I am trying to retrieve value from application.yml. The final line below is showing kafkaConfig as null, and cannot read. How do I setup the Kafka Config and code properly, to read from the json file? We are using @Data instead of getters/setters.

KafkaConfig.java

@Configuration
@ConfigurationProperties("kafka")
@Data
public class KafkaConfig {
    private String topic;
    private String event;
}

Application.yml

kafka:
  topic: "testTopic"
  event: "testEvent"

KafkaProducerBeans.java

@Component
public class KafkaProducerBeans {

    @Autowired
    private KafkaConfig kafkaConfig;

    public KafkaProducerBeans(KafkaConfig kafkaConfig) {
        this.kafkaConfig = kafkaConfig;
    }

    @Bean(name = "kafkaTestClient")
    public String getData() {
        return kafkaConfig.getTopic();  // final line is creating null for kafka Config
    }

Resource: https://codingnconcepts.com/spring-boot/spring-configuration-properties-using-yml/

CodePudding user response：

I think the recommended way of binding properties to pojos is to use the @EnableConfigurationProperties annotation like so:

KafkaConfig.java

@ConfigurationProperties("kafka")
@Data
public class KafkaConfig {
    private String topic;
    private String event;
}

KafkaProducerBeans.java

@Component
@EnableConfigurationProperties(KafkaConfig.class)
public class KafkaProducerBeans {

    private final KafkaConfig kafkaConfig;

    @Autowired
    public KafkaProducerBeans(KafkaConfig kafkaConfig) {
        this.kafkaConfig = kafkaConfig;
    }

    // [...]
}

Refer to the official Spring Documentation for further details:

• https://docs.spring.io/spring-boot/docs/current/reference/html/features.html#features.external-config.typesafe-configuration-properties.java-bean-binding
• https://docs.spring.io/spring-boot/docs/current/reference/html/features.html#features.external-config.typesafe-configuration-properties.enabling-annotated-types

CodePudding user response：

Add one more annotation @EnableConfigurationProperties on the class KafkaConfig

KafkaConfig.java

@Configuration
@EnableConfigurationProperties    // new added annotation
@ConfigurationProperties("kafka")
@Data
public class KafkaConfig {
    private String topic;
    private String event;
}

CodePudding user response：

@ComponentScan(basePackages ="PATH" )

PATH: the package path you want it to look for

@ComponentScan(basePackages ="PATH" )
@Configuration
@Import(value = {
    KafkaProducerBeans.class
})
public class AppConfig{

}