javolution.context

Class LocalContext

java.lang.Object

javolution.context.AbstractContext

javolution.context.LocalContext

public abstract class LocalContext
extends AbstractContext

A context holding locally scoped parameters values.

For example, when performing modulo arithmetics the actual modulo being used is usually the same for most operations and does not need to be specified for each operation.

 import javolution.context.LocalContext.Parameter;
 public class ModuloInteger extends Number {
     public static final Parameter<Integer> MODULO = new Parameter<Integer>() {
          protected Integer getDefault() { return -1; }
     }; 
     public ModuloInteger times(ModuloInteger that) { ... }    
 }     
 LocalContext ctx = LocalContext.enter(); 
 try {
     ctx.supersede(ModuloInteger.MODULO, 13); // Sets local modulo value.
     x = a.times(b).plus(c.times(d)); // Operations modulo 13
     ...
 } finally {
     ctx.exit(); // Reverts to previous modulo setting. 
 }

As for any context, local context settings are inherited during ConcurrentContext executions.

Version:

6.0 December 12, 2012

Author:

Jean-Marie Dautelle

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	LocalContext.Parameter<T> A configurable parameter whose value can be locally superseded within the scope of LocalContext.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	LocalContext() Default constructor.

Method Summary

Methods

Modifier and Type	Method and Description
static LocalContext	enter() Enters and returns a new local context instance.
protected abstract <T> T	getValue(LocalContext.Parameter<T> param, T defaultValue) Returns the local value of the specified parameter or the specified default value if not superseded.
abstract <T> void	supersede(LocalContext.Parameter<T> param, T localValue) Supersedes the value of the specified parameter.

Methods inherited from class javolution.context.AbstractContext

current, current, enter, enterInner, exit, getOuter, inherit, inner

Methods inherited from class java.lang.Object

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

Constructor Detail

LocalContext

protected LocalContext()

Default constructor.

Method Detail

enter

public static LocalContext enter()

Enters and returns a new local context instance.

supersede

public abstract <T> void supersede(LocalContext.Parameter<T> param,
                 T localValue)

Supersedes the value of the specified parameter.

Parameters:

param - the local parameter whose local value is overridden.

localValue - the new local value.

Throws:

SecurityException - if the permission to override the specified parameter is not granted.

NullPointerException - if the specified local value is null.

getValue

protected abstract <T> T getValue(LocalContext.Parameter<T> param,
             T defaultValue)

Returns the local value of the specified parameter or the specified default value if not superseded.

Parameters:

param - the local parameter whose local value is returned.

defaultValue - the parameter value if not superseded.