The Binder SPI consists of a number of interfaces, out-of-the box utility classes, and discovery strategies that provide a pluggable mechanism for connecting to external middleware.spring-doc.cn

The key point of the SPI is the Binder interface, which is a strategy for connecting inputs and outputs to external middleware. The following listing shows the definition of the Binder interface:spring-doc.cn

public interface Binder<T, C extends ConsumerProperties, P extends ProducerProperties> {
    Binding<T> bindConsumer(String bindingName, String group, T inboundBindTarget, C consumerProperties);

    Binding<T> bindProducer(String bindingName, T outboundBindTarget, P producerProperties);
}

The interface is parameterized, offering a number of extension points:spring-doc.cn

  • Input and output bind targets.spring-doc.cn

  • Extended consumer and producer properties, allowing specific Binder implementations to add supplemental properties that can be supported in a type-safe manner.spring-doc.cn

A typical binder implementation consists of the following:spring-doc.cn

  • A class that implements the Binder interface;spring-doc.cn

  • A Spring @Configuration class that creates a bean of type Binder along with the middleware connection infrastructure.spring-doc.cn

  • A META-INF/spring.binders file found on the classpath containing one or more binder definitions, as shown in the following example:spring-doc.cn

    kafka:\
org.springframework.cloud.stream.binder.kafka.config.KafkaBinderConfiguration
As it was mentioned earlier Binder abstraction is also one of the extension points of the framework. So if you can’t find a suitable binder in the preceding list you can implement your own binder on top of Spring Cloud Stream. In the How to create a Spring Cloud Stream Binder from scratch post a community member documents in details, with an example, a set of steps necessary to implement a custom binder. The steps are also highlighted in the Implementing Custom Binders section.
As it was mentioned earlier Binder abstraction is also one of the extension points of the framework. So if you can’t find a suitable binder in the preceding list you can implement your own binder on top of Spring Cloud Stream. In the How to create a Spring Cloud Stream Binder from scratch post a community member documents in details, with an example, a set of steps necessary to implement a custom binder. The steps are also highlighted in the Implementing Custom Binders section.