/* * Copyright 2017-2020 original authors * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * https://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package io.micronaut.configuration.kafka.bind; import io.micronaut.core.annotation.AnnotationMetadata; import io.micronaut.core.convert.ArgumentConversionContext; import io.micronaut.core.convert.ConversionService; import io.micronaut.messaging.annotation.Header; import org.apache.kafka.clients.consumer.ConsumerRecord; import org.apache.kafka.common.header.Headers; import javax.inject.Singleton; import java.util.Optional; /** * Binds Kafka headers to arguments. * * @param <T> The target type * @author Graeme Rocher * @since 1.0 */ @Singleton public class KafkaHeaderBinder<T> implements AnnotatedConsumerRecordBinder<Header, T> { @Override public Class<Header> annotationType() { return Header.class; } @Override public BindingResult<T> bind(ArgumentConversionContext<T> context, ConsumerRecord<?, ?> source) { Headers headers = source.headers(); AnnotationMetadata annotationMetadata = context.getAnnotationMetadata(); String name = annotationMetadata.getValue(Header.class, "name", String.class) .orElseGet(() -> annotationMetadata.getValue(Header.class, String.class) .orElse(context.getArgument().getName())); Iterable<org.apache.kafka.common.header.Header> value = headers.headers(name); if (value.iterator().hasNext()) { Optional<T> converted = ConversionService.SHARED.convert(value, context); return () -> converted; } else if (context.getArgument().getType() == Optional.class) { //noinspection unchecked return () -> (Optional<T>) Optional.of(Optional.empty()); } else { //noinspection unchecked return BindingResult.EMPTY; } } }