created. |
Object |
get()
Returns the value in the calling thread's copy of this ThreadLocal
variable. |
void |
set(Object value)
Sets the calling thread's instance of this ThreadLocal variable
to the given value. |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
InheritableThreadLocal
public InheritableThreadLocal()
- Creates an InheritableThreadLocal variable.
get
public Object get()
- Returns the value in the calling thread's copy of this ThreadLocal
variable. Creates and initializes the copy if this is the first time
the thread has called this method.
- Overrides:
get
in class ThreadLocal
- Following copied from class:
java.lang.ThreadLocal
- Returns:
- the value of this ThreadLocal
set
public void set(Object value)
- Sets the calling thread's instance of this ThreadLocal variable
to the given value. This is only used to change the value from
the one assigned by the initialValue method, and many applications
will have no need for this functionality.
- Overrides:
set
in class ThreadLocal
- Parameters:
value
- the value to be stored in the calling threads' copy of
this ThreadLocal.
childValue
protected Object childValue(Object parentValue)
- Computes the child's initial value for this InheritableThreadLocal
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
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