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     */
019    package org.apache.shiro.realm;
020    
021    import org.apache.shiro.authc.AuthenticationException;
022    import org.apache.shiro.authc.AuthenticationInfo;
023    import org.apache.shiro.authc.AuthenticationToken;
024    
025    /**
026     * A <tt>Realm</tt> is a security component that can access application-specific security entities
027     * such as users, roles, and permissions to determine authentication and authorization operations.
028     *
029     * <p><tt>Realm</tt>s usually have a 1-to-1 correspondance with a datasource such as a relational database,
030     * file sysetem, or other similar resource.  As such, implementations of this interface use datasource-specific APIs to
031     * determine authorization data (roles, permissions, etc), such as JDBC, File IO, Hibernate or JPA, or any other
032     * Data Access API.  They are essentially security-specific
033     * <a href="http://en.wikipedia.org/wiki/Data_Access_Object" target="_blank">DAO</a>s.
034     *
035     * <p>Because most of these datasources usually contain Subject (a.k.a. User) information such as usernames and
036     * passwords, a Realm can act as a pluggable authentication module in a
037     * <a href="http://en.wikipedia.org/wiki/Pluggable_Authentication_Modules">PAM</a> configuration.  This allows a Realm to
038     * perform <i>both</i> authentication and authorization duties for a single datasource, which caters to the large
039     * majority of applications.  If for some reason you don't want your Realm implementation to perform authentication
040     * duties, you should override the {@link #supports(org.apache.shiro.authc.AuthenticationToken)} method to always
041     * return <tt>false</tt>.
042     *
043     * <p>Because every application is different, security data such as users and roles can be
044     * represented in any number of ways.  Shiro tries to maintain a non-intrusive development philosophy whenever
045     * possible - it does not require you to implement or extend any <tt>User</tt>, <tt>Group</tt> or <tt>Role</tt>
046     * interfaces or classes.
047     *
048     * <p>Instead, Shiro allows applications to implement this interface to access environment-specific datasources
049     * and data model objects.  The implementation can then be plugged in to the application's Shiro configuration.
050     * This modular technique abstracts away any environment/modeling details and allows Shiro to be deployed in
051     * practically any application environment.
052     *
053     * <p>Most users will not implement the <tt>Realm</tt> interface directly, but will extend one of the subclasses,
054     * {@link org.apache.shiro.realm.AuthenticatingRealm AuthenticatingRealm} or {@link org.apache.shiro.realm.AuthorizingRealm}, greatly reducing the effort requird
055     * to implement a <tt>Realm</tt> from scratch.</p>
056     *
057     * @see org.apache.shiro.realm.CachingRealm CachingRealm
058     * @see org.apache.shiro.realm.AuthenticatingRealm AuthenticatingRealm
059     * @see org.apache.shiro.realm.AuthorizingRealm AuthorizingRealm
060     * @see org.apache.shiro.authc.pam.ModularRealmAuthenticator ModularRealmAuthenticator
061     * @since 0.1
062     */
063    public interface Realm {
064    
065        /**
066         * Returns the (application-unique) name assigned to this <code>Realm</code>. All realms configured for a single
067         * application must have a unique name.
068         *
069         * @return the (application-unique) name assigned to this <code>Realm</code>.
070         */
071        String getName();
072    
073        /**
074         * Returns <tt>true</tt> if this realm wishes to authenticate the Subject represented by the given
075         * {@link org.apache.shiro.authc.AuthenticationToken AuthenticationToken} instance, <tt>false</tt> otherwise.
076         *
077         * <p>If this method returns <tt>false</tt>, it will not be called to authenticate the Subject represented by
078         * the token - more specifically, a <tt>false</tt> return value means this Realm instance's
079         * {@link #getAuthenticationInfo} method will not be invoked for that token.
080         *
081         * @param token the AuthenticationToken submitted for the authentication attempt
082         * @return <tt>true</tt> if this realm can/will authenticate Subjects represented by specified token,
083         *         <tt>false</tt> otherwise.
084         */
085        boolean supports(AuthenticationToken token);
086    
087        /**
088         * Returns an account's authentication-specific information for the specified <tt>token</tt>,
089         * or <tt>null</tt> if no account could be found based on the <tt>token</tt>.
090         *
091         * <p>This method effectively represents a login attempt for the corresponding user with the underlying EIS datasource.
092         * Most implementations merely just need to lookup and return the account data only (as the method name implies)
093         * and let Shiro do the rest, but implementations may of course perform eis specific login operations if so
094         * desired.
095         *
096         * @param token the application-specific representation of an account principal and credentials.
097         * @return the authentication information for the account associated with the specified <tt>token</tt>,
098         *         or <tt>null</tt> if no account could be found.
099         * @throws org.apache.shiro.authc.AuthenticationException
100         *          if there is an error obtaining or constructing an AuthenticationInfo object based on the
101         *          specified <tt>token</tt> or implementation-specifc login behavior fails.
102         */
103        AuthenticationInfo getAuthenticationInfo(AuthenticationToken token) throws AuthenticationException;
104    
105    }