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.authz.aop;
020    
021    import java.lang.annotation.Annotation;
022    
023    import org.apache.shiro.authz.AuthorizationException;
024    import org.apache.shiro.authz.UnauthenticatedException;
025    import org.apache.shiro.authz.annotation.RequiresGuest;
026    
027    
028    /**
029     * Checks to see if a @{@link org.apache.shiro.authz.annotation.RequiresGuest RequiresGuest} annotation
030     * is declared, and if so, ensures the calling <code>Subject</code> does <em>not</em>
031     * have an {@link org.apache.shiro.subject.Subject#getPrincipal() identity} before invoking the method.
032     * <p>
033     * This annotation essentially ensures that <code>subject.{@link org.apache.shiro.subject.Subject#getPrincipal() getPrincipal()} == null</code>.
034     *
035     * @since 0.9.0
036     */
037    public class GuestAnnotationHandler extends AuthorizingAnnotationHandler {
038    
039        /**
040         * Default no-argument constructor that ensures this interceptor looks for
041         *
042         * {@link org.apache.shiro.authz.annotation.RequiresGuest RequiresGuest} annotations in a method
043         * declaration.
044         */
045        public GuestAnnotationHandler() {
046            super(RequiresGuest.class);
047        }
048    
049        /**
050         * Ensures that the calling <code>Subject</code> is NOT a <em>user</em>, that is, they do not
051         * have an {@link org.apache.shiro.subject.Subject#getPrincipal() identity} before continuing.  If they are
052         * a user ({@link org.apache.shiro.subject.Subject#getPrincipal() Subject.getPrincipal()} != null), an
053         * <code>AuthorizingException</code> will be thrown indicating that execution is not allowed to continue.
054         *
055         * @param a the annotation to check for one or more roles
056         * @throws org.apache.shiro.authz.AuthorizationException
057         *          if the calling <code>Subject</code> is not a &quot;guest&quot;.
058         */
059        public void assertAuthorized(Annotation a) throws AuthorizationException {
060            if (a instanceof RequiresGuest && getSubject().getPrincipal() != null) {
061                throw new UnauthenticatedException("Attempting to perform a guest-only operation.  The current Subject is " +
062                        "not a guest (they have been authenticated or remembered from a previous login).  Access " +
063                        "denied.");
064            }
065        }
066    }