#1080 - Improved configuration setup and documentation on EntityLinks.

We now explicitly only enable EntityLinks in WebMVC environments. This is also now reflected properly in the reference documentation.

Author: odrotbohm

src/main/asciidoc/server.adoc

@@ -267,6 +267,10 @@ curl -v localhost:8080/employees \
 [[server.entity-links]]
 == [[fundamentals.obtaining-links.entity-links]] Using the EntityLinks interface
 
+IMPORTANT: `EntityLinks` and it's various implementations are NOT currently provided out-of-the-box for Spring WebFlux applications.
+The contract defined in the `EntityLinks` SPI was originally aimed at Spring Web MVC and doesn't consider Reactor types.
+Developing a comparable contract that supports reactive programming is still in progress.
+
 So far, we have created links by pointing to the web-framework implementations (that is, the Spring MVC controllers) and inspected the mapping.
 In many cases, these classes essentially read and write representations backed by a model class.
 
@@ -285,13 +289,13 @@ Link link = links.linkToItemResource(Customer.class, 1L);
 
 `EntityLinks` is available via dependency injection by activating `@EnableHypermediaSupprt` in your Spring MVC configuration.
 This will cause a variety of default implementations of `EntityLinks` being registered.
-The most fundamental one is `ControllerEntityLinks` that inspects SpringMVC and Spring WebFlux controller classes.
+The most fundamental one is `ControllerEntityLinks` that inspects SpringMVC controller classes.
 If you want to register your own implementation of `EntityLinks`, check out <<server.entity-links.spi, this section>>.
 
 [[server.entity-links.controller]]
-=== EntityLinks based on Spring MVC and WebFlux controllers
+=== EntityLinks based on Spring MVC controllers
 
-Activating entity links functionality causes all the Spring MVC and WebFlux controllers available in the current `ApplicationContext` to be inspected for the `@ExposesResourceFor(…)` annotation.
+Activating entity links functionality causes all the Spring MVC controllers available in the current `ApplicationContext` to be inspected for the `@ExposesResourceFor(…)` annotation.
 The annotation exposes which model type the controller manages.
 Beyond that, we assume that you adhere to following the URI mapping setup and conventions:
 
@@ -421,10 +425,6 @@ It's registered as primary bean so that it's always the sole injection candidate
 `ControllerEntityLinks` is the default implementation that will be included in the setup, but users are free to implement and register their own implementations.
 Making those available to the `EntityLinks` instance available for injection is a matter of registering your implementation as Spring bean.
 
-IMPORTANT: `EntityLinks` and it's various implementations are NOT currently provided out-of-the-box for Spring WebFlux applications.
-The contract defined in the `EntityLinks` SPI was originally aimed at Spring Web MVC and doesn't consider Reactor types.
-Developing a comparable contract that supports reactive programming is still in progress.
-
 .Declaring a custom EntityLinks implementation
 ====
 [source, java]

src/main/java/org/springframework/hateoas/config/HateoasConfiguration.java

@@ -28,7 +28,6 @@
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.context.annotation.Import;
 import org.springframework.context.annotation.Primary;
 import org.springframework.context.support.AbstractMessageSource;
 import org.springframework.context.support.ReloadableResourceBundleMessageSource;
@@ -58,7 +57,6 @@
  * @since 0.19
  */
 @Configuration
-@Import(EntityLinksConfiguration.class)
 @EnablePluginRegistries({ LinkDiscoverer.class })
 public class HateoasConfiguration {
 

src/main/java/org/springframework/hateoas/config/WebMvcEntityLinksConfiguration.java

@@ -30,7 +30,7 @@
  * @author Oliver Gierke
  */
 @Configuration
-class WebMvcEntityLinksConfiguration {
+class WebMvcEntityLinksConfiguration extends EntityLinksConfiguration {
 
 	@Bean
 	ControllerEntityLinksFactoryBean webMvcEntityLinks(ObjectProvider<WebMvcLinkBuilderFactory> linkBuilderFactory) {

src/test/java/org/springframework/hateoas/config/WebStackImportSelectorUnitTest.java

@@ -18,9 +18,12 @@
 import static org.assertj.core.api.Assertions.*;
 
 import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.NoSuchBeanDefinitionException;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.core.type.AnnotationMetadata;
-import org.springframework.core.type.StandardAnnotationMetadata;
 import org.springframework.hateoas.config.EnableHypermediaSupport.HypermediaType;
+import org.springframework.hateoas.server.EntityLinks;
 import org.springframework.hateoas.support.WebStack;
 
 /**
@@ -35,7 +38,7 @@ class WebStackImportSelectorUnitTest {
 	@Test // #973
 	void activatesAllWebStacksByDefault() {
 
-		AnnotationMetadata metadata = new StandardAnnotationMetadata(DefaultHypermedia.class);
+		AnnotationMetadata metadata = AnnotationMetadata.introspect(DefaultHypermedia.class);
 
 		assertThat(selector.selectImports(metadata))
 				.containsExactlyInAnyOrderElementsOf(WebStackImportSelector.CONFIGS.values());
@@ -44,29 +47,39 @@ void activatesAllWebStacksByDefault() {
 	@Test // #973
 	void activatesWebMvcOnlyifConfigured() {
 
-		AnnotationMetadata metadata = new StandardAnnotationMetadata(WebMvcHypermedia.class);
+		AnnotationMetadata metadata = AnnotationMetadata.introspect(WebMvcHypermedia.class);
 
 		assertThat(selector.selectImports(metadata)).containsExactly(WebStackImportSelector.CONFIGS.get(WebStack.WEBMVC));
 	}
 
 	@Test // #973
 	void activatesWebFluxOnlyIfConfigured() {
 
-		AnnotationMetadata metadata = new StandardAnnotationMetadata(WebFluxHypermedia.class);
+		AnnotationMetadata metadata = AnnotationMetadata.introspect(WebFluxHypermedia.class);
 
 		assertThat(selector.selectImports(metadata)).containsExactly(WebStackImportSelector.CONFIGS.get(WebStack.WEBFLUX));
 	}
 
 	@Test // #973
 	void rejectsNoStacksSelected() {
 
-		AnnotationMetadata metadata = new StandardAnnotationMetadata(NoStacksHypermedia.class);
+		AnnotationMetadata metadata = AnnotationMetadata.introspect(NoStacksHypermedia.class);
 
 		assertThatExceptionOfType(IllegalStateException.class) //
 				.isThrownBy(() -> selector.selectImports(metadata)) //
 				.withMessageContaining(NoStacksHypermedia.class.getName());
 	}
 
+	@Test // #1080
+	void noEntityLinksRegisteredForWebFluxBootstrap() throws Exception {
+
+		try (ConfigurableApplicationContext context = new AnnotationConfigApplicationContext(WebFluxHypermedia.class)) {
+
+			assertThatExceptionOfType(NoSuchBeanDefinitionException.class) //
+					.isThrownBy(() -> context.getBean(EntityLinks.class));
+		}
+	}
+
 	@EnableHypermediaSupport(type = HypermediaType.HAL)
 	static class DefaultHypermedia {}