001/**
002 * Copyright (C) 2006-2020 Talend Inc. - www.talend.com
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016package org.talend.sdk.component.api.service.interceptor;
017
018import java.lang.annotation.Annotation;
019import java.lang.reflect.Method;
020import java.util.Optional;
021import java.util.stream.Stream;
022
023/**
024 * The hook used to implement an interceptor.
025 * It can be associated to a {@link Intercepts}
026 * marker.
027 *
028 * IMPORTANT: if you want a delegate instance you have to provide a constructor
029 * taking an object as parameter. Alternatively you can use a {@literal BiFunction<Method, Object[], Object>}
030 * constructor parameter to be able to delegate the invocation. Else you must provide a default constructor.
031 *
032 * NOTE: if your interceptor doesn't take an invoker as parameter
033 * ({@literal java.util.function.BiFunction<Method, Object[], Object>})
034 * then the interceptor chain can be broken if you invoke yourself a method. It is recommended to respect it.
035 */
036public interface InterceptorHandler {
037
038    /**
039     * Called instead of the delegate method.
040     *
041     * @param method th emethod being invoked.
042     * @param args the parameters of the method.
043     * @return the returned value of the method.
044     */
045    Object invoke(Method method, Object[] args);
046
047    default <T extends Annotation> Optional<T> findAnnotation(final Method method, final Class<T> type) {
048        return Optional
049                .ofNullable((T) Stream
050                        .of(method.getAnnotations())
051                        .filter(a -> a.annotationType() == type)
052                        .findFirst()
053                        .orElseGet(() -> Stream
054                                .of(method.getDeclaringClass().getAnnotations())
055                                .filter(a -> a.annotationType() == type)
056                                .findFirst()
057                                .orElse(null)));
058    }
059}