Java in a Nutshell, 5th Edition [Electronic resources] نسخه متنی

The static methods of this class
implement the default access-control mechanism as of Java 1.2.
checkPermission( ) traverses the call stack of the
current thread and checks whether all classes in the call stack have
the requested permission. If so, checkPermission(
) returns, and the operation can proceed. If not,
checkPermission( ) tHRows an
AccessControlException. As of Java 1.2, the
checkPermission( ) method of the default
java.lang.SecurityManager calls
AccessController.checkPermission( ). System-level
code that needs to perform an access check should invoke the
SecurityManager method rather than calling the
AccessController method directly. Unless you are
writing system-level code that must control access to system
resources, you never need to use this class or the
SecurityManager.checkPermission( ) method.

The various doPrivileged( ) methods run blocks of
privileged code encapsulated in a PrivilegedAction
or PrivilegedExceptionAction object. When
checkPermission( ) is traversing the call stack of
a thread, it stops if it reaches a privileged block that was executed
with doPrivileged( ). This means that privileged
code can run with a full set of privileges, even if it was invoked by
untrusted or lower-privileged code. See
PrivilegedAction for more details.

The getContext(
) method returns an AccessControlContext
that represents the current security context of the caller. Such a
context might be saved and passed to a future call (perhaps a call
made from a different thread). Use the two-argument version of
doPrivileged( ) to force permission checks to
check the AccessControlContext as well.

public final class

AccessController {
// No Constructor
// Public Class Methods
public static void

checkPermission (Permission

perm )
throws AccessControlException;
public static <T> T

doPrivileged (PrivilegedExceptionAction<T>

action )
throws PrivilegedActionException; naopdtive
public static <T> T

doPrivileged (PrivilegedAction<T>

action ); native
public static <T> T

doPrivileged (PrivilegedExceptionAction<T>

action ,
AccessControlContext

context )
throws PrivilegedActionException; native
public static <T> T

doPrivileged (PrivilegedAction<T>

action ,
AccessControlContext

context ); native
public static AccessControlContext

getContext ( );
}