I am trying to learn Kafka and now Avro, To keep consistency between the sender object and receiver object, we keep a JSON schema (.avsc). but I am not able to find any simple example of how to use it. some example is using confluent (is confluent mandate for Avro), some are generating object via Avro tool. so far I have a working Kafka setup.
Object class
package com.example.kafka;
public class Hello {
String name;
String age;
public Hello(String name, String age) {
this.name = name;
this.age = age;
}
@Override
public String toString() {
return "Hello{" +
"name='" + name + '\'' +
", date='" + age + '\'' +
'}';
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
}
Controler Class
package com.example.kafka;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
@RequestMapping("/")
class KafkaController {
@Autowired
KafkaService kafkaService;
@GetMapping("test")
public Hello hello() {
Hello hello = new Hello("shrikant", "25");
kafkaService.hello(hello);
return hello;
}
}
Main Application
package com.example.kafka;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
@EnableAutoConfiguration
public class KafkaDemoApplication {
public static void main(String[] args) {
SpringApplication.run(KafkaDemoApplication.class, args);
}
}
KafkaProducerConfig
package com.example.kafka;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.common.serialization.StringSerializer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.kafka.core.DefaultKafkaProducerFactory;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.kafka.core.ProducerFactory;
import java.util.HashMap;
import java.util.Map;
@Configuration
public class KafkaProducerConfig {
@Bean
public Map<String, Object> producerConfigs() {
Map<String, Object> props = new HashMap<>();
props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, KafkaSerializer.class);
return props;
}
@Bean
public ProducerFactory<String, Hello> producerFactory() {
return new DefaultKafkaProducerFactory<>(producerConfigs());
}
@Bean
public KafkaTemplate<String, Hello> kafkaTemplate() {
return new KafkaTemplate<>(producerFactory());
}
}
KafkaSerializer
package com.example.kafka;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.apache.kafka.common.serialization.Serializer;
import java.util.Map;
public class KafkaSerializer implements Serializer<Hello> {
@Override
public byte[] serialize(String arg0, Hello developer) {
byte[] serializedBytes = null;
ObjectMapper objectMapper = new ObjectMapper();
try {
serializedBytes = objectMapper.writeValueAsString(developer).getBytes();
} catch (Exception e) {
e.printStackTrace();
}
return serializedBytes;
}
@Override
public void close() {
// TODO Auto-generated method stub
}
@Override
public void configure(Map<String, ?> arg0, boolean arg1) {
// TODO Auto-generated method stub
}
}
KafkaService
package com.example.kafka;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.stereotype.Service;
@Service
public class KafkaService {
@Autowired
private KafkaTemplate<String, Hello> kafkaTemplate;
public void hello(Hello hello) {
kafkaTemplate.send("test", hello);
}
}
Hello.avsc
{"namespace": "com.example.kafka",
"type": "record",
"name": "Hello",
"fields": [
{"name": "name", "type": "string"},
{"name": "age", "type": "string"},
]
}
build.gradle
buildscript {
repositories {
mavenCentral()
}
dependencies {
classpath 'org.springframework.boot:spring-boot-gradle-plugin:1.5.21.RELEASE'
}
}
plugins {
id 'java'
}
apply plugin: 'org.springframework.boot'
group = 'com.example.kafka'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '1.8'
repositories {
mavenCentral()
}
ext {
set('spring-kafka.version', "2.2.8.RELEASE")
}
dependencies {
compile 'org.springframework.boot:spring-boot-starter'
compile 'org.springframework.kafka:spring-kafka'
implementation 'org.springframework.boot:spring-boot-starter-web'
}
it's working setup and I am able to send and receive data, what changes I need to make in order to get Avro working.
