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.web.tags;
020    
021    import javax.servlet.jsp.JspException;
022    import javax.servlet.jsp.tagext.TagSupport;
023    
024    import org.slf4j.Logger;
025    import org.slf4j.LoggerFactory;
026    
027    
028    /**
029     * JSP tag that renders the tag body if the current user <em>is not</em> known to the system, either because they
030     * haven't logged in yet, or because they have no 'RememberMe' identity.
031     *
032     * <p>The logically opposite tag of this one is the {@link UserTag}.  Please read that class's JavaDoc as it explains
033     * more about the differences between Authenticated/Unauthenticated and User/Guest semantic differences.
034     *
035     * @since 0.9
036     */
037    public class GuestTag extends SecureTag {
038    
039        //TODO - complete JavaDoc
040    
041        private static final Logger log = LoggerFactory.getLogger(GuestTag.class);
042    
043        public int onDoStartTag() throws JspException {
044            if (getSubject() == null || getSubject().getPrincipal() == null) {
045                if (log.isTraceEnabled()) {
046                    log.trace("Subject does not exist or does not have a known identity (aka 'principal').  " +
047                            "Tag body will be evaluated.");
048                }
049                return TagSupport.EVAL_BODY_INCLUDE;
050            } else {
051                if (log.isTraceEnabled()) {
052                    log.trace("Subject exists or has a known identity (aka 'principal').  " +
053                            "Tag body will not be evaluated.");
054                }
055                return TagSupport.SKIP_BODY;
056            }
057        }
058    
059    }