LocalContext.java

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/*
 * Javolution - Java(TM) Solution for Real-Time and Embedded Systems
 * Copyright (C) 2012 - Javolution (http://javolution.org/)
 * All rights reserved.
 * 
 * Permission to use, copy, modify, and distribute this software is
 * freely granted, provided that this notice is preserved.
 */
package javolution.context;
 
import javolution.context.SecurityContext.Permission;
import javolution.lang.Configurable;
import javolution.osgi.internal.OSGiServices;
 
public abstract class LocalContext extends AbstractContext {
 
    public static abstract class Parameter<T> extends Configurable<T> {
 
        public static final Permission<Parameter<?>> SUPERSEDE_PERMISSION = new Permission<Parameter<?>>(
                Parameter.class, "supersede");
 
        private final Permission<Parameter<T>> supersedePermission;
 
        public Parameter() {
            this.supersedePermission = new Permission<Parameter<T>>(
                    Parameter.class, "supersede", this);
        }
 
        public Permission<Parameter<T>> getSupersedePermission() {
            return supersedePermission;
        }
 
        public T get() {
            LocalContext ctx = current(LocalContext.class);
            return (ctx != null) ? ctx.getValue(this, super.get()) : super.get();
        }
    }
 
    protected LocalContext() {}
 
    public static LocalContext enter() {
        LocalContext ctx = current(LocalContext.class);
        if (ctx == null) { // Root.
            ctx = OSGiServices.getLocalContext();
        }
        return (LocalContext) ctx.enterInner();
    }
 
    public abstract <T> void supersede(Parameter<T> param, T localValue);
 
    protected abstract <T> T getValue(Parameter<T> param, T defaultValue);
    
}