Java tutorial
/* * 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 correspondence with a datasource such as a relational database, * file system, 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-specific login behavior fails. */ AuthenticationInfo getAuthenticationInfo(AuthenticationToken token) throws AuthenticationException; }