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 }