nl.talsmasoftware.context.threadlocal

Class AbstractThreadLocalContext<T>

java.lang.Object

nl.talsmasoftware.context.threadlocal.AbstractThreadLocalContext<T>

All Implemented Interfaces:

Closeable, AutoCloseable, Context<T>

public abstract class AbstractThreadLocalContext<T>
extends Object
implements Context<T>

Abstract base class that will maintain a shared, static ThreadLocal instance for each concrete subclass of this type. This threadlocal can be accessed by subclasses through the protected method: threadLocalInstanceOf(Class).

Author:

Sjoerd Talsma

Field Summary

Fields

Modifier and Type	Field and Description
protected Context<T>	parentContext The parent context that was active at the time this context was created (if any) or null in case there was no active context when this context was created.
protected T	value The actual value, so subclasses can still access it after the context has been closed, because the default getValue() implementation will return null in that case. Please be careful accessing the value after the context was closed: There is no pre-defined meaningful way to handle this situation, as this depends heavily on the desired features of the particular implementation.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractThreadLocalContext(T newValue) Instantiates a new context with the specified value.

Method Summary

Modifier and Type	Method and Description
void	close() Closes this context and in case this context is the active context, restores the active context to the (unclosed) parent context. If no unclosed parent context exists, the 'active context' is cleared.
protected static <T,CTX extends AbstractThreadLocalContext<T>> CTX	current(Class<? extends CTX> contextType)
T	getValue() Returns the value of this context instance, or null if it was already closed.
protected boolean	isClosed() Returns whether this context is closed or not.
protected static <T,CTX extends AbstractThreadLocalContext<T>> ThreadLocal<CTX>	threadLocalInstanceOf(Class<? extends CTX> contextType) Returns the shared, static ThreadLocal instance for the specified context type.
String	toString() Returns the classname of this context followed by "{closed}" if it has been closed already; otherwise the contained value by this context will be added.

Methods inherited from class java.lang.Object

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

Field Detail

parentContext

protected final Context<T> parentContext

The parent context that was active at the time this context was created (if any) or null in case there was no active context when this context was created.

value

protected final T value

The actual value, so subclasses can still access it after the context has been closed, because the default getValue() implementation will return null in that case.
Please be careful accessing the value after the context was closed: There is no pre-defined meaningful way to handle this situation, as this depends heavily on the desired features of the particular implementation.

Constructor Detail

AbstractThreadLocalContext

protected AbstractThreadLocalContext(T newValue)

Instantiates a new context with the specified value. The new context will be made the active context for the current thread.

Parameters:

newValue - The new value to become active in this new context (or null to register a new context with 'no value').

Method Detail

isClosed

protected boolean isClosed()

Returns whether this context is closed or not.

Returns:

Whether the context is already closed.

getValue

public T getValue()

Returns the value of this context instance, or null if it was already closed.

Specified by:

getValue in interface Context<T>

Returns:

The value of this context.

close

public void close()

Closes this context and in case this context is the active context, restores the active context to the (unclosed) parent context.
If no unclosed parent context exists, the 'active context' is cleared.

This method has no side-effects if the context was already closed (it is safe to call multiple times).

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Context<T>

toString

public String toString()

Returns the classname of this context followed by "{closed}" if it has been closed already; otherwise the contained value by this context will be added.

Overrides:

toString in class Object

Returns:

String representing this context class and either the current value or the fact that it was closed.

threadLocalInstanceOf

protected static <T,CTX extends AbstractThreadLocalContext<T>> ThreadLocal<CTX> threadLocalInstanceOf(Class<? extends CTX> contextType)

Returns the shared, static ThreadLocal instance for the specified context type.

Type Parameters:

T - The type being managed by the context.

CTX - The first non-abstract context subclass of AbstractThreadLocalContext.

Parameters:

contextType - The first concrete subclass of the abstract threadlocal context (So values from separate subclasses do not get mixed up).

Returns:

The non-null shared ThreadLocal instance to register these contexts on.

current

protected static <T,CTX extends AbstractThreadLocalContext<T>> CTX current(Class<? extends CTX> contextType)