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/*
* Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.security;
/**
* A {@code DomainCombiner} provides a means to dynamically
* update the ProtectionDomains associated with the current
* {@code AccessControlContext}.
*
* <p> A {@code DomainCombiner} is passed as a parameter to the
* appropriate constructor for {@code AccessControlContext}.
* The newly constructed context is then passed to the
* {@code AccessController.doPrivileged(..., context)} method
* to bind the provided context (and associated {@code DomainCombiner})
* with the current execution Thread. Subsequent calls to
* {@code AccessController.getContext} or
* {@code AccessController.checkPermission}
* cause the {@code DomainCombiner.combine} to get invoked.
*
* <p> The combine method takes two arguments. The first argument represents
* an array of ProtectionDomains from the current execution Thread,
* since the most recent call to {@code AccessController.doPrivileged}.
* If no call to doPrivileged was made, then the first argument will contain
* all the ProtectionDomains from the current execution Thread.
* The second argument represents an array of inherited ProtectionDomains,
* which may be {@code null}. ProtectionDomains may be inherited
* from a parent Thread, or from a privileged context. If no call to
* doPrivileged was made, then the second argument will contain the
* ProtectionDomains inherited from the parent Thread. If one or more calls
* to doPrivileged were made, and the most recent call was to
* doPrivileged(action, context), then the second argument will contain the
* ProtectionDomains from the privileged context. If the most recent call
* was to doPrivileged(action), then there is no privileged context,
* and the second argument will be {@code null}.
*
* <p> The {@code combine} method investigates the two input arrays
* of ProtectionDomains and returns a single array containing the updated
* ProtectionDomains. In the simplest case, the {@code combine}
* method merges the two stacks into one. In more complex cases,
* the {@code combine} method returns a modified
* stack of ProtectionDomains. The modification may have added new
* ProtectionDomains, removed certain ProtectionDomains, or simply
* updated existing ProtectionDomains. Re-ordering and other optimizations
* to the ProtectionDomains are also permitted. Typically the
* {@code combine} method bases its updates on the information
* encapsulated in the {@code DomainCombiner}.
*
* <p> After the {@code AccessController.getContext} method
* receives the combined stack of ProtectionDomains back from
* the {@code DomainCombiner}, it returns a new
* AccessControlContext that has both the combined ProtectionDomains
* as well as the {@code DomainCombiner}.
*
* @see AccessController
* @see AccessControlContext
* @since 1.3
*/
public interface DomainCombiner {
/**
* Modify or update the provided ProtectionDomains.
* ProtectionDomains may be added to or removed from the given
* ProtectionDomains. The ProtectionDomains may be re-ordered.
* Individual ProtectionDomains may be modified (with a new
* set of Permissions, for example).
*
* <p>
*
* @param currentDomains the ProtectionDomains associated with the
* current execution Thread, up to the most recent
* privileged {@code ProtectionDomain}.
* The ProtectionDomains are are listed in order of execution,
* with the most recently executing {@code ProtectionDomain}
* residing at the beginning of the array. This parameter may
* be {@code null} if the current execution Thread
* has no associated ProtectionDomains.<p>
*
* @param assignedDomains an array of inherited ProtectionDomains.
* ProtectionDomains may be inherited from a parent Thread,
* or from a privileged {@code AccessControlContext}.
* This parameter may be {@code null}
* if there are no inherited ProtectionDomains.
*
* @return a new array consisting of the updated ProtectionDomains,
* or {@code null}.
*/
ProtectionDomain[] combine(ProtectionDomain[] currentDomains,
ProtectionDomain[] assignedDomains);
}