org.springframework.kafka.annotation.KafkaHandler Maven / Gradle / Ivy
/*
* 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;
}