I want to establish a communication between a client and server application using Springs new reactive webflux extension.
For dependency management I use gradle. My build.gradle file on the server, as well as on the client side basically is:
buildscript {
repositories {
mavenCentral()
maven { url "https://repo.spring.io/snapshot" }
}
dependencies {
classpath("org.springframework.boot:spring-boot-gradle-plugin:2.0.0.BUILD-SNAPSHOT")
}
}
repositories {
mavenCentral()
maven { url "https://repo.spring.io/snapshot" }
}
apply plugin: 'java'
apply plugin: 'org.springframework.boot'
apply plugin: "io.spring.dependency-management"
dependencies {
compile("org.springframework.boot:spring-boot-starter-webflux")
}
(It should be noted that 2.0.0.BUILD-SNAPSHOT is a moving target and the problem at hand may just vanish one day due to changes inside the dependency)
When I start the server side application everything starts up well, including the start of an embedded netty server.
But when start the client application also a netty server is started, causing a "java.net.BindException: Address already in use", because the clientside netty server listens on the same port as the serverside netty server.
My question is: Why is netty started on the client side in the first place and how can I prevent it?
According to the Spring-Boot Documentation Spring tries to determine if Web support is required and configures the Spring Application context accordingly.
And according to the Docs this can be overridden by a call to setWebEnvironment(false). My client startup code then looks like:
@SpringBootApplication(scanBasePackages = { "com.tatics.flux.main" })
public class Client {
public static void main(String[] args) throws Exception {
SpringApplication app = new SpringApplication(Client.class);
app.setWebEnvironment(false);
app.run(Client.class, args);
WebClient webClient = WebClient.create();
Mono<String> result = webClient
.post()
.uri("http://localhost:8080/fluxService")
// This does not work any more: .body("Hallo")
// and must be replaced by:
.body(BodyInserters.fromObject("Hallo"))
.accept(MediaType.TEXT_PLAIN)
.exchange()
.flatMap(response -> response.bodyToMono(String.class));
}
}
Unfortunately netty is still started. Also I note that setWebEnvironment(false) is marked as deprecated.
Any help on how to prevent netty from starting but otherwise preserve all webflux-dependencies is appreciated.
Here is an excerpt from the auto-configuration Report:
=========================
AUTO-CONFIGURATION REPORT
=========================
Positive matches:
-----------------
...
ReactiveWebServerAutoConfiguration matched:
- found ReactiveWebApplicationContext (OnWebApplicationCondition)
ReactiveWebServerAutoConfiguration#defaultReactiveWebServerCustomizer matched:
- @ConditionalOnMissingBean (types: org.springframework.boot.autoconfigure.web.reactive.DefaultReactiveWebServerCustomizer; SearchStrategy: all) did not find any beans (OnBeanCondition)
ReactiveWebServerConfiguration.ReactorNettyAutoConfiguration matched:
- @ConditionalOnClass found required class 'reactor.ipc.netty.http.server.HttpServer'; @ConditionalOnMissingClass did not find unwanted class (OnClassCondition)
- @ConditionalOnMissingBean (types: org.springframework.boot.web.reactive.server.ReactiveWebServerFactory; SearchStrategy: all) did not find any beans (OnBeanCondition)
ReactorCoreAutoConfiguration matched:
- @ConditionalOnClass found required classes 'reactor.core.publisher.Mono', 'reactor.core.publisher.Flux'; @ConditionalOnMissingClass did not find unwanted class (OnClassCondition)
...
Negative matches:
-----------------
...
ReactiveWebServerConfiguration.JettyAutoConfiguration:
Did not match:
- @ConditionalOnClass did not find required class 'org.eclipse.jetty.server.Server' (OnClassCondition)
ReactiveWebServerConfiguration.TomcatAutoConfiguration:
Did not match:
- @ConditionalOnClass did not find required class 'org.apache.catalina.startup.Tomcat' (OnClassCondition)
ReactiveWebServerConfiguration.UndertowAutoConfiguration:
Did not match:
- @ConditionalOnClass did not find required class 'io.undertow.Undertow' (OnClassCondition)
...
ReactiveWebServerConfiguration.JettyAutoConfiguration:
Did not match:
- @ConditionalOnClass did not find required class 'org.eclipse.jetty.server.Server' (OnClassCondition)
ReactiveWebServerConfiguration.TomcatAutoConfiguration:
Did not match:
- @ConditionalOnClass did not find required class 'org.apache.catalina.startup.Tomcat' (OnClassCondition)
ReactiveWebServerConfiguration.UndertowAutoConfiguration:
Did not match:
- @ConditionalOnClass did not find required class 'io.undertow.Undertow' (OnClassCondition)
The main issue with your code is that you're currently creating a SpringApplication, then you customize it - to finally drop everything and run the static method run(Object primarySource, String... args).
The following should work:
@SpringBootApplication
public class Client {
public static void main(String[] args) throws Exception {
SpringApplication app = new SpringApplication(Client.class);
app.setWebApplicationType(WebApplicationType.NONE);
app.run(args);
}
@Bean
public CommandLineRunner myCommandLineRunner() {
return args -> {
// we have to block here, since command line runners don't
// consume reactive types and simply return after the execution
String result = WebClient.create("http://localhost:8080")
.post()
.uri("/fluxService")
.body("Hallo")
.accept(MediaType.TEXT_PLAIN)
.retrieve()
.bodyToMono(String.class)
.block();
// print the result?
};
}
}
If not, please run your application using the --debug flag and add to your question the relevant parts of the auto-configuration report, especially the auto-configurations dealing with servers.