check for both Spring MVC and for Spring WebFlux when deciding to register the Integration Graph controller

[joshlong]

IntegrationGraphControllerRegistrarImportSelector checks for the DispatcherServlet, which fails in a Spring WebFlux application. I copied and pasted the relevant code to a separate class hiearchy, commented out the test for Spring MVC and then ran it in a Spring WebFlux app, and it seems to work.

[garyrussell]

Contributions are welcome 😄

[artembilan]

In the WebFlux module we use the code like:

	/**
	 * The {@code boolean} flag to indicate if the
	 * {@code org.springframework.web.reactive.result.method.RequestMappingInfo}
	 * is present in the CLASSPATH to allow to register the Integration server reactive components.
	 */
	public static final boolean WEB_FLUX_PRESENT =
			ClassUtils.isPresent("org.springframework.web.reactive.result.method.RequestMappingInfo",
					WebFluxContextUtils.class.getClassLoader());

to indicate that we are good to go with the WebFlux server components registration.

I don't think that we need to do one class in this webflux module.
I think as the fix there should be enough to add similar condition to the IntegrationGraphControllerRegistrarImportSelector:

if (HttpContextUtils.WEB_MVC_PRESENT || WEB_FLUX_PRESENT) {
	return new String[] { IntegrationGraphControllerRegistrar.class.getName() };
}

The JavaDocs of the @EnableIntegrationGraphController should be improved respectively.

That will work properly just because spring-integration-http is direct dependency of of the spring-integration-webflux.