Update WelcomePageHandlerMapping to handle reqs with no Accept header

Closes gh-7138

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/WebMvcAutoConfiguration.java

@@ -61,6 +61,7 @@ import org.springframework.format.datetime.DateFormatter;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.util.StringUtils;
 import org.springframework.validation.DefaultMessageCodesResolver;
 import org.springframework.validation.MessageCodesResolver;
 import org.springframework.web.accept.ContentNegotiationManager;
@@ -516,8 +517,7 @@ public class WebMvcAutoConfiguration {
 
 		@Override
 		public Object getHandlerInternal(HttpServletRequest request) throws Exception {
-			for (MediaType mediaType : MediaType
-					.parseMediaTypes(request.getHeader(HttpHeaders.ACCEPT))) {
+			for (MediaType mediaType : getAcceptedMediaTypes(request)) {
 				if (mediaType.includes(MediaType.TEXT_HTML)) {
 					return super.getHandlerInternal(request);
 				}
@@ -525,6 +525,12 @@ public class WebMvcAutoConfiguration {
 			return null;
 		}
 
+		private List<MediaType> getAcceptedMediaTypes(HttpServletRequest request) {
+			String acceptHeader = request.getHeader(HttpHeaders.ACCEPT);
+			return MediaType.parseMediaTypes(
+					StringUtils.hasText(acceptHeader) ? acceptHeader : "*/*");
+		}
+
 	}
 
 }

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/WebMvcAutoConfigurationTests.java

@@ -577,7 +577,7 @@ public class WebMvcAutoConfigurationTests {
 	}
 
 	@Test
-	public void welcomePageMappingOnlyHandlesRequestsThatAcceptTextHtml()
+	public void welcomePageMappingDoesNotHandleRequestThatDoNotAcceptTextHtml()
 			throws Exception {
 		load("spring.resources.static-locations:classpath:/welcome-page/");
 		assertThat(this.context.getBeansOfType(WelcomePageHandlerMapping.class))
@@ -587,6 +587,27 @@ public class WebMvcAutoConfigurationTests {
 				.andExpect(status().isNotFound());
 	}
 
+	@Test
+	public void welcomePageMappingHandlesRequestsWithNoAcceptHeader() throws Exception {
+		load("spring.resources.static-locations:classpath:/welcome-page/");
+		assertThat(this.context.getBeansOfType(WelcomePageHandlerMapping.class))
+				.hasSize(1);
+		MockMvc mockMvc = MockMvcBuilders.webAppContextSetup(this.context).build();
+		mockMvc.perform(get("/")).andExpect(status().isOk())
+				.andExpect(forwardedUrl("index.html"));
+	}
+
+	@Test
+	public void welcomePageMappingHandlesRequestsWithEmptyAcceptHeader()
+			throws Exception {
+		load("spring.resources.static-locations:classpath:/welcome-page/");
+		assertThat(this.context.getBeansOfType(WelcomePageHandlerMapping.class))
+				.hasSize(1);
+		MockMvc mockMvc = MockMvcBuilders.webAppContextSetup(this.context).build();
+		mockMvc.perform(get("/").header(HttpHeaders.ACCEPT, ""))
+				.andExpect(status().isOk()).andExpect(forwardedUrl("index.html"));
+	}
+
 	@Test
 	public void welcomePageMappingWorksWithNoTrailingSlashOnResourceLocation()
 			throws Exception {