    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;
    018
    019    import java.lang.annotation.Annotation;
    020    import java.lang.reflect.ParameterizedType;
    021    import java.lang.reflect.Type;
    022    import java.util.ArrayList;
    023    import java.util.Collection;
    024
    025    import org.apache.logging.log4j.core.util.ReflectionUtil;
    026
    027    /**
    028     * Utility class to locate an appropriate {@link ConstraintValidator} implementation for an annotation.
    029     *
    030     * @since 2.1
    031     */
    032    public final class ConstraintValidators {
    033
    034        private ConstraintValidators() {
    035        }
    036
    037        /**
    038         * Finds all relevant {@link ConstraintValidator} objects from an array of annotations. All validators will be
    039         * {@link ConstraintValidator#initialize(java.lang.annotation.Annotation) initialized} before being returned.
    040         *
    041         * @param annotations the annotations to find constraint validators for
    042         * @return a collection of ConstraintValidators for the given annotations
    043         */
    044        public static Collection<ConstraintValidator<?>> findValidators(final Annotation... annotations) {
    045            final Collection<ConstraintValidator<?>> validators =
    046                new ArrayList<ConstraintValidator<?>>();
    047            for (final Annotation annotation : annotations) {
    048                final Class<? extends Annotation> type = annotation.annotationType();
    049                if (type.isAnnotationPresent(Constraint.class)) {
    050                    final ConstraintValidator<?> validator = getValidator(annotation, type);
    051                    if (validator != null) {
    052                        validators.add(validator);
    053                    }
    054                }
    055            }
    056            return validators;
    057        }
    058
    059        private static <A extends Annotation> ConstraintValidator<A> getValidator(final A annotation,
    060                                                                                  final Class<? extends A> type) {
    061            final Constraint constraint = type.getAnnotation(Constraint.class);
    062            final Class<? extends ConstraintValidator<?>> validatorClass = constraint.value();
    063            if (type.equals(getConstraintValidatorAnnotationType(validatorClass))) {
    064                @SuppressWarnings("unchecked") // I don't think we could be any more thorough in validation here
    065                final ConstraintValidator<A> validator = (ConstraintValidator<A>)
    066                    ReflectionUtil.instantiate(validatorClass);
    067                validator.initialize(annotation);
    068                return validator;
    069            }
    070            return null;
    071        }
    072
    073        private static Type getConstraintValidatorAnnotationType(final Class<? extends ConstraintValidator<?>> type) {
    074            for (final Type parentType : type.getGenericInterfaces()) {
    075                if (parentType instanceof ParameterizedType) {
    076                    final ParameterizedType parameterizedType = (ParameterizedType) parentType;
    077                    if (ConstraintValidator.class.equals(parameterizedType.getRawType())) {
    078                        return parameterizedType.getActualTypeArguments()[0];
    079                    }
    080                }
    081            }
    082            return Void.TYPE;
    083        }
    084    }