Add support for Spring Cloud Gateway MVC

[mraible]

Overview of the feature request

When we first integrated Spring Cloud Gateway, it only supported WebFlux. Now it supports Spring MVC, so we should try to support it too.

https://docs.spring.io/spring-cloud-gateway/reference/spring-cloud-gateway-server-mvc.html

Motivation for or Use Case

If you're developing microservices with Spring MVC, you might prefer MVC in your gateway too.

Related issues or PR

• Checking this box is mandatory (this is just to show you read everything)

[mshima]

There is no support for service discovery yet.

[mshima]

I was able to get service discovery working when I wrote this blog post back in December.

There is no support for spring.cloud.gateway.discovery.locator.enabled=true
So this does not work:

generator-jhipster/generators/server/templates/src/main/resources/config/application.yml.ejs

Lines 194 to 206 in 1d0a1c2

	discovery:
	locator:
	enabled: true
	lower-case-service-id: true
	predicates:
	- name: Path
	args:
	pattern: "'/services/'+serviceId.toLowerCase()+'/**'"
	filters:
	- name: RewritePath
	args:
	regexp: "'/services/' + serviceId.toLowerCase() + '/(?<remaining>.*)'"
	replacement: "'/${remaining}'"

Routes needs to be manually configured.

[mraible]

Confirmed: spring-cloud/spring-cloud-gateway#3332

[mshima]

Gateway is reactive by default it’s possible to force it imperative by setting reactive false or --no-reactive.

Issues:

• openapi generated server url is wrong in microservices.
• JwtTokenRelay needs to be implemented.

Maybe we should require --experimental flag.

[DanielFran]

Yes, we should add the --experimental flag.

[mshima]

Do I have to specify reactive false for the gateway?

Yes

[mshima]

@mraible following #25817 the routes option accepts "route", "route:host" or "route:host:port".
Updated jdl with routes option:

application {
  config {
    baseName gateway
    reactive false
    packageName org.jhipster.gateway
    applicationType gateway
    authenticationType oauth2
    buildTool gradle
    clientFramework react
    prodDatabaseType postgresql
    serviceDiscoveryType consul
    testFrameworks [cypress]
    microfrontends [blog, store]
    routes ["blog:blog:8081", "store:store:8082"]
  }
}

application {
  config {
    baseName blog
    reactive false
    packageName org.jhipster.blog
    applicationType microservice
    authenticationType oauth2
    buildTool gradle
    clientFramework react
    databaseType neo4j
    enableHibernateCache false
    serverPort 8081
    serviceDiscoveryType consul
    testFrameworks [cypress]
  }
  entities Blog, Post, Tag
}

application {
  config {
    baseName store
    reactive false
    packageName org.jhipster.store
    applicationType microservice
    authenticationType oauth2
    buildTool gradle
    clientFramework react
    databaseType mongodb
    enableHibernateCache false
    serverPort 8082
    serviceDiscoveryType consul
    testFrameworks [cypress]
  }
  entities Product
}

entity Blog {
  name String required minlength(3)
  handle String required minlength(2)
}

entity Post {
  title String required
  content TextBlob required
  date Instant required
}

entity Tag {
  name String required minlength(2)
}

entity Product {
  title String required
  price BigDecimal required min(0)
  image ImageBlob
}

relationship ManyToOne {
  Blog{user(login)} to User with builtInEntity
  Post{blog(name)} to Blog
}

relationship ManyToMany {
  Post{tag(name)} to Tag{post}
}

paginate Post, Tag with infinite-scroll
paginate Product with pagination

deployment {
  deploymentType docker-compose
  serviceDiscoveryType consul
  appsFolders [gateway, blog, store]
  dockerRepositoryName "mraible"
}

deployment {
  deploymentType kubernetes
  appsFolders [gateway, blog, store]
  clusteredDbApps [store]
  kubernetesNamespace demo
  kubernetesUseDynamicStorage true
  kubernetesStorageClassName ""
  serviceDiscoveryType consul
  dockerRepositoryName "mraible"
}

[mraible]

@mshima This seems like quite a few changes for a feature that might go away once Spring Cloud Gateway MVC supports it. However, I talked with the Gateway project lead and he said service discovery won't be GA until November, so we should probably implement this workaround until then.

[mshima]

This could be reused for #21012, otherwise we should just close it.

[mraible]

@egvimo Would this solution work to solve #21012?

[egvimo]

Yes, this would work, I think.

[mshima]

Upstream issues:

• MVC Server: Options to create routes automatically from service registry spring-cloud/spring-cloud-gateway#3332: support manually added routes.
• Required Gobalfilter type interface in Spring Cloud Gateway MVC, and instead of bean creation properties level routes configuration spring-cloud/spring-cloud-gateway#3382: duplicate required filters in every route
• X-Forwarded-Prefix not working when using MVC spring-cloud/spring-cloud-gateway#3354: manually set X-Forwarded-Prefix.
• Add support for MVC Server actuator spring-cloud/spring-cloud-gateway#3233: retrieve routes based on Add support for MVC Server actuator spring-cloud/spring-cloud-gateway#3233 (comment)