/* |
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* Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. Oracle designates this |
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* particular file as subject to the "Classpath" exception as provided |
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* by Oracle in the LICENSE file that accompanied this code. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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*/ |
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package java.security.acl; |
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import java.util.Enumeration; |
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import java.security.Principal; |
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/** |
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* Interface representing an Access Control List (ACL). An Access |
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* Control List is a data structure used to guard access to |
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* resources.<p> |
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* |
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* An ACL can be thought of as a data structure with multiple ACL |
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* entries. Each ACL entry, of interface type AclEntry, contains a |
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* set of permissions associated with a particular principal. (A |
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* principal represents an entity such as an individual user or a |
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* group). Additionally, each ACL entry is specified as being either |
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* positive or negative. If positive, the permissions are to be |
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* granted to the associated principal. If negative, the permissions |
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* are to be denied.<p> |
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* |
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* The ACL Entries in each ACL observe the following rules: |
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* |
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* <ul> <li>Each principal can have at most one positive ACL entry and |
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* one negative entry; that is, multiple positive or negative ACL |
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* entries are not allowed for any principal. Each entry specifies |
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* the set of permissions that are to be granted (if positive) or |
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* denied (if negative). |
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* |
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* <li>If there is no entry for a particular principal, then the |
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* principal is considered to have a null (empty) permission set. |
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* |
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* <li>If there is a positive entry that grants a principal a |
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* particular permission, and a negative entry that denies the |
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* principal the same permission, the result is as though the |
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* permission was never granted or denied. |
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* |
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* <li>Individual permissions always override permissions of the |
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* group(s) to which the individual belongs. That is, individual |
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* negative permissions (specific denial of permissions) override the |
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* groups' positive permissions. And individual positive permissions |
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* override the groups' negative permissions. |
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* |
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* </ul> |
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* |
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* The {@code java.security.acl } package provides the |
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* interfaces to the ACL and related data structures (ACL entries, |
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* groups, permissions, etc.), and the {@code sun.security.acl } |
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* classes provide a default implementation of the interfaces. For |
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* example, {@code java.security.acl.Acl } provides the |
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* interface to an ACL and the {@code sun.security.acl.AclImpl } |
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* class provides the default implementation of the interface.<p> |
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* |
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* The {@code java.security.acl.Acl } interface extends the |
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* {@code java.security.acl.Owner } interface. The Owner |
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* interface is used to maintain a list of owners for each ACL. Only |
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* owners are allowed to modify an ACL. For example, only an owner can |
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* call the ACL's {@code addEntry} method to add a new ACL entry |
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* to the ACL. |
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* |
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* @see java.security.acl.AclEntry |
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* @see java.security.acl.Owner |
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* @see java.security.acl.Acl#getPermissions |
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* |
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* @author Satish Dharmaraj |
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*/ |
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public interface Acl extends Owner { |
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/** |
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* Sets the name of this ACL. |
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* |
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* @param caller the principal invoking this method. It must be an |
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* owner of this ACL. |
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* |
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* @param name the name to be given to this ACL. |
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* |
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* @exception NotOwnerException if the caller principal |
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* is not an owner of this ACL. |
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* |
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* @see #getName |
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*/ |
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public void setName(Principal caller, String name) |
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throws NotOwnerException; |
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/** |
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* Returns the name of this ACL. |
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* |
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* @return the name of this ACL. |
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* |
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* @see #setName |
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*/ |
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public String getName(); |
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/** |
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* Adds an ACL entry to this ACL. An entry associates a principal |
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* (e.g., an individual or a group) with a set of |
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* permissions. Each principal can have at most one positive ACL |
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* entry (specifying permissions to be granted to the principal) |
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* and one negative ACL entry (specifying permissions to be |
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* denied). If there is already an ACL entry of the same type |
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* (negative or positive) already in the ACL, false is returned. |
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* |
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* @param caller the principal invoking this method. It must be an |
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* owner of this ACL. |
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* |
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* @param entry the ACL entry to be added to this ACL. |
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* |
