Spring Boot | How to consume JSON messages using Apache Kafka

// Java program to implement a
// student class

// Creating a student class
public class Student {

    // Data members of the class
    int id;
    String firstName;
    String lastName;

    // Constructor of the student
    // Class
    public Student()
    {
    }

    // Parameterized constructor of
    // the student class
    public Student(int id, String firstName,
                   String lastName)
    {
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
    }

    @Override
    public String toString()
    {
        return "Student{"
            + "id = " + id
            + ", firstName = '" + firstName + "'"
            + ", lastName = '" + lastName + "'"
            + "}";
    }
}

@EnableKafka
@Configuration
public class Config {

    // Function to establish a connection
    // between Spring application
    // and Kafka server
    @Bean
    public ConsumerFactory<String, Student>
    studentConsumer()
    {

        // HashMap to store the configurations
        Map<String, Object> map
            = new HashMap<>();

        // put the host IP in the map
        map.put(ConsumerConfig
                    .BOOTSTRAP_SERVERS_CONFIG,
                "127.0.0.1:9092");

        // put the group ID of consumer in the map
        map.put(ConsumerConfig
                    .GROUP_ID_CONFIG,
                "id");
        map.put(ConsumerConfig
                    .KEY_DESERIALIZER_CLASS_CONFIG,
                StringDeserializer.class);
        map.put(ConsumerConfig
                    .VALUE_DESERIALIZER_CLASS_CONFIG,
                JsonDeserializer.class);

        // return message in JSON formate
        return new DefaultKafkaConsumerFactory<>(
            map, new StringDeserializer(),
            new JsonDeserializer<>(Student.class));
    }

    @Bean
    public ConcurrentKafkaListenerContainerFactory<String,
                                                   Student>
    studentListner()
    {
        ConcurrentKafkaListenerContainerFactory<String,
                                                Student>
            factory
            = new ConcurrentKafkaListenerContainerFactory<>();
        factory.setConsumerFactory(studentConsumer());
        return factory;
    }
}

@Service
public class KafkaService {

    // Annotation required to listen
    // the message from Kafka server
    @KafkaListener(topics = "JsonTopic",
                   groupId = "id", containerFactory
                                   = "studentListner")
    public void
    publish(Student student)
    {
        System.out.println("New Entry: "
                           + student);
    }
}