Apache Kafka-Spring Kafka将泛型反序列化为对象而非LinkedHashMap

本是古典何须时尚 2022-11-15 11:28 77阅读 0赞

### 文章目录 ###

*  Pre
 *  Question
 *  Answer
 *  扩展知识

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9hcnRpc2FuLmJsb2cuY3Nkbi5uZXQ_size_16_color_FFFFFF_t_70]

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# Pre #

#kafka
    spring.kafka.bootstrap-servers=10.11.114.247:9092
    spring.kafka.producer.acks=1
    spring.kafka.producer.retries=3
    spring.kafka.producer.batch-size=16384
    spring.kafka.producer.buffer-memory=33554432
    spring.kafka.producer.key-serializer=org.apache.kafka.common.serialization.StringSerializer
    spring.kafka.producer.value-serializer=org.springframework.kafka.support.serializer.JsonSerializer
    
    
    spring.kafka.consumer.group-id=zfprocessor_group
    spring.kafka.consumer.enable-auto-commit=false
    spring.kafka.consumer.auto-offset-reset=earliest
    spring.kafka.consumer.key-deserializer=org.apache.kafka.common.serialization.StringDeserializer
    spring.kafka.consumer.value-deserializer=org.springframework.kafka.support.serializer.JsonDeserializer
    spring.kafka.consumer.properties.spring.json.trusted.packages=com.artisan.common.entity.messages
    spring.kafka.consumer.max-poll-records=500
    spring.kafka.consumer.fetch-min-size=10
    spring.kafka.consumer.fetch-max-wait=10000ms
    
    spring.kafka.listener.missing-topics-fatal=false
    spring.kafka.listener.type=batch
    spring.kafka.listener.ack-mode=manual
    
    
    logging.level.org.springframework.kafka=ERROR
    logging.level.org.apache.kafka=ERROR

我们看看消费者反序列化，解析value的配置

spring.kafka.consumer.value-deserializer=org.springframework.kafka.support.serializer.JsonDeserializer

# Question #

spring kafka 使用Jackson序列化， 如果存入kafka中的对象 包含 泛型，那么 默认情况下，这个泛型对象会被Jackson反序列为 LinkedHashMap . 抛出类型转换异常…

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# Answer #

在实体类上增加如下注解

@Data
    public class Message<T> { 
       
        private int messageCode;
    
        
        @JsonTypeInfo(use = JsonTypeInfo.Id.CLASS,include = JsonTypeInfo.As.PROPERTY,property = "@class")
        private T messageContent;
    
    }

反序列化后，多了个节点

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70]

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![在这里插入图片描述][20210331190215719.gif_pic_center]

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# 扩展知识 #

[Jackson JSON - Using @JsonTypeInfo annotation to handle polymorphic types][Jackson JSON - Using _JsonTypeInfo annotation to handle polymorphic types]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9hcnRpc2FuLmJsb2cuY3Nkbi5uZXQ_size_16_color_FFFFFF_t_70]: /images/20221022/2efea685ca2348cdaa11e2bb54442374.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70]: /images/20221022/1c11811b0d374d6f9feaa6bb9739fe6c.png
[20210331190215719.gif_pic_center]: https://img-blog.csdnimg.cn/20210331190215719.gif#pic_center
[Jackson JSON - Using _JsonTypeInfo annotation to handle polymorphic types]: https://www.logicbig.com/tutorials/misc/jackson/jackson-json-type-info-annotation.html