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* @return true on success, false if an entry of the same type |
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* (positive or negative) for the same principal is already |
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* present in this ACL. |
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* |
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* @exception NotOwnerException if the caller principal |
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* is not an owner of this ACL. |
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*/ |
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public boolean addEntry(Principal caller, AclEntry entry) |
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throws NotOwnerException; |
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/** |
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* Removes an ACL entry from this ACL. |
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* |
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* @param caller the principal invoking this method. It must be an |
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* owner of this ACL. |
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* |
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* @param entry the ACL entry to be removed from this ACL. |
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* |
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* @return true on success, false if the entry is not part of this ACL. |
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* |
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* @exception NotOwnerException if the caller principal is not |
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* an owner of this Acl. |
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*/ |
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public boolean removeEntry(Principal caller, AclEntry entry) |
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throws NotOwnerException; |
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/** |
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* Returns an enumeration for the set of allowed permissions for the |
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* specified principal (representing an entity such as an individual or |
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* a group). This set of allowed permissions is calculated as |
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* follows: |
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* |
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* <ul> |
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* |
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* <li>If there is no entry in this Access Control List for the |
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* specified principal, an empty permission set is returned. |
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* |
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* <li>Otherwise, the principal's group permission sets are determined. |
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* (A principal can belong to one or more groups, where a group is a |
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* group of principals, represented by the Group interface.) |
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* The group positive permission set is the union of all |
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* the positive permissions of each group that the principal belongs to. |
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* The group negative permission set is the union of all |
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* the negative permissions of each group that the principal belongs to. |
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* If there is a specific permission that occurs in both |
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* the positive permission set and the negative permission set, |
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* it is removed from both.<p> |
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* |
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* The individual positive and negative permission sets are also |
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* determined. The positive permission set contains the permissions |
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* specified in the positive ACL entry (if any) for the principal. |
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* Similarly, the negative permission set contains the permissions |
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* specified in the negative ACL entry (if any) for the principal. |
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* The individual positive (or negative) permission set is considered |
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* to be null if there is not a positive (negative) ACL entry for the |
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* principal in this ACL.<p> |
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* |
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* The set of permissions granted to the principal is then calculated |
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* using the simple rule that individual permissions always override |
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* the group permissions. That is, the principal's individual negative |
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* permission set (specific denial of permissions) overrides the group |
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* positive permission set, and the principal's individual positive |
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* permission set overrides the group negative permission set. |
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* |
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* </ul> |
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* |
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* @param user the principal whose permission set is to be returned. |
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* |
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* @return the permission set specifying the permissions the principal |
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* is allowed. |
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*/ |
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public Enumeration<Permission> getPermissions(Principal user); |
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/** |
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* Returns an enumeration of the entries in this ACL. Each element in |
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* the enumeration is of type AclEntry. |
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* |
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* @return an enumeration of the entries in this ACL. |
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*/ |
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public Enumeration<AclEntry> entries(); |
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/** |
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* Checks whether or not the specified principal has the specified |
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* permission. If it does, true is returned, otherwise false is returned. |
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* |
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* More specifically, this method checks whether the passed permission |
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* is a member of the allowed permission set of the specified principal. |
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* The allowed permission set is determined by the same algorithm as is |
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* used by the {@code getPermissions} method. |
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* |
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* @param principal the principal, assumed to be a valid authenticated |
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* Principal. |
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* |
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* @param permission the permission to be checked for. |
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* |
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* @return true if the principal has the specified permission, false |
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* otherwise. |
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* |
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* @see #getPermissions |
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*/ |
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public boolean checkPermission(Principal principal, Permission permission); |
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/** |
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* Returns a string representation of the |
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* ACL contents. |
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* |
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* @return a string representation of the ACL contents. |
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*/ |
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public String toString(); |
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} |