Let's see the following application.yml configuration file for a microservice:

spring:
  application:
    name: customer-service
  cloud:
    stream:
      kafka:
        binder:
          brokers:
          - localhost:9092
      bindings:
          notification-in:
            destination: notification
            contentType: application/json
          notification-out:
            destination: notification
            contentType: application/json 

As you can see, this file configures the address of the Kafka server to connect to, and the Kafka topic we use for both the inbound and outbound streams in our code. The contentType properties tell Spring Cloud Stream to send or receive our message objects as strings in the streams.