Multiple Binders on the Classpath

When multiple binders are present on the classpath, the application must indicate which binder is to be used for each destination binding. Each binder configuration contains a META-INF/spring.binders file, which is a simple properties file, as shown in the following example:

Similar files exist for the other provided binder implementations (such as Kafka), and custom binder implementations are expected to provide them as well. The key represents an identifying name for the binder implementation, whereas the value is a comma-separated list of configuration classes that each contain one and only one bean definition of type org.springframework.cloud.stream.binder.Binder.

Binder selection can either be performed globally, using the spring.cloud.stream.defaultBinder property (for example, spring.cloud.stream.defaultBinder=rabbit) or individually, by configuring the binder on each binding. For instance, a processor application (that has bindings named input and output for read and write respectively) that reads from Kafka and writes to RabbitMQ can specify the following configuration: