Netty HttpServer api changed/differs from available examples

Question

Netty server instantiation in Arjen Poutsma's blog post and Josh Long's video example is done by creating an reactor.ipc.netty.http.HttpServer instance and then calling it's start or startAndAwait method with an ReactorHttpHandlerAdapter instance as an argument.

However the API seems to have changed as now start and startAndAwait methods now expect a lambda with the following signature:

java.util.function.Function<? super reactor.ipc.netty.http.HttpChannel,? extends org.reactivestreams.Publisher<java.lang.Void>>

Project dependencies and their versions are the same as in Arjen Poutsma's example project

    <dependency>
        <groupId>org.reactivestreams</groupId>
        <artifactId>reactive-streams</artifactId>
        <version>1.0.0</version>
    </dependency>
    <dependency>
        <groupId>io.projectreactor</groupId>
        <artifactId>reactor-core</artifactId>
        <version>3.0.3.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>io.projectreactor.ipc</groupId>
        <artifactId>reactor-netty</artifactId>
        <version>0.5.2.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.apache.tomcat.embed</groupId>
        <artifactId>tomcat-embed-core</artifactId>
        <version>8.5.4</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-web-reactive</artifactId>
        <version>5.0.0.BUILD-SNAPSHOT</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.8.2</version>
    </dependency>

What is the new/proper way of instantiating a netty server with spring reactor support?

Yevhenii Melnyk · Accepted Answer · 2016-11-29 21:10:44Z

The recommended way to set up project for now is to use http://start.spring.io/ as Josh Long suggests in his video. This is because spring reactive is only release candidate now and we need compatible versions to run samples.This is achieved via adding this piece to code:

    <dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot.experimental</groupId>
            <artifactId>spring-boot-dependencies-web-reactive</artifactId>
            <version>0.1.0.BUILD-SNAPSHOT</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

According your question about HttpServer interface change, the minimal working example is the following:

import org.reactivestreams.Publisher;
import org.springframework.http.server.reactive.HttpHandler;
import org.springframework.http.server.reactive.ReactorHttpHandlerAdapter;
import org.springframework.web.reactive.function.RouterFunction;
import org.springframework.web.reactive.function.ServerRequest;
import org.springframework.web.reactive.function.ServerResponse;
import reactor.core.publisher.Mono;
import reactor.ipc.netty.http.server.HttpServer;

import java.io.IOException;

import static org.springframework.web.reactive.function.RequestPredicates.GET;
import static org.springframework.web.reactive.function.RouterFunctions.route;
import static org.springframework.web.reactive.function.RouterFunctions.toHttpHandler;

public class FunctionalReactiveServer {

    public static final String HOST = "localhost";
    public static final int PORT = 8080;

    public static void main(String[] args) throws InterruptedException, IOException {
        RouterFunction<?> route = route(GET("/sayHello"), FunctionalReactiveServer::sayHelloHandler);
        HttpHandler httpHandler = toHttpHandler(route);

        ReactorHttpHandlerAdapter adapter = new ReactorHttpHandlerAdapter(httpHandler);
        HttpServer server = HttpServer.create(HOST, PORT);
        server.newHandler(adapter).block();

        System.out.println("Press ENTER to exit.");
        System.in.read();
    }

    public static ServerResponse<Publisher<String>> sayHelloHandler(ServerRequest request) {
        return ServerResponse.ok().body(Mono.just("Hello!"), String.class);
    }

}

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