javolution.context

Class AbstractContext

java.lang.Object

javolution.context.AbstractContext

Direct Known Subclasses:

ConcurrentContext, FormatContext, LocalContext, LogContext, SecurityContext

@Realtime
@Parallelizable(comment="Sequential configuration, parallel use")
public abstract class AbstractContext
extends Object

The parent class for all contexts. Contexts allow for cross cutting concerns (performance, logging, security, ...) to be addressed at run-time through OSGi published services without polluting the application code ( Separation of Concerns).

Context configuration is performed in a try, finally block statement and impacts only the current thread (although inherited by inner ConcurrentContext threads).

 AnyContext ctx = AnyContext.enter(); // Enters a context scope. 
 try {                             
     ctx.configure(...); // Local configuration (optional).
     ... // Current thread executes using the configured context.
 } finally {
     ctx.exit(); 
 }

Version:

6.0, July 21, 2013

Author:

Jean-Marie Dautelle

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractContext() Default constructor.

Method Summary

Methods

Modifier and Type	Method and Description
static AbstractContext	current() Returns the current context for the current thread or null if this thread has no context (default).
protected static <T extends AbstractContext> T	current(Class<T> type) Returns the current context of specified type or null if none.
static <T extends AbstractContext> T	enter(Class<T> custom) Enters the scope of a custom context.
protected AbstractContext	enterInner() Enters the scope of an inner context which becomes the current context; the previous current context becomes the outer of this context.
void	exit() Exits the scope of this context; the outer of this context becomes the current context.
protected AbstractContext	getOuter() Returns the outer context of this context or null if this context has no outer context.
static void	inherit(AbstractContext ctx) Inherits the specified context which becomes the context of the current thread.
protected abstract AbstractContext	inner() Returns a new inner instance of this context inheriting the properties of this context.

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractContext

protected AbstractContext()

Default constructor.

Method Detail

current

public static AbstractContext current()

Returns the current context for the current thread or null if this thread has no context (default).

current

protected static <T extends AbstractContext> T current(Class<T> type)

Returns the current context of specified type or null if none.

enter

public static <T extends AbstractContext> T enter(Class<T> custom)

Enters the scope of a custom context. This method raises a SecurityException if the permission to enter contexts of the specified class is not granted. For example, the following disallow entering any custom context.

 SecurityContext ctx = SecurityContext.enter(); 
 try {
     ctx.revoke(new SecurityContext.Permission(AbstractContext.class, "enter"));
     ... // Cannot enter any custom context.
 } finally {
     ctx.exit(); // Back to previous security settings. 
 }

Parameters:

custom - the custom context to enter.

Throws:

IllegalArgumentException - if the specified class default constructor cannot be instantiated.

SecurityException - if SecurityContext.Permission(custom, "enter") is not granted.

See Also:

SecurityContext.Permission

inherit

public static void inherit(AbstractContext ctx)

Inherits the specified context which becomes the context of the current thread. This method is particularly useful when creating new threads to make them inherits from the context stack of the parent thread.

 //Spawns a new thread inheriting the context of the current thread.
 MyThread myThread = new MyThread();
 myThread.inherited = AbstractContext.current(); 
 myThread.start(); 
 ...
 class MyThread extends Thread {
     AbstractContext inherited;
     public void run() {
         AbstractContext.inherit(inherited); // Sets current context. 
         ...
     }
 }

enterInner

protected AbstractContext enterInner()

Enters the scope of an inner context which becomes the current context; the previous current context becomes the outer of this context.

Returns:

the inner context entered.

exit

public void exit()

Exits the scope of this context; the outer of this context becomes the current context.

Throws:

IllegalStateException - if this context is not the current context.

getOuter

protected AbstractContext getOuter()

Returns the outer context of this context or null if this context has no outer context.

inner

protected abstract AbstractContext inner()

Returns a new inner instance of this context inheriting the properties of this context. The new instance can be configured independently from its parent.