1/*
2 * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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24 */
25
26package java.security.acl;
27
28import java.util.Enumeration;
29import java.security.Principal;
30
31/**
32 * This is the interface used for representing one entry in an Access
33 * Control List (ACL).<p>
34 *
35 * An ACL can be thought of as a data structure with multiple ACL entry
36 * objects. Each ACL entry object contains a set of permissions associated
37 * with a particular principal. (A principal represents an entity such as
38 * an individual user or a group). Additionally, each ACL entry is specified
39 * as being either positive or negative. If positive, the permissions are
40 * to be granted to the associated principal. If negative, the permissions
41 * are to be denied. Each principal can have at most one positive ACL entry
42 * and one negative entry; that is, multiple positive or negative ACL
43 * entries are not allowed for any principal.
44 *
45 * Note: ACL entries are by default positive. An entry becomes a
46 * negative entry only if the
47 * {@link #setNegativePermissions() setNegativePermissions}
48 * method is called on it.
49 *
50 * @see java.security.acl.Acl
51 *
52 * @author      Satish Dharmaraj
53 */
54public interface AclEntry extends Cloneable {
55
56    /**
57     * Specifies the principal for which permissions are granted or denied
58     * by this ACL entry. If a principal was already set for this ACL entry,
59     * false is returned, otherwise true is returned.
60     *
61     * @param user the principal to be set for this entry.
62     *
63     * @return true if the principal is set, false if there was
64     * already a principal set for this entry.
65     *
66     * @see #getPrincipal
67     */
68    public boolean setPrincipal(Principal user);
69
70    /**
71     * Returns the principal for which permissions are granted or denied by
72     * this ACL entry. Returns null if there is no principal set for this
73     * entry yet.
74     *
75     * @return the principal associated with this entry.
76     *
77     * @see #setPrincipal
78     */
79    public Principal getPrincipal();
80
81    /**
82     * Sets this ACL entry to be a negative one. That is, the associated
83     * principal (e.g., a user or a group) will be denied the permission set
84     * specified in the entry.
85     *
86     * Note: ACL entries are by default positive. An entry becomes a
87     * negative entry only if this {@code setNegativePermissions}
88     * method is called on it.
89     */
90    public void setNegativePermissions();
91
92    /**
93     * Returns true if this is a negative ACL entry (one denying the
94     * associated principal the set of permissions in the entry), false
95     * otherwise.
96     *
97     * @return true if this is a negative ACL entry, false if it's not.
98     */
99    public boolean isNegative();
100
101    /**
102     * Adds the specified permission to this ACL entry. Note: An entry can
103     * have multiple permissions.
104     *
105     * @param permission the permission to be associated with
106     * the principal in this entry.
107     *
108     * @return true if the permission was added, false if the
109     * permission was already part of this entry's permission set.
110     */
111    public boolean addPermission(Permission permission);
112
113    /**
114     * Removes the specified permission from this ACL entry.
115     *
116     * @param permission the permission to be removed from this entry.
117     *
118     * @return true if the permission is removed, false if the
119     * permission was not part of this entry's permission set.
120     */
121    public boolean removePermission(Permission permission);
122
123    /**
124     * Checks if the specified permission is part of the
125     * permission set in this entry.
126     *
127     * @param permission the permission to be checked for.
128     *
129     * @return true if the permission is part of the
130     * permission set in this entry, false otherwise.
131     */
132    public boolean checkPermission(Permission permission);
133
134    /**
135     * Returns an enumeration of the permissions in this ACL entry.
136     *
137     * @return an enumeration of the permissions in this ACL entry.
138     */
139    public Enumeration<Permission> permissions();
140
141    /**
142     * Returns a string representation of the contents of this ACL entry.
143     *
144     * @return a string representation of the contents.
145     */
146    public String toString();
147
148    /**
149     * Clones this ACL entry.
150     *
151     * @return a clone of this ACL entry.
152     */
153    public Object clone();
154}
155