spring-reactive-redis-messaging

Example project showing how to interact with Redis using Spring Boot

HowTo

Inspired by https://spring.io/guides/gs/spring-data-reactive-redis/

Go to https://start.spring.io/ and choose Lombok, Reactive Web, Reactive Redis.

The Testcase CoffeeControllerTest.java uses testcontainers framework to leverage redis as a broker. Just run it, testcontainers will take care of firing up redis with Docker (just be sure to have Docker installed).

If you want to run the SpringredisApplication.java be sure to fire up redis with:

docker-compose up

Implementing Reactive Messaging with Redis

See https://docs.spring.io/spring-data/data-redis/docs/2.1.1.RELEASE/reference/html/#redis:reactive

ReactiveRedisConnectionFactory

First we´ll need to configure Spring to connect reactively to Redis with the ReactiveRedisConnectionFactory with Lettuce behind the scenes:

    @Bean
    public ReactiveRedisConnectionFactory connectionFactory() {
        return new LettuceConnectionFactory("localhost", 6379);
    }

ReactiveRedisTemplate

Interaction with Redis in reactive use cases is abstracted in Spring Data by ReactiveRedisTemplate. So we need to initialize a Bean:

    @Bean
    public ReactiveRedisTemplate<String, String> reactiveRedisTemplate(ReactiveRedisConnectionFactory factory) {
        return new ReactiveRedisTemplate<>(factory, RedisSerializationContext.string());
    }

Have a look into Redis PubSub

Only if one uses channels and subscribes to it on Redis, these channels are present (see Understanding channels in https://redisgreen.net/blog/pubsub-howto/).

To see the current channels in the Redis Docker container, check:

docker exec -it redisContainerName sh

redis-cli

pubsub channels

REST endpoints

Spring Reactive WebClient: https://docs.spring.io/spring/docs/current/spring-framework-reference/testing.html#webtestclient-tests

We need to use a curl / Postman / httpie to open up a HTTP connection to retrieve Server Side Events (SSE) from our channel subscriber:

curl -v http://localhost:8080/message/coffees

Now messages could be retrieved from the Redis Pub/Sub channel coffees:queue.

On a second terminal windows we can now publish messages to Redis :

http POST http://localhost:8080/message/coffee/fooBarCoffee

See https://developer.okta.com/blog/2018/09/24/reactive-apis-with-spring-webflux#the-web-the-final-frontier for more details on how to implement Spring Webflux style REST endpoints.

Links

Redis

https://github.com/eugenp/tutorials/blob/master/persistence-modules/spring-data-redis/src/test/java/com/baeldung/spring/data/reactive/redis/template/RedisTemplateListOpsIntegrationTest.java

https://spring.io/guides/gs/messaging-redis/

https://www.baeldung.com/spring-data-redis-pub-sub

Redis Reactive Messaging

https://spring.io/guides/gs/spring-data-reactive-redis/

https://docs.spring.io/spring-data/data-redis/docs/2.1.1.RELEASE/reference/html/#redis:reactive

https://www.baeldung.com/java-redis-lettuce

RabbitMQ / AMQP Messaging

https://www.baeldung.com/spring-amqp-reactive

Reactive WebFlux Stack

https://developer.okta.com/blog/2018/09/24/reactive-apis-with-spring-webflux#the-web-the-final-frontier

https://spring.io/guides/gs/reactive-rest-service/

https://www.baeldung.com/spring-5-webclient

https://docs.spring.io/spring/docs/current/spring-framework-reference/testing.html#webtestclient-tests

https://dzone.com/articles/reactive-programming-with-spring-webflux

https://www.baeldung.com/spring-5-functional-web

https://medium.com/@cheron.antoine/tuto-building-a-reactive-restful-api-with-spring-webflux-java-258fd4dbae41

https://stackoverflow.com/questions/50740795/how-to-wait-for-all-requests-to-complete-with-spring-5-webclient