/*

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF licenses this file

  * to you under the Apache License, Version 2.0 (the

  * "License"); you may not use this file except in compliance

  * with the License.  You may obtain a copy of the License at

  *

  *     http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing,

  * software distributed under the License is distributed on an

  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

  * KIND, either express or implied.  See the License for the

  * specific language governing permissions and limitations

  * under the License.

  */

 package org.apache.shiro.realm;

 import org.apache.shiro.authc.AuthenticationException;

 import org.apache.shiro.authc.AuthenticationInfo;

 import org.apache.shiro.authc.AuthenticationToken;

 /**

  * A <tt>Realm</tt> is a security component that can access application-specific security entities

  * such as users, roles, and permissions to determine authentication and authorization operations.

  *

  * <p><tt>Realm</tt>s usually have a 1-to-1 correspondance with a datasource such as a relational database,

  * file sysetem, or other similar resource.  As such, implementations of this interface use datasource-specific APIs to

  * determine authorization data (roles, permissions, etc), such as JDBC, File IO, Hibernate or JPA, or any other

  * Data Access API.  They are essentially security-specific

  * <a href="http://en.wikipedia.org/wiki/Data_Access_Object" target="_blank">DAO</a>s.

  *

  * <p>Because most of these datasources usually contain Subject (a.k.a. User) information such as usernames and

  * passwords, a Realm can act as a pluggable authentication module in a

  * <a href="http://en.wikipedia.org/wiki/Pluggable_Authentication_Modules">PAM</a> configuration.  This allows a Realm to

  * perform <i>both</i> authentication and authorization duties for a single datasource, which caters to the large

  * majority of applications.  If for some reason you don't want your Realm implementation to perform authentication

  * duties, you should override the {@link #supports(org.apache.shiro.authc.AuthenticationToken)} method to always

  * return <tt>false</tt>.

  *

  * <p>Because every application is different, security data such as users and roles can be

  * represented in any number of ways.  Shiro tries to maintain a non-intrusive development philosophy whenever

  * possible - it does not require you to implement or extend any <tt>User</tt>, <tt>Group</tt> or <tt>Role</tt>

  * interfaces or classes.

  *

  * <p>Instead, Shiro allows applications to implement this interface to access environment-specific datasources

  * and data model objects.  The implementation can then be plugged in to the application's Shiro configuration.

  * This modular technique abstracts away any environment/modeling details and allows Shiro to be deployed in

  * practically any application environment.

  *

  * <p>Most users will not implement the <tt>Realm</tt> interface directly, but will extend one of the subclasses,

  * {@link org.apache.shiro.realm.AuthenticatingRealm AuthenticatingRealm} or {@link org.apache.shiro.realm.AuthorizingRealm}, greatly reducing the effort requird

  * to implement a <tt>Realm</tt> from scratch.</p>

  *

  * @see org.apache.shiro.realm.CachingRealm CachingRealm

  * @see org.apache.shiro.realm.AuthenticatingRealm AuthenticatingRealm

  * @see org.apache.shiro.realm.AuthorizingRealm AuthorizingRealm

  * @see org.apache.shiro.authc.pam.ModularRealmAuthenticator ModularRealmAuthenticator

  * @since 0.1

  */

 public interface Realm {

     /**

      * Returns the (application-unique) name assigned to this <code>Realm</code>. All realms configured for a single

      * application must have a unique name.

      *

      * @return the (application-unique) name assigned to this <code>Realm</code>.

      */

     String getName();

     /**

      * Returns <tt>true</tt> if this realm wishes to authenticate the Subject represented by the given

      * {@link org.apache.shiro.authc.AuthenticationToken AuthenticationToken} instance, <tt>false</tt> otherwise.

      *

      * <p>If this method returns <tt>false</tt>, it will not be called to authenticate the Subject represented by

      * the token - more specifically, a <tt>false</tt> return value means this Realm instance's

      * {@link #getAuthenticationInfo} method will not be invoked for that token.

      *

      * @param token the AuthenticationToken submitted for the authentication attempt

      * @return <tt>true</tt> if this realm can/will authenticate Subjects represented by specified token,

      *         <tt>false</tt> otherwise.

      */

     boolean supports(AuthenticationToken token);

     /**

      * Returns an account's authentication-specific information for the specified <tt>token</tt>,

      * or <tt>null</tt> if no account could be found based on the <tt>token</tt>.

      *

      * <p>This method effectively represents a login attempt for the corresponding user with the underlying EIS datasource.

      * Most implementations merely just need to lookup and return the account data only (as the method name implies)

      * and let Shiro do the rest, but implementations may of course perform eis specific login operations if so

      * desired.

      *

      * @param token the application-specific representation of an account principal and credentials.

      * @return the authentication information for the account associated with the specified <tt>token</tt>,

      *         or <tt>null</tt> if no account could be found.

      * @throws org.apache.shiro.authc.AuthenticationException

      *          if there is an error obtaining or constructing an AuthenticationInfo object based on the

      *          specified <tt>token</tt> or implementation-specifc login behavior fails.

      */

     AuthenticationInfo getAuthenticationInfo(AuthenticationToken token) throws AuthenticationException;

 }