无法反序列化来自 kafka 主题的 json 字符串，该主题在蛇案例中具有属性

Question

Him

I am not able to deserialize a json string coming from kafka topic. Attributes are in mix of snake case and camel case structure, for example: input:

{
"event_type" : "ABC",
"user_id" : 1567221,
"name" : "HGHAAAB" //here no snake case
"user_contact" : "12345678",
"phoneNumber" : "91222"
} 

Now I want to create Request DTO on my side like below:

public class KafkaRequest { 
private String eventType;
private int userId;
private String name; 
private String userContact;
private String phoneNumber;

//getters and setters

} 

Can any one suggest what should be the correct way? I tried creating CustomNameStrategy and deserializing with ObjectMapper.readValue() but it did not work.

Thanks is advance!!!

Answer 1

If you are using jackson you can either use @JsonProperty 6.1. @JsonProperty

@JsonProperty("event_type")
private String eventType;

Or you can set property PropertyNamingStrategy.SNAKE_CASE to ObjectMapper

objectMapper.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);

Answer 2

You can use GSON there are way to define field name strategy

Gson gson = new GsonBuilder().disableHtmlEscaping().setFieldNamingStrategy(FieldNamingPolicy.UPPER_CAMEL_CASE_WITH_SPACES).create();

or even u can define custom as well

Gson gson = new GsonBuilder().disableHtmlEscaping().setFieldNamingStrategy(new FieldNamingStrategy() {
            @Override
            public String translateName(Field f) {
                return f.getName().toLowerCase(); //or any logic
            }
        }).create();

For Producer just StringSerializer will work

properties.setProperty(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());
properties.setProperty(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());

Assume you already have populated POJO say kafkaRequest then you can publish

ProducerRecord producerRecord = new ProducerRecord<String, String>("topicName", null, gson.toJson(kafkaRequest));

On Consumer side parse back to POJO

properties.setProperty("key.deserializer", StringDeserializer.class.getName());
properties.setProperty("value.deserializer", StringDeserializer.class.getName());
KafkaConsumer<String, String> consumer = new KafkaConsumer<String, String>(properties);
while (true) {
    ConsumerRecords<String, String> records = consumer.poll(100);
    for (ConsumerRecord<String, String> record : records) {
         KafkaRequest kafkaRequest = gson.fromJson(record.value(), KafkaRequest.class);
    }
}