AbstractContext.java

Go to the documentation of this file.

/*
 * 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.lang.Parallelizable;
import javolution.context.SecurityContext.Permission;
import javolution.lang.Realtime;
 
@Realtime
@Parallelizable(comment = "Sequential configuration, parallel use")
public abstract class AbstractContext {
 
    private static final ThreadLocal<AbstractContext> CURRENT = new ThreadLocal<AbstractContext>();
 
    private AbstractContext outer;
 
    protected AbstractContext() {}
 
    public static AbstractContext current() {
        return AbstractContext.CURRENT.get();
    }
 
    @SuppressWarnings("unchecked")
    protected static <T extends AbstractContext> T current(Class<T> type) {
        AbstractContext ctx = AbstractContext.CURRENT.get();
        while (ctx != null) {
            if (type.isInstance(ctx))
                return (T) ctx;
            ctx = ctx.outer;
        }
        return null;
    }
 
    @SuppressWarnings("unchecked")
    public static <T extends AbstractContext> T enter(Class<T> custom) {
        SecurityContext.check(new Permission<T>(custom, "enter"));
        try {
            return (T) custom.newInstance().enterInner();
        } catch (InstantiationException e) {
            throw new IllegalArgumentException(
                    "Cannot instantiate instance of " + custom, e);
        } catch (IllegalAccessException e) {
            throw new IllegalArgumentException("Cannot access " + custom, e);
        }
    }
 
    public static void inherit(AbstractContext ctx) {
        CURRENT.set(ctx);
    }
 
    protected AbstractContext enterInner() {
        AbstractContext inner = inner();
        inner.outer = AbstractContext.CURRENT.get();
        AbstractContext.CURRENT.set(inner);
        return inner;
    }
 
    public void exit() {
        if (this != AbstractContext.CURRENT.get())
            throw new IllegalStateException(
                    "This context is not the current context");
        AbstractContext.CURRENT.set(outer);
        outer = null;
    }
 
    protected AbstractContext getOuter() {
        return outer;
    }
 
    protected abstract AbstractContext inner();
 
}