io.netty.util.concurrent

Class FastThreadLocal<V>

java.lang.Object

io.netty.util.concurrent.FastThreadLocal<V>

Type Parameters:

V - the type of the thread-local variable

public class FastThreadLocal<V>
extends Object

A special variant of ThreadLocal that yields higher access performance when accessed from a FastThreadLocalThread.

Internally, a FastThreadLocal uses a constant index in an array, instead of using hash code and hash table, to look for a variable. Although seemingly very subtle, it yields slight performance advantage over using a hash table, and it is useful when accessed frequently.

To take advantage of this thread-local variable, your thread must be a FastThreadLocalThread or its subtype. By default, all threads created by DefaultThreadFactory are FastThreadLocalThread due to this reason.

Note that the fast path is only possible on threads that extend FastThreadLocalThread, because it requires a special field to store the necessary state. An access by any other kind of thread falls back to a regular ThreadLocal.

See Also:

ThreadLocal

Constructor Summary

Constructors

Constructor and Description
FastThreadLocal()

Method Summary

Modifier and Type	Method and Description
static void	destroy() Destroys the data structure that keeps all FastThreadLocal variables accessed from non-FastThreadLocalThreads.
V	get() Returns the current value for the current thread
V	get(InternalThreadLocalMap threadLocalMap) Returns the current value for the specified thread local map.
V	getIfExists() Returns the current value for the current thread if it exists, null otherwise.
protected V	initialValue() Returns the initial value for this thread-local variable.
boolean	isSet() Returns true if and only if this thread-local variable is set.
boolean	isSet(InternalThreadLocalMap threadLocalMap) Returns true if and only if this thread-local variable is set.
protected void	onRemoval(V value) Invoked when this thread local variable is removed by remove().
void	remove() Sets the value to uninitialized for the specified thread local map.
void	remove(InternalThreadLocalMap threadLocalMap) Sets the value to uninitialized for the specified thread local map.
static void	removeAll() Removes all FastThreadLocal variables bound to the current thread.
void	set(InternalThreadLocalMap threadLocalMap, V value) Set the value for the specified thread local map.
void	set(V value) Set the value for the current thread.
static int	size() Returns the number of thread local variables bound to the current thread.

Methods inherited from class java.lang.Object

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

Constructor Detail

FastThreadLocal

public FastThreadLocal()

Method Detail

removeAll

public static void removeAll()

Removes all FastThreadLocal variables bound to the current thread. This operation is useful when you are in a container environment, and you don't want to leave the thread local variables in the threads you do not manage.

size

public static int size()

Returns the number of thread local variables bound to the current thread.

destroy

public static void destroy()

Destroys the data structure that keeps all FastThreadLocal variables accessed from non-FastThreadLocalThreads. This operation is useful when you are in a container environment, and you do not want to leave the thread local variables in the threads you do not manage. Call this method when your application is being unloaded from the container.

get

public final V get()

Returns the current value for the current thread

getIfExists

public final V getIfExists()

Returns the current value for the current thread if it exists, null otherwise.

get

public final V get(InternalThreadLocalMap threadLocalMap)

Returns the current value for the specified thread local map. The specified thread local map must be for the current thread.

set

public final void set(V value)

Set the value for the current thread.

set

public final void set(InternalThreadLocalMap threadLocalMap,
                      V value)

Set the value for the specified thread local map. The specified thread local map must be for the current thread.

isSet

public final boolean isSet()

Returns true if and only if this thread-local variable is set.

isSet

public final boolean isSet(InternalThreadLocalMap threadLocalMap)

Returns true if and only if this thread-local variable is set. The specified thread local map must be for the current thread.

remove

public final void remove()

Sets the value to uninitialized for the specified thread local map. After this, any subsequent call to get() will trigger a new call to initialValue().

remove

public final void remove(InternalThreadLocalMap threadLocalMap)

Sets the value to uninitialized for the specified thread local map. After this, any subsequent call to get() will trigger a new call to initialValue(). The specified thread local map must be for the current thread.

initialValue

protected V initialValue()
                  throws Exception

Returns the initial value for this thread-local variable.

Throws:

Exception

onRemoval

protected void onRemoval(V value)
                  throws Exception

Invoked when this thread local variable is removed by remove(). Be aware that remove() is not guaranteed to be called when the `Thread` completes which means you can not depend on this for cleanup of the resources in the case of `Thread` completion.

Throws:

Exception