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/*
 * Copyright 2015-2019 the original author or 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 org.springframework.kafka.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.springframework.messaging.handler.annotation.MessageMapping;

/**
 * Annotation that marks a method to be the target of a Kafka message
 * listener within a class that is annotated with {@link KafkaListener}.
 *
 * 

See the {@link KafkaListener} for information about permitted method signatures * and available parameters. *

It is important to understand that when a message arrives, the method selection * depends on the payload type. The type is matched with a single non-annotated parameter, * or one that is annotated with {@code @Payload}. * There must be no ambiguity - the system * must be able to select exactly one method based on the payload type. * * @author Gary Russell * * @see EnableKafka * @see KafkaListener * @see KafkaListenerAnnotationBeanPostProcessor */ @Target({ ElementType.METHOD, ElementType.ANNOTATION_TYPE }) @Retention(RetentionPolicy.RUNTIME) @MessageMapping @Documented public @interface KafkaHandler { /** * When true, designate that this is the default fallback method if the payload type * matches no other {@link KafkaHandler} method. Only one method can be so designated. * @return true if this is the default method. * @since 2.1.3 */ boolean isDefault() default false; }





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