001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements. See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache license, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License. You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the license for the specific language governing permissions and
015     * limitations under the license.
016     */
017    package org.apache.logging.log4j.core.config.plugins.validation.validators;
018    
019    import java.util.Collection;
020    import java.util.Map;
021    
022    import org.apache.logging.log4j.Logger;
023    import org.apache.logging.log4j.core.config.plugins.validation.ConstraintValidator;
024    import org.apache.logging.log4j.core.config.plugins.validation.constraints.Required;
025    import org.apache.logging.log4j.status.StatusLogger;
026    
027    /**
028     * Validator that checks an object for emptiness. Emptiness is defined here as:
029     * <ul>
030     * <li>The value {@code null}</li>
031     * <li>An object of type {@link CharSequence} with length 0</li>
032     * <li>An empty array</li>
033     * <li>An empty {@link Collection}</li>
034     * <li>An empty {@link Map}</li>
035     * </ul>
036     *
037     * @since 2.1
038     */
039    public class RequiredValidator implements ConstraintValidator<Required> {
040    
041        private static final Logger LOGGER = StatusLogger.getLogger();
042    
043        private Required annotation;
044    
045        @Override
046        public void initialize(final Required annotation) {
047            this.annotation = annotation;
048        }
049    
050        @Override
051        public boolean isValid(final Object value) {
052            if (value == null) {
053                return err();
054            }
055            if (value instanceof CharSequence) {
056                final CharSequence sequence = (CharSequence) value;
057                return sequence.length() != 0 || err();
058            }
059            final Class<?> clazz = value.getClass();
060            if (clazz.isArray()) {
061                final Object[] array = (Object[]) value;
062                return array.length != 0 || err();
063            }
064            if (Collection.class.isAssignableFrom(clazz)) {
065                final Collection<?> collection = (Collection<?>) value;
066                return collection.size() != 0 || err();
067            }
068            if (Map.class.isAssignableFrom(clazz)) {
069                final Map<?, ?> map = (Map<?, ?>) value;
070                return map.size() != 0 || err();
071            }
072            LOGGER.debug("Encountered type [{}] which can only be checked for null.", clazz.getName());
073            return true;
074        }
075    
076        private boolean err() {
077            LOGGER.error(annotation.message());
078            return false;
079        }
080    }