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 */
017package org.apache.logging.log4j.core.config.plugins.validation;
018
019import java.lang.annotation.Annotation;
020import java.lang.reflect.ParameterizedType;
021import java.lang.reflect.Type;
022import java.util.ArrayList;
023import java.util.Collection;
024
025import 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 */
032public 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<>();
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}