src/org/jsecurity/web/tags/GuestTag.java

/*
 * Copyright 2005-2008 Les Hazlewood
 *
 * Licensed 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.jsecurity.web.tags;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;

/**
 * JSP tag that renders the tag body if the current user <em>is not</em> known to the system, either because they
 * haven't logged in yet, or because they have no 'RememberMe' identity.
 *
 * <p>The logically opposite tag of this one is the {@link UserTag}.  Please read that class's JavaDoc as it explains
 * more about the differences between Authenticated/Unauthenticated and User/Guest semantic differences.
 *
 * @author Les Hazlewood
 * @since 0.9
 */
public class GuestTag extends SecureTag {

    public int onDoStartTag() throws JspException {
        if ( getSubject() == null || getSubject().getPrincipal() == null ) {
            if ( log.isTraceEnabled() ) {
                log.trace( "Subject does not exist or does not have a known identity (aka 'principal').  " +
                    "Tag body will be evaluated." );
            }
            return TagSupport.EVAL_BODY_INCLUDE;
        } else {
            if ( log.isTraceEnabled() ) {
                log.trace( "Subject exists or has a known identity (aka 'principal').  " +
                    "Tag body will not be evaluated." );
            }
            return TagSupport.SKIP_BODY;
        }
    }

}