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.authz; /** * A Permission represents the ability to perform an action or access a resource. A Permission is the most * granular, or atomic, unit in a system's security policy and is the cornerstone upon which fine-grained security * models are built. * <p/> * It is important to understand a Permission instance only represents functionality or access - it does not grant it. * Granting access to an application functionality or a particular resource is done by the application's security * configuration, typically by assigning Permissions to users, roles and/or groups. * <p/> * Most typical systems are what the Shiro team calls <em>role-based</em> in nature, where a role represents * common behavior for certain user types. For example, a system might have an <em>Administrator</em> role, a * <em>User</em> or <em>Guest</em> roles, etc. * <p/> * But if you have a dynamic security model, where roles can be created and deleted at runtime, you can't hard-code * role names in your code. In this environment, roles themselves aren't very useful. What matters is what * <em>permissions</em> are assigned to these roles. * <p/> * Under this paradigm, permissions are immutable and reflect an application's raw functionality * (opening files, accessing a web URL, creating users, etc). This is what allows a system's security policy * to be dynamic: because Permissions represent raw functionality and only change when the application's * source code changes, they are immutable at runtime - they represent 'what' the system can do. Roles, users, and * groups are the 'who' of the application. Determining 'who' can do 'what' then becomes a simple exercise of * associating Permissions to roles, users, and groups in some way. * <p/> * Most applications do this by associating a named role with permissions (i.e. a role 'has a' collection of * Permissions) and then associate users with roles (i.e. a user 'has a' collection of roles) so that by transitive * association, the user 'has' the permissions in their roles. There are numerous variations on this theme * (permissions assigned directly to users, or assigned to groups, and users added to groups and these groups in turn * have roles, etc, etc). When employing a permission-based security model instead of a role-based one, users, roles, * and groups can all be created, configured and/or deleted at runtime. This enables an extremely powerful security * model. * <p/> * A benefit to Shiro is that, although it assumes most systems are based on these types of static role or * dynamic role w/ permission schemes, it does not require a system to model their security data this way - all * Permission checks are relegated to {@link org.apache.shiro.realm.Realm} implementations, and only those * implementations really determine how a user 'has' a permission or not. The Realm could use the semantics described * here, or it could utilize some other mechanism entirely - it is always up to the application developer. * <p/> * Shiro provides a very powerful default implementation of this interface in the form of the * {@link org.apache.shiro.authz.permission.WildcardPermission WildcardPermission}. We highly recommend that you * investigate this class before trying to implement your own <code>Permission</code>s. * * @see org.apache.shiro.authz.permission.WildcardPermission WildcardPermission * @since 0.2 */ public interface Permission { /** * Returns {@code true} if this current instance <em>implies</em> all the functionality and/or resource access * described by the specified {@code Permission} argument, {@code false} otherwise. * <p/> * <p>That is, this current instance must be exactly equal to or a <em>superset</em> of the functionality * and/or resource access described by the given {@code Permission} argument. Yet another way of saying this * would be: * <p/> * <p>If "permission1 implies permission2", i.e. <code>permission1.implies(permission2)</code> , * then any Subject granted {@code permission1} would have ability greater than or equal to that defined by * {@code permission2}. * * @param p the permission to check for behavior/functionality comparison. * @return {@code true} if this current instance <em>implies</em> all the functionality and/or resource access * described by the specified {@code Permission} argument, {@code false} otherwise. */ boolean implies(Permission p); }