SecurityContext.java

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/*
 * Javolution - Java(TM) Solution for Real-Time and Embedded Systems
 * Copyright (C) 2007 - 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.osgi.internal.OSGiServices;
 
public abstract class SecurityContext extends AbstractContext {
 
    public static class Permission<T> {
 
        public static final Permission<Object> ALL = new Permission<Object>(
                null);
 
        private final Class<? super T> category;
 
        private final String action;
 
        private final T instance;
 
        public Permission(Class<? super T> category) {
            this(category, null, null);
        }
 
        public Permission(Class<? super T> category, String action) {
            this(category, action, null);
        }
 
        public Permission(Class<? super T> category, String action, T instance) {
            this.category = category;
            this.action = action;
            this.instance = instance;
        }
 
        public Class<? super T> getCategory() {
            return category;
        }
 
        public String getAction() {
            return action;
        }
 
        public T getInstance() {
            return instance;
        }
 
        public boolean implies(Permission<?> that) {
            if (category == null)
                return true;
            if (!category.isAssignableFrom(that.category))
                return false;
            if (action == null)
                return true;
            if (!action.equals(that.action))
                return false;
            if (instance == null)
                return true;
            if (!instance.equals(that.instance))
                return false;
            return true;
        }
 
        @Override
        public String toString() {
            if (category == null)
                return "All permissions";
            if (action == null)
                return "Permission for any action on " + category.getName();
            if (instance == null)
                return "Permission for " + action + " on " + category.getName();
            return "Permission for " + action + " on instance " + instance
                    + " of " + category.getName();
        }
 
        @Override
        public boolean equals(Object obj) {
            if (obj == this)
                return true;
            if (!(obj instanceof Permission))
                return false;
            Permission<?> that = (Permission<?>) obj;
            if ((category == null) && (that.category != null))
                return false;
            if ((category != null) && (!category.equals(that.category)))
                return false;
            if ((action == null) && (that.action != null))
                return false;
            if ((action != null) && (!action.equals(that.action)))
                return false;
            if ((instance == null) && (that.instance != null))
                return false;
            if ((instance != null) && (!instance.equals(that.instance)))
                return false;
            return false;
        }
 
        @Override
        public int hashCode() {
            return (category != null ? category.hashCode() : 0)
                    + (action != null ? action.hashCode() : 0)
                    + (instance != null ? instance.hashCode() : 0);
        }
    }
 
    protected SecurityContext() {}
 
    public static SecurityContext enter() {
        return (SecurityContext) currentSecurityContext().enterInner();
    }
 
    public static void check(Permission<?> permission) {
        if (!currentSecurityContext().isGranted(permission))
            throw new SecurityException(permission + " is not granted.");
    }
 
    public abstract boolean isGranted(Permission<?> permission);
 
    public abstract void grant(Permission<?> permission, Object certificate);
 
    public abstract void revoke(Permission<?> permission, Object certificate);
 
    public final void grant(Permission<?> permission) {
        grant(permission, null);
    }
 
    public final void revoke(Permission<?> permission) {
        revoke(permission, null);
    }
 
    private static SecurityContext currentSecurityContext() {
        SecurityContext ctx = current(SecurityContext.class);
        if (ctx != null)
            return ctx;
        return OSGiServices.getSecurityContext();
    }
}