001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.shiro.subject;
020
021import java.io.Serializable;
022import java.util.Collection;
023import java.util.List;
024import java.util.Set;
025
026/**
027 * A collection of all principals associated with a corresponding {@link Subject Subject}.  A <em>principal</em> is
028 * just a security term for an identifying attribute, such as a username or user id or social security number or
029 * anything else that can be considered an 'identifying' attribute for a {@code Subject}.
030 * <p/>
031 * A PrincipalCollection organizes its internal principals based on the {@code Realm} where they came from when the
032 * Subject was first created.  To obtain the principal(s) for a specific Realm, see the {@link #fromRealm} method.  You
033 * can also see which realms contributed to this collection via the {@link #getRealmNames() getRealmNames()} method.
034 *
035 * @see #getPrimaryPrincipal()
036 * @see #fromRealm(String realmName)
037 * @see #getRealmNames()
038 * @since 0.9
039 */
040public interface PrincipalCollection extends Iterable, Serializable {
041
042    /**
043     * Returns the primary principal used application-wide to uniquely identify the owning account/Subject.
044     * <p/>
045     * The value is usually always a uniquely identifying attribute specific to the data source that retrieved the
046     * account data.  Some examples:
047     * <ul>
048     * <li>a {@link java.util.UUID UUID}</li>
049     * <li>a {@code long} value such as a surrogate primary key in a relational database</li>
050     * <li>an LDAP UUID or static DN</li>
051     * <li>a String username unique across all user accounts</li>
052     * </ul>
053     * <h3>Multi-Realm Applications</h3>
054     * In a single-{@code Realm} application, typically there is only ever one unique principal to retain and that
055     * is the value returned from this method.  However, in a multi-{@code Realm} application, where the
056     * {@code PrincipalCollection} might retain principals across more than one realm, the value returned from this
057     * method should be the single principal that uniquely identifies the subject for the entire application.
058     * <p/>
059     * That value is of course application specific, but most applications will typically choose one of the primary
060     * principals from one of the {@code Realm}s.
061     * <p/>
062     * Shiro's default implementations of this interface make this
063     * assumption by usually simply returning {@link #iterator()}.{@link java.util.Iterator#next() next()}, which just
064     * returns the first returned principal obtained from the first consulted/configured {@code Realm} during the
065     * authentication attempt.  This means in a multi-{@code Realm} application, {@code Realm} configuration order
066     * matters if you want to retain this default heuristic.
067     * <p/>
068     * If this heuristic is not sufficient, most Shiro end-users will need to implement a custom
069     * {@link org.apache.shiro.authc.pam.AuthenticationStrategy}.  An {@code AuthenticationStrategy} has exact control
070     * over the {@link PrincipalCollection} returned at the end of an authentication attempt via the
071     * <code>AuthenticationStrategy#{@link org.apache.shiro.authc.pam.AuthenticationStrategy#afterAllAttempts(org.apache.shiro.authc.AuthenticationToken, org.apache.shiro.authc.AuthenticationInfo) afterAllAttempts}</code>
072     * implementation.
073     *
074     * @return the primary principal used to uniquely identify the owning account/Subject
075     * @since 1.0
076     */
077    Object getPrimaryPrincipal();
078
079    /**
080     * Returns the first discovered principal assignable from the specified type, or {@code null} if there are none
081     * of the specified type.
082     * <p/>
083     * Note that this will return {@code null} if the 'owning' subject has not yet logged in.
084     *
085     * @param type the type of the principal that should be returned.
086     * @return a principal of the specified type or {@code null} if there isn't one of the specified type.
087     */
088    <T> T oneByType(Class<T> type);
089
090    /**
091     * Returns all principals assignable from the specified type, or an empty Collection if no principals of that
092     * type are contained.
093     * <p/>
094     * Note that this will return an empty Collection if the 'owning' subject has not yet logged in.
095     *
096     * @param type the type of the principals that should be returned.
097     * @return a Collection of principals that are assignable from the specified type, or
098     *         an empty Collection if no principals of this type are associated.
099     */
100    <T> Collection<T> byType(Class<T> type);
101
102    /**
103     * Returns a single Subject's principals retrieved from all configured Realms as a List, or an empty List if
104     * there are not any principals.
105     * <p/>
106     * Note that this will return an empty List if the 'owning' subject has not yet logged in.
107     *
108     * @return a single Subject's principals retrieved from all configured Realms as a List.
109     */
110    List asList();
111
112    /**
113     * Returns a single Subject's principals retrieved from all configured Realms as a Set, or an empty Set if there
114     * are not any principals.
115     * <p/>
116     * Note that this will return an empty Set if the 'owning' subject has not yet logged in.
117     *
118     * @return a single Subject's principals retrieved from all configured Realms as a Set.
119     */
120    Set asSet();
121
122    /**
123     * Returns a single Subject's principals retrieved from the specified Realm <em>only</em> as a Collection, or an empty
124     * Collection if there are not any principals from that realm.
125     * <p/>
126     * Note that this will return an empty Collection if the 'owning' subject has not yet logged in.
127     *
128     * @param realmName the name of the Realm from which the principals were retrieved.
129     * @return the Subject's principals from the specified Realm only as a Collection or an empty Collection if there
130     *         are not any principals from that realm.
131     */
132    Collection fromRealm(String realmName);
133
134    /**
135     * Returns the realm names that this collection has principals for.
136     *
137     * @return the names of realms that this collection has one or more principals for.
138     */
139    Set<String> getRealmNames();
140
141    /**
142     * Returns {@code true} if this collection is empty, {@code false} otherwise.
143     *
144     * @return {@code true} if this collection is empty, {@code false} otherwise.
145     */
146    boolean isEmpty();
147}