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Consumer contracts

The service enforces jEAP messaging consumer contracts at startup. Each Kafka message type configured in messages.json must have a matching consumer contract registered for the application.

Generating contracts​

Consumer contracts are generated at compile time by placing the @JeapMessageConsumerContractsByTemplates annotation on any class in the service instance module. The annotation processor reads messages.json and generates one consumer contract per configured message type:

@JeapMessageConsumerContractsByTemplates(
    appName = "my-opensearch-index-writer"
)
@SpringBootApplication
public class MyOpenSearchIndexWriterApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyOpenSearchIndexWriterApplication.class, args);
    }
}

The annotation is processed by jeap-messaging-contract-annotation-processor, which is pulled in transitively through the jeap-opensearch-index-writer-service-instance dependency.

Annotation attributes​

AttributeDescription
appNameLogical application name used for the consumer contracts. Defaults to spring.application.name from application.yml when not set. Must match spring.application.name exactly.

Startup validation​

On startup, the service verifies that a consumer contract exists for every message type listed in messages.json. If the annotation is absent, or if the resolved appName does not match spring.application.name, the service refuses to start with a NoContractException.