#998 - WebMvcHateoasConfiguration now delays a beans-of-type lookup.

We now delay the lookup of RepresentationModelProcessor instances in WebMvcHateoasConfiguration so that the BeanPostProcessor registered does now not trigger eager initialization of downstream beans.

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

@@ -47,6 +47,7 @@ import com.fasterxml.jackson.databind.ObjectMapper;
  * Spring MVC HATEOAS Configuration
  *
  * @author Greg Turnquist
+ * @author Oliver Drotbohm
  */
 @Configuration
 class WebMvcHateoasConfiguration {
@@ -59,10 +60,16 @@ class WebMvcHateoasConfiguration {
 	}
 
 	@Bean
-	HypermediaRepresentationModelBeanProcessorPostProcessor hypermediaRepresentionModelProcessorConfigurator(
+	RepresentationModelProcessorInvoker representationModelProcessorInvoker(
 			List<RepresentationModelProcessor<?>> processors) {
+		return new RepresentationModelProcessorInvoker(processors);
+	}
 
-		return new HypermediaRepresentationModelBeanProcessorPostProcessor(processors);
+	@Bean
+	static HypermediaRepresentationModelBeanProcessorPostProcessor hypermediaRepresentionModelProcessorConfigurator(
+			ObjectProvider<RepresentationModelProcessorInvoker> invoker) {
+
+		return new HypermediaRepresentationModelBeanProcessorPostProcessor(invoker);
 	}
 
 	@Bean
@@ -107,12 +114,18 @@ class WebMvcHateoasConfiguration {
 
 	/**
 	 * @author Greg Turnquist
+	 * @author Oliver Drotbohm
 	 */
 	@RequiredArgsConstructor
 	static class HypermediaRepresentationModelBeanProcessorPostProcessor implements BeanPostProcessor {
 
-		private final List<RepresentationModelProcessor<?>> processors;
+		private final ObjectProvider<RepresentationModelProcessorInvoker> invoker;
 
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.beans.factory.config.BeanPostProcessor#postProcessAfterInitialization(java.lang.Object, java.lang.String)
+		 */
+		@NonNull
 		@Override
 		public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
 
@@ -124,7 +137,7 @@ class WebMvcHateoasConfiguration {
 				delegate.addHandlers(adapter.getReturnValueHandlers());
 
 				RepresentationModelProcessorHandlerMethodReturnValueHandler handler = new RepresentationModelProcessorHandlerMethodReturnValueHandler(
-						delegate, new RepresentationModelProcessorInvoker(processors));
+						delegate, () -> invoker.getObject());
 
 				adapter.setReturnValueHandlers(Collections.singletonList(handler));
 			}

src/main/java/org/springframework/hateoas/server/mvc/RepresentationModelProcessorHandlerMethodReturnValueHandler.java

@@ -20,6 +20,7 @@ import lombok.RequiredArgsConstructor;
 
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
+import java.util.function.Supplier;
 
 import org.springframework.core.MethodParameter;
 import org.springframework.core.ResolvableType;
@@ -60,7 +61,7 @@ public class RepresentationModelProcessorHandlerMethodReturnValueHandler impleme
 	}
 
 	private final @NonNull HandlerMethodReturnValueHandler delegate;
-	private final @NonNull RepresentationModelProcessorInvoker invoker;
+	private final @NonNull Supplier<RepresentationModelProcessorInvoker> invoker;
 
 	private boolean rootLinksAsHeaders = false;
 
@@ -122,7 +123,7 @@ public class RepresentationModelProcessorHandlerMethodReturnValueHandler impleme
 			targetType = returnValueType;
 		}
 
-		RepresentationModel<?> result = invoker.invokeProcessorsFor((RepresentationModel) value, targetType);
+		RepresentationModel<?> result = invoker.get().invokeProcessorsFor((RepresentationModel) value, targetType);
 		delegate.handleReturnValue(rewrapResult(result, returnValue), returnType, mavContainer, webRequest);
 	}
 

src/test/java/org/springframework/hateoas/server/mvc/ResourceProcessorHandlerMethodReturnValueHandlerUnitTest.java

@@ -18,6 +18,7 @@ package org.springframework.hateoas.server.mvc;
 import static java.util.Collections.*;
 import static org.assertj.core.api.Assertions.*;
 import static org.mockito.ArgumentMatchers.*;
+import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.*;
 import static org.springframework.util.ReflectionUtils.*;
 
@@ -253,7 +254,7 @@ class ResourceProcessorHandlerMethodReturnValueHandlerUnitTest {
 		MethodParameter parameter = METHOD_PARAMS.get("resource");
 
 		RepresentationModelProcessorHandlerMethodReturnValueHandler handler = new RepresentationModelProcessorHandlerMethodReturnValueHandler(
-				delegate, new RepresentationModelProcessorInvoker(resourceProcessors));
+				delegate, () -> new RepresentationModelProcessorInvoker(resourceProcessors));
 		handler.setRootLinksAsHeaders(true);
 		handler.handleReturnValue(mapper.apply(resource), parameter, null, null);
 
@@ -299,7 +300,7 @@ class ResourceProcessorHandlerMethodReturnValueHandlerUnitTest {
 		resourceProcessors.add((RepresentationModelProcessor<?>) factory.getProxy());
 
 		new RepresentationModelProcessorHandlerMethodReturnValueHandler(delegate,
-				new RepresentationModelProcessorInvoker(resourceProcessors));
+				() -> new RepresentationModelProcessorInvoker(resourceProcessors));
 	}
 
 	/**
@@ -322,7 +323,7 @@ class ResourceProcessorHandlerMethodReturnValueHandlerUnitTest {
 		}
 
 		HandlerMethodReturnValueHandler handler = new RepresentationModelProcessorHandlerMethodReturnValueHandler(delegate,
-				new RepresentationModelProcessorInvoker(resourceProcessors));
+				() -> new RepresentationModelProcessorInvoker(resourceProcessors));
 		handler.handleReturnValue(returnValue, methodParam, null, null);
 
 		verify(delegate, times(1)).handleReturnValue(expected, methodParam, null, null);
@@ -334,7 +335,7 @@ class ResourceProcessorHandlerMethodReturnValueHandlerUnitTest {
 		when(delegate.supportsReturnType(Mockito.any(MethodParameter.class))).thenReturn(value);
 
 		HandlerMethodReturnValueHandler handler = new RepresentationModelProcessorHandlerMethodReturnValueHandler(delegate,
-				new RepresentationModelProcessorInvoker(resourceProcessors));
+				() -> new RepresentationModelProcessorInvoker(resourceProcessors));
 
 		assertThat(handler.supportsReturnType(parameter)).isEqualTo(value);
 	}