util/concurrent/PrivilegedFutureTask.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain. Use, modify, and
 * redistribute this code in any way without acknowledgement.
 */

package java.util.concurrent;

import java.security.AccessControlContext;
import java.security.AccessControlException;
import java.security.AccessController;
import java.security.PrivilegedAction;

/**
 * A {@link FutureTask} that executes, if allowed, with the current
 * access control context and context class loader of the thread
 * creating the task. A new <tt>PrivilegedFutureTask</tt> 
 * can be created within an {@link AccessController#doPrivileged}
 * action to run tasks under the selected permission settings
 * holding within that action.
 * @see Executors
 *
 * @since 1.5
 * @author Doug Lea
 */
public class PrivilegedFutureTask<T> extends FutureTask<T> {
    private final ClassLoader ccl;
    private final AccessControlContext acc;

    /**
     * Constructs a <tt>PrivilegedFutureTask</tt> that will, upon running,
     * execute the given <tt>Callable</tt> under the current access control 
     * context, with the current context class loader as the context class 
     * loader.
     *
     * @throws AccessControlException if the current access control context 
     *         does not have permission to both set and get context class loader.
     */
    public PrivilegedFutureTask(Callable<T> task) {
        super(task);
        this.ccl = Thread.currentThread().getContextClassLoader();
        this.acc = AccessController.getContext();
        acc.checkPermission(new RuntimePermission("getContextClassLoader"));
        acc.checkPermission(new RuntimePermission("setContextClassLoader"));
    }

    /**
     * Executes within the established access control and context
     * class loader if possible, else causes invocations of {@link
     * Future#get} to receive the associated AccessControlException.
     */
    public void run() {
        try {
            AccessController.doPrivileged(new PrivilegedFutureAction(), acc);
        } catch(Throwable ex) {
            setException(ex);
        }
    }

    private class PrivilegedFutureAction implements PrivilegedAction {
        public Object run() {
            ClassLoader saved = null;
            try {
                ClassLoader current = Thread.currentThread().getContextClassLoader();
                if (ccl != current) {
                    Thread.currentThread().setContextClassLoader(ccl);
                    saved = current;
                }
                PrivilegedFutureTask.super.run();
                return null;
            } finally {
                if (saved != null)
                    Thread.currentThread().setContextClassLoader(saved);
            }
        }
    }
}
Revision:	1.4
Committed:	Sat Dec 20 14:00:05 2003 UTC (20 years, 5 months ago) by dl
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.3:	+0 -0 lines
State:	*FILE REMOVED*
Log Message:	Replace PrivilegedFutureTask with Executors.privilegedCallable
#	Content
1	/*
2	* Written by Doug Lea with assistance from members of JCP JSR-166
3	* Expert Group and released to the public domain. Use, modify, and
4	* redistribute this code in any way without acknowledgement.
5	*/
6
7	package java.util.concurrent;
8
9	import java.security.AccessControlContext;
10	import java.security.AccessControlException;
11	import java.security.AccessController;
12	import java.security.PrivilegedAction;
13
14	/**
15	* A {@link FutureTask} that executes, if allowed, with the current
16	* access control context and context class loader of the thread
17	* creating the task. A new <tt>PrivilegedFutureTask</tt>
18	* can be created within an {@link AccessController#doPrivileged}
19	* action to run tasks under the selected permission settings
20	* holding within that action.
21	* @see Executors
22	*
23	* @since 1.5
24	* @author Doug Lea
25	*/
26	public class PrivilegedFutureTask<T> extends FutureTask<T> {
27	private final ClassLoader ccl;
28	private final AccessControlContext acc;
29
30	/**
31	* Constructs a <tt>PrivilegedFutureTask</tt> that will, upon running,
32	* execute the given <tt>Callable</tt> under the current access control
33	* context, with the current context class loader as the context class
34	* loader.
35	*
36	* @throws AccessControlException if the current access control context
37	* does not have permission to both set and get context class loader.
38	*/
39	public PrivilegedFutureTask(Callable<T> task) {
40	super(task);
41	this.ccl = Thread.currentThread().getContextClassLoader();
42	this.acc = AccessController.getContext();
43	acc.checkPermission(new RuntimePermission("getContextClassLoader"));
44	acc.checkPermission(new RuntimePermission("setContextClassLoader"));
45	}
46
47	/**
48	* Executes within the established access control and context
49	* class loader if possible, else causes invocations of {@link
50	* Future#get} to receive the associated AccessControlException.
51	*/
52	public void run() {
53	try {
54	AccessController.doPrivileged(new PrivilegedFutureAction(), acc);
55	} catch(Throwable ex) {
56	setException(ex);
57	}
58	}
59
60	private class PrivilegedFutureAction implements PrivilegedAction {
61	public Object run() {
62	ClassLoader saved = null;
63	try {
64	ClassLoader current = Thread.currentThread().getContextClassLoader();
65	if (ccl != current) {
66	Thread.currentThread().setContextClassLoader(ccl);
67	saved = current;
68	}
69	PrivilegedFutureTask.super.run();
70	return null;
71	} finally {
72	if (saved != null)
73	Thread.currentThread().setContextClassLoader(saved);
74	}
75	}
76	}
77	}