ReactiveReactive Revolution — RSocket

Reference from?: https://app.pluralsight.com/library/courses/allthetalks-session-68/table-of-contents

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.6.4</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>service</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>service</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>11</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-r2dbc</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-rsocket</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-webflux</artifactId>
</dependency>
<dependency>
<groupId>io.r2dbc</groupId>
<artifactId>r2dbc-postgresql</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>io.projectreactor</groupId>
<artifactId>reactor-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>

<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<excludes>
<exclude>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</exclude>
</excludes>
</configuration>
</plugin>
</plugins>
</build>

</project>

MainApp.java

package com.example.service;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.event.ApplicationReadyEvent;
import org.springframework.context.annotation.Bean;
import org.springframework.context.event.EventListener;
import org.springframework.data.annotation.Id;
import org.springframework.data.repository.reactive.ReactiveCrudRepository;
import org.springframework.messaging.handler.annotation.MessageMapping;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Controller;
import org.springframework.web.reactive.function.server.RouterFunction;
import org.springframework.web.reactive.function.server.ServerResponse;
import reactor.core.publisher.Flux;

import java.time.Duration;
import java.time.Instant;
import java.util.function.Supplier;
import java.util.stream.Stream;

import static org.springframework.web.reactive.function.server.RouterFunctions.route;

@SpringBootApplication
public class ServiceApplication {

public static void main(String[] args) {
SpringApplication.run(ServiceApplication.class, args);
}


@Bean
public RouterFunction<ServerResponse> routes(ReservationRepository rr) {
return route()
.GET("/reservations", request -> ServerResponse.ok().body(rr.findAll(), Reservation.class))
.build();
}
}

@Component
class SampleDataInit {
@Autowired
private ReservationRepository reservationRepository;

@EventListener(ApplicationReadyEvent.class)
public void go() {
Flux<Reservation> reservationFlux = Flux.just("Neha", "Aravind", "Laxmi", "Rajesh", "Anosh", "Sam", "Alex")
.map(name -> Reservation.builder().name(name).build())
.flatMap(r -> this.reservationRepository.save(r));

this.reservationRepository.deleteAll()
.thenMany(reservationFlux)
.thenMany(this.reservationRepository.findAll())
.subscribe(System.out::println);

}
}

interface ReservationRepository extends ReactiveCrudRepository<Reservation, Integer> {

}


@AllArgsConstructor
@NoArgsConstructor
@Builder
@Data
class Reservation {
@Id
private Integer id;
private String name;
}

@Controller
class GreetingService {

@MessageMapping("greetings")
Flux<GreetingResponse> greet(GreetingRequest request) {
return Flux.fromStream(Stream.generate(() ->
new GreetingResponse("Hello " + request.getName() + " @ " + Instant.now().toString())))
.delayElements(Duration.ofSeconds(1));
}

}

@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
class GreetingRequest {
private String name;
}

@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
class GreetingResponse {
private String message;
}

application.properties

spring.r2dbc.url=r2dbc:postgresql://localhost:5432/postgres
spring.r2dbc.username=postgres
spring.r2dbc.password=postgres
spring.rsocket.server.port=7070

init.sql

-- Drop table

-- DROP TABLE public.reservation;

CREATE TABLE public.reservation (
id serial4 NOT NULL,
"name" varchar NOT NULL
);

— — — — — RSocket

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.6.4</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>client</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>client</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>11</java.version>
<spring-cloud.version>2021.0.1</spring-cloud.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-rsocket</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-webflux</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-circuitbreaker-reactor-resilience4j</artifactId>
</dependency>

<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>io.projectreactor</groupId>
<artifactId>reactor-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>${spring-cloud.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>

<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<excludes>
<exclude>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</exclude>
</excludes>
</configuration>
</plugin>
</plugins>
</build>

</project>

application.properties

#server.port=9090

spring.main.web-application-type=none

MainApp.java

package com.example.client;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.extern.log4j.Log4j2;
import org.springframework.boot.ApplicationRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.messaging.rsocket.RSocketRequester;
import org.springframework.web.reactive.function.client.WebClient;
import reactor.core.publisher.Flux;

import java.io.IOException;
import java.time.Duration;

@Log4j2
@SpringBootApplication
public class ClientApplication {

public static void main(String[] args) throws IOException {
SpringApplication.run(ClientApplication.class, args);
System.in.read();
}

@Bean
WebClient http(WebClient.Builder builder) {
return builder.build();
}

@Bean
RSocketRequester rSocket(RSocketRequester.Builder builder) {
return builder.tcp("localhost", 7070);
}

@Bean
ApplicationRunner httpClient(WebClient http) {
return args -> {
http
.get()
.uri("http://localhost:8080/reservations")
.retrieve()
.bodyToFlux(Reservation.class)
.map(r -> r.getName())
.onErrorResume(ex -> Flux.just("EEKK!"))
.retry()
.timeout(Duration.ofSeconds(1))
.subscribe(log::info);
};
}

@Bean
public ApplicationRunner rSocketClient(RSocketRequester rSocketRequester) {
return args -> {
rSocketRequester.route("greetings")
.data(new GreetingRequest("All the Talks"))
.retrieveFlux(GreetingResponse.class)
.subscribe(log::info);
};
}
}

@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
class GreetingRequest {
private String name;
}

@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
class GreetingResponse {
private String message;
}

@AllArgsConstructor
@NoArgsConstructor
@Builder
@Data
class Reservation {
private Integer id;
private String name;
}

When you run the client, please make sure your service class is also up & running.

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