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.authc.pam;
020    
021    import org.apache.shiro.authc.AuthenticationException;
022    import org.apache.shiro.authc.AuthenticationInfo;
023    import org.apache.shiro.authc.AuthenticationToken;
024    import org.apache.shiro.realm.Realm;
025    import org.apache.shiro.util.CollectionUtils;
026    
027    import java.util.Collection;
028    
029    /**
030     * {@link AuthenticationStrategy} implementation that only accepts the account data from
031     * the first successfully consulted Realm and ignores all subsequent realms.  This is slightly
032     * different behavior than {@link AtLeastOneSuccessfulStrategy}, so please review both to see
033     * which one meets your needs better.
034     *
035     * @see AtLeastOneSuccessfulStrategy AtLeastOneSuccessfulAuthenticationStrategy
036     * @since 0.9
037     */
038    public class FirstSuccessfulStrategy extends AbstractAuthenticationStrategy {
039    
040        /**
041         * Returns {@code null} immediately, relying on this class's {@link #merge merge} implementation to return
042         * only the first {@code info} object it encounters, ignoring all subsequent ones.
043         */
044        public AuthenticationInfo beforeAllAttempts(Collection<? extends Realm> realms, AuthenticationToken token) throws AuthenticationException {
045            return null;
046        }
047    
048        /**
049         * Returns the specified {@code aggregate} instance if is non null and valid (that is, has principals and they are
050         * not empty) immediately, or, if it is null or not valid, the {@code info} argument is returned instead.
051         * <p/>
052         * This logic ensures that the first valid info encountered is the one retained and all subsequent ones are ignored,
053         * since this strategy mandates that only the info from the first successfully authenticated realm be used.
054         */
055        protected AuthenticationInfo merge(AuthenticationInfo info, AuthenticationInfo aggregate) {
056            if (aggregate != null && !CollectionUtils.isEmpty(aggregate.getPrincipals())) {
057                return aggregate;
058            }
059            return info != null ? info : aggregate;
060        }
061    }