我在学Kafka春靴。我想在我的consumer类中添加第二个consumer，它订阅了与第一个主题相同的主题，但具有不同的groupID。这些类不是很复杂，当我只有第一个消费Json的消费者（或者至少输出是Json？）时，它们就可以工作。还有一点需要说明的是，我从一个生产者和消费者开始，他们使用@EnableBindings方法，但这种方法不受欢迎，所以我正在学习正确/新的方法。

任何提示！请让我走上正确的道路。

我有很多Maven依赖项，所以我只是总结一下：它包括spring-kafka、kafka-stream、spring-boot-starter-jpa等等......

应用程序属性，我不确定底部的标头属性是否正确：

spring.kafka.bootstrap-servers=localhost:29092
spring.kafka.consumer.properties.spring.json.trusted.packages=*
spring.kafka.consumer.auto-offset-reset=earliest

spring.kafka.consumer.properties.key-deserializer=org.apache.kafka.common.serialization.ErrorHandlingDeserializer

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

spring.kafka.consumer.properties.spring.deserializer.key.delegate.class: org.apache.kafka.common.serialization.StringDeserializer
spring.kafka.consumer.properties.spring.deserializer.value.delegate.class: org.springframework.kafka.support.serializer.JsonDeserializer

spring.kafka.producer.properties.key-serializer=org.apache.kafka.common.serialization.StringSerializer
spring.kafka.producer.properties.value-serializer=org.springframework.kafka.support.serializer.JsonSerializer

spring.kafka.producer.properties.spring.json.add.type.headers=false
spring.kafka.consumer.properties.spring.json.use.type.headers=false

#cockroachDB configs omitted

消费者类别：

@Service
public class BookConsumer {
    
    @Autowired
    public BookConsumer(BookService bookService) {
        this.bookService=bookService;
    }
    
    private final BookService bookService;
    
    @KafkaListener(topics="testKafka", groupId="group2")
    public void consume(BookDto books) {
        System.out.println("saved!");
        bookService.save(books);
    }
    
    @KafkaListener(topics="testKafka", groupId="group_id")
    public void consumeMessage(BookDto message){
        System.out.println(message);
    }
}

制作人阶层：

@Service
public class BookProducer {
    
    @Autowired
    private KafkaTemplate<String,BookDto> jsonTemplate;
    
    
    public void sendBookEvent(BookDto book) {
        this.jsonTemplate.send("testKafka", book);
    }
    
    public void sendJson(BookDto booklist) {
        this.jsonTemplate.send("testKafka", booklist);
    }
    
}

我还有一个调用事物的Rest控制器，我将只包括与生产者和消费者相关的两个。它是“/sendBookFromList”，应该用于当前无论如何都不工作的消费者：

@RestController
public class HelloController {
    
    private final BookProducer producer;
    
    @Autowired
    private final BookService bookService;
    
    @Autowired
    public HelloController(BookProducer producer, BookService bookService) {
        this.producer=producer;
        this.bookService=bookService;
    }
    

    public List<BookDto> makeList() {
        List<BookDto> readingList = new ArrayList<BookDto>();
        readingList.add(new BookDto(1, "Needful Things", "Stephen King"));
        readingList.add(new BookDto(2, "The Three-Body Problem", "Liu Cixin"));
        readingList.add(new BookDto(666, "Cujo", "Stephen King"));
        readingList.add(new BookDto(8, "The Castle", "Franz Kafka"));
        return readingList;
    }

    @RequestMapping("json/{pos}")
    public String sendJson(@PathVariable("pos") Integer pos) {
        producer.sendJson(makeList().get(pos));
        return "BookDto sent!";
    }

    @RequestMapping("/sendBookFromList/{listPos}")
    public String sendBooks(@PathVariable("listPos") Integer pos) {
        producer.sendBookEvent(makeList().get(pos));
        return "added!";
    }

我有一个BookDto类和一个实体，因为我将它连接到一个蟑螂数据库，我将包括它以防万一：

public class BookDto {

    private Integer id;
    private String name;
    private String Author;
    
    public BookDto() {
        
    }

    public BookDto(Integer id, String name, String Author) {
        this.id = id;
        this.name = name;
        this.Author = Author;
    }

//I'll omit the getter and setters here but they exist!
    
      @Override public String toString() {
          return "Book "+id+": "+name+" by "+Author; }   
}

//I'm using Lombok as well, I didn't forget my constructors and stuff I swear!
@Entity(name="BOOK")
@Data
public class Book {
    
    @Id 
    private Integer id;
    
    private String name;
    private String author;

}

为了澄清，我使用了映射器，因为我认为这可能是从Dto到实体的转换之间的问题。我认为它不起作用，因为这是错误消息（过去是Book而不是BookDto，没有映射器）：

Listener method could not be invoked with the incoming message
Endpoint handler details:
Method [public void com.Book.kafka.BookConsumer.consume(com.Book.kafka.BookDto)]

Cannot convert from [[B] to [com.Book.kafka.BookDto] for GenericMessage [payload=byte[48], headers={kafka_offset=151, kafka_consumer=org.apache.kafka.clients.consumer.KafkaConsumer@1ce9bcc9, kafka_timestampType=CREATE_TIME, kafka_receivedPartitionId=0, kafka_receivedTopic=testKafka, kafka_receivedTimestamp=1649930203804, __TypeId__=[B@163eece4, kafka_groupId=group2}]

附加信息：我正在docker中运行Kafka和ZooGuard