Polish "Auto-configure templated welcome page"

Closes gh-10545

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/servlet/WelcomePageHandlerMapping.java

@@ -48,14 +48,15 @@ final class WelcomePageHandlerMapping extends AbstractUrlHandlerMapping {
 	WelcomePageHandlerMapping(TemplateAvailabilityProviders templateAvailabilityProviders,
 			ApplicationContext applicationContext, Optional<Resource> welcomePage,
 			String staticPathPattern) {
-		if (welcomeTemplateExists(templateAvailabilityProviders, applicationContext)) {
+		if (welcomePage.isPresent() && "/**".equals(staticPathPattern)) {
+			logger.info("Adding welcome page: " + welcomePage.get());
+			setRootViewName("forward:index.html");
+		}
+		else if (welcomeTemplateExists(templateAvailabilityProviders,
+				applicationContext)) {
 			logger.info("Adding welcome page template: index");
 			setRootViewName("index");
 		}
-		else if (welcomePage.isPresent() && "/**".equals(staticPathPattern)) {
-			logger.info("Adding welcome page: " + welcomePage);
-			setRootViewName("forward:index.html");
-		}
 	}
 
 	private boolean welcomeTemplateExists(

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/servlet/WelcomePageHandlerMappingTests.java

@@ -16,14 +16,21 @@
 
 package org.springframework.boot.autoconfigure.web.servlet;
 
+import java.util.Collections;
+import java.util.Map;
 import java.util.Optional;
 
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
 import org.junit.Test;
 
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration;
+import org.springframework.boot.autoconfigure.template.TemplateAvailabilityProvider;
+import org.springframework.boot.autoconfigure.template.TemplateAvailabilityProviders;
 import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
@@ -32,10 +39,15 @@ import org.springframework.core.io.FileSystemResource;
 import org.springframework.core.io.Resource;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
+import org.springframework.test.web.servlet.MockMvc;
 import org.springframework.test.web.servlet.setup.MockMvcBuilders;
+import org.springframework.web.servlet.ViewResolver;
+import org.springframework.web.servlet.view.AbstractView;
+import org.springframework.web.servlet.view.InternalResourceView;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.forwardedUrl;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
 
@@ -109,17 +121,55 @@ public class WelcomePageHandlerMappingTests {
 				.andExpect(status().isNotFound()));
 	}
 
+	@Test
+	public void handlesRequestForTemplateThatAcceptsTextHtml() {
+		this.contextRunner.withUserConfiguration(TemplateConfiguration.class)
+				.run((context) -> {
+					MockMvc mockMvc = MockMvcBuilders.webAppContextSetup(context).build();
+					mockMvc.perform(get("/").accept(MediaType.TEXT_HTML))
+							.andExpect(status().isOk())
+							.andExpect(content().string("index template"));
+				});
+	}
+
+	@Test
+	public void handlesRequestForTemplateThatAcceptsAll() {
+		this.contextRunner.withUserConfiguration(TemplateConfiguration.class)
+				.run((context) -> {
+					MockMvc mockMvc = MockMvcBuilders.webAppContextSetup(context).build();
+					mockMvc.perform(get("/").accept(MediaType.ALL))
+							.andExpect(status().isOk())
+							.andExpect(content().string("index template"));
+				});
+	}
+
+	@Test
+	public void prefersAStaticResourceToATemplate() {
+		this.contextRunner.withUserConfiguration(StaticResourceConfiguration.class,
+				TemplateConfiguration.class).run((context) -> {
+					MockMvc mockMvc = MockMvcBuilders.webAppContextSetup(context).build();
+					mockMvc.perform(get("/").accept(MediaType.ALL))
+							.andExpect(status().isOk())
+							.andExpect(forwardedUrl("index.html"));
+				});
+	}
+
 	@Configuration
 	static class HandlerMappingConfiguration {
 
 		@Bean
 		public WelcomePageHandlerMapping handlerMapping(
 				ApplicationContext applicationContext,
+				ObjectProvider<TemplateAvailabilityProviders> templateAvailabilityProviders,
 				ObjectProvider<Resource> staticIndexPage,
 				@Value("${static-path-pattern:/**}") String staticPathPattern) {
 			return new WelcomePageHandlerMapping(
+					templateAvailabilityProviders.getIfAvailable(
+							() -> new TemplateAvailabilityProviders(applicationContext)),
+					applicationContext,
 					Optional.ofNullable(staticIndexPage.getIfAvailable()),
 					staticPathPattern);
+
 		}
 
 	}
@@ -134,4 +184,43 @@ public class WelcomePageHandlerMappingTests {
 
 	}
 
+	@Configuration
+	static class TemplateConfiguration {
+
+		@Bean
+		public TemplateAvailabilityProviders templateAvailabilityProviders() {
+			return new TestTemplateAvailabilityProviders((view, environment, classLoader,
+					resourceLoader) -> view.equals("index"));
+		}
+
+		@Bean
+		public ViewResolver viewResolver() {
+			return (name, locale) -> {
+				if (name.startsWith("forward:")) {
+					return new InternalResourceView(name.substring("forward:".length()));
+				}
+				return new AbstractView() {
+
+					@Override
+					protected void renderMergedOutputModel(Map<String, Object> model,
+							HttpServletRequest request, HttpServletResponse response)
+									throws Exception {
+						response.getWriter().print(name + " template");
+					}
+
+				};
+			};
+		}
+
+	}
+
+	private static class TestTemplateAvailabilityProviders
+			extends TemplateAvailabilityProviders {
+
+		TestTemplateAvailabilityProviders(TemplateAvailabilityProvider provider) {
+			super(Collections.singletonList(provider));
+		}
+
+	}
+
 }

spring-boot-project/spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -1952,9 +1952,7 @@ By default, resources are mapped on `+/**+`, but you can tune that with the
 You can also customize the static resource locations by using the
 `spring.resources.static-locations` property (replacing the default values with a list of
 directory locations). The root Servlet context path `"/"` is automatically added as a
-location as well. If you do this, the default welcome page detection switches to your
+location as well.
-custom locations. So, if there is an `index.html` in any of your locations on startup, it
-is the home page of the application.
 
 In addition to the '`standard`' static resource locations mentioned earlier, a special
 case is made for http://www.webjars.org/[Webjars content]. Any resources with a path in
@@ -2022,6 +2020,13 @@ post] and in Spring Framework's
 {spring-reference}web.html#mvc-config-static-resources[reference documentation].
 ====
 
+[[boot-features-spring-mvc-welcome-page]]
+==== Welcome Page
+Spring Boot support both static and templated welcome pages. It first looks for an
+`index.html` file in the configured static content locations. If one is not found, it
+then looks for an `index` template. If either is found it is automatically used as the
+welcome page of the application.
+
 
 
 [[boot-features-spring-mvc-favicon]]