com.pega.pegarules.bootstrap.util

Class VicariousThreadLocal<T>

java.lang.Object

java.lang.ThreadLocal<T>

com.pega.pegarules.bootstrap.util.VicariousThreadLocal<T>

Type Parameters:

T -

public class VicariousThreadLocal<T>
extends java.lang.ThreadLocal<T>

A drop-in replacement ThreadLocal implementation that does not leak when thread-local values reference the ThreadLocal object. The code is optimised to cope with frequently changing values.

In comparison to plain ThreadLocal, this implementation:

• from the point of view of a single thread, each thread-local {code #get} requires access to four objects instead of two
• is fractionally slower in terms of CPU cycles for {code #get}
• uses around twice the memory for each thead-local value
• uses around four times the memory for each ThreadLocal
• may release thread-local values for garbage collection more promptly

See: http://jroller.com/page/tackline?entry=working_around_the_threadlocal_leak

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	VERSION

Constructor Summary

Constructors

Constructor and Description
VicariousThreadLocal() Creates a new VicariousThreadLocal.

Method Summary

Modifier and Type	Method and Description
<R> R	callWith(T value, java.util.concurrent.Callable<R> doCall) Executes task with thread-local set to the specified value.
T	get()
boolean	isInitialized() Indicates whether thread-local has been initialised for the current thread.
static <T> VicariousThreadLocal<T>	newThreadLocal() Creates a new VicariousThreadLocal.
static <T> VicariousThreadLocal<T>	newThreadLocal(java.util.concurrent.Callable<T> doCall) Creates a new VicariousThreadLocal with initial value from Callable.
static <T> VicariousThreadLocal<T>	newThreadLocal(T initialValue) Creates a new VicariousThreadLocal with specified initial value.
void	poll() Check if any strong references need should be removed due to thread exit.
void	remove()
void	runWith(T value, java.lang.Runnable doRun) Executes task with thread-local set to the specified value.
void	set(T value)
T	swap(T value) Swaps the current threads value with the supplied value.

Methods inherited from class java.lang.ThreadLocal

withInitial

Methods inherited from class java.lang.Object

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

Field Detail

VERSION

public static final java.lang.String VERSION

Constructor Detail

VicariousThreadLocal

public VicariousThreadLocal()

Creates a new VicariousThreadLocal.

Method Detail

newThreadLocal

public static <T> VicariousThreadLocal<T> newThreadLocal()

Creates a new VicariousThreadLocal.

Returns:

T

newThreadLocal

public static <T> VicariousThreadLocal<T> newThreadLocal(T initialValue)

Creates a new VicariousThreadLocal with specified initial value.

Parameters:

initialValue -

Returns:

T

newThreadLocal

public static <T> VicariousThreadLocal<T> newThreadLocal(java.util.concurrent.Callable<T> doCall)

Creates a new VicariousThreadLocal with initial value from Callable.

Parameters:

doCall -

Returns:

T

get

public T get()

Overrides:

get in class java.lang.ThreadLocal<T>

set

public void set(T value)

Overrides:

set in class java.lang.ThreadLocal<T>

remove

public void remove()

Overrides:

remove in class java.lang.ThreadLocal<T>

isInitialized

public boolean isInitialized()

Indicates whether thread-local has been initialised for the current thread.

Returns:

boolean

swap

public T swap(T value)

Swaps the current threads value with the supplied value. Thread-local will be initialised if not already done so.

Parameters:

value -

Returns:

T

runWith

public void runWith(T value,
                    java.lang.Runnable doRun)

Executes task with thread-local set to the specified value. The state is restored however the task exits. If uninitialised before running the task, it will remain so upon exiting. Setting the thread-local within the task does not affect the state after exitign.

Parameters:

value -

doRun -

callWith

public <R> R callWith(T value,
                      java.util.concurrent.Callable<R> doCall)
               throws java.lang.Exception

Executes task with thread-local set to the specified value. The state is restored however the task exits. If uninitialised before running the task, it will remain so upon exiting. Setting the thread-local within the task does not affect the state after exitign.

Parameters:

value -

doCall -

Returns:

value returned by doCall

Throws:

java.lang.Exception

poll

public void poll()

Check if any strong references need should be removed due to thread exit.