Make base path configurable for WebFlux applications

This commit adds the `"spring.webflux.base-path"` configuration
property. Configuring this property will gather all `HttpHandlers` into
a single composite and prefix all requests with a shared base path.

Closes gh-10129

Author: bclozel

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/reactive/HttpHandlerAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,9 @@
 
 package org.springframework.boot.autoconfigure.web.reactive;
 
+import java.util.Collections;
+import java.util.Map;
+
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.AutoConfigureOrder;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
@@ -26,7 +29,9 @@
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.Ordered;
+import org.springframework.http.server.reactive.ContextPathCompositeHandler;
 import org.springframework.http.server.reactive.HttpHandler;
+import org.springframework.util.StringUtils;
 import org.springframework.web.reactive.DispatcherHandler;
 import org.springframework.web.server.adapter.WebHttpHandlerBuilder;
 
@@ -55,8 +60,13 @@ public AnnotationConfig(ApplicationContext applicationContext) {
 		}
 
 		@Bean
-		public HttpHandler httpHandler() {
-			return WebHttpHandlerBuilder.applicationContext(this.applicationContext).build();
+		public HttpHandler httpHandler(WebFluxProperties properties) {
+			HttpHandler httpHandler = WebHttpHandlerBuilder.applicationContext(this.applicationContext).build();
+			if (StringUtils.hasText(properties.getBasePath())) {
+				Map<String, HttpHandler> handlersMap = Collections.singletonMap(properties.getBasePath(), httpHandler);
+				return new ContextPathCompositeHandler(handlersMap);
+			}
+			return httpHandler;
 		}
 
 	}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/reactive/WebFluxProperties.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,6 +17,7 @@
 package org.springframework.boot.autoconfigure.web.reactive;
 
 import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.util.StringUtils;
 
 /**
  * {@link ConfigurationProperties properties} for Spring WebFlux.
@@ -27,6 +28,11 @@
 @ConfigurationProperties(prefix = "spring.webflux")
 public class WebFluxProperties {
 
+	/**
+	 * Base path for all web handlers.
+	 */
+	private String basePath;
+
 	/**
 	 * Date format to use. For instance, `dd/MM/yyyy`.
 	 */
@@ -37,6 +43,27 @@ public class WebFluxProperties {
 	 */
 	private String staticPathPattern = "/**";
 
+	public String getBasePath() {
+		return basePath;
+	}
+
+	public void setBasePath(String basePath) {
+		this.basePath = cleanBasePath(basePath);
+	}
+
+	private String cleanBasePath(String basePath) {
+		String candidate = StringUtils.trimWhitespace(basePath);
+		if (StringUtils.hasText(candidate)) {
+			if (!candidate.startsWith("/")) {
+				candidate = "/" + candidate;
+			}
+			if (candidate.endsWith("/")) {
+				candidate = candidate.substring(0, candidate.length() - 1);
+			}
+		}
+		return candidate;
+	}
+
 	public String getDateFormat() {
 		return this.dateFormat;
 	}

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/reactive/HttpHandlerAutoConfigurationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,12 +16,14 @@
 
 package org.springframework.boot.autoconfigure.web.reactive;
 
+import org.assertj.core.api.InstanceOfAssertFactories;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.test.context.runner.ReactiveWebApplicationContextRunner;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.http.server.reactive.ContextPathCompositeHandler;
 import org.springframework.http.server.reactive.HttpHandler;
 import org.springframework.web.reactive.function.server.RouterFunction;
 import org.springframework.web.reactive.function.server.ServerResponse;
@@ -56,6 +58,18 @@ void shouldConfigureHttpHandlerAnnotation() {
 				.run((context) -> assertThat(context).hasSingleBean(HttpHandler.class));
 	}
 
+	@Test
+	void shouldConfigureBasePathCompositeHandler() {
+		this.contextRunner.withConfiguration(AutoConfigurations.of(WebFluxAutoConfiguration.class))
+				.withPropertyValues("spring.webflux.base-path=/something").run((context) -> {
+					assertThat(context).hasSingleBean(HttpHandler.class);
+					HttpHandler httpHandler = context.getBean(HttpHandler.class);
+					assertThat(httpHandler).isInstanceOf(ContextPathCompositeHandler.class)
+							.extracting("handlerMap", InstanceOfAssertFactories.map(String.class, HttpHandler.class))
+							.containsKey("/something");
+				});
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	static class CustomHttpHandler {
 

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/reactive/WebFluxPropertiesTests.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2012-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.autoconfigure.web.reactive;
+
+import java.util.Collections;
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.context.properties.bind.Bindable;
+import org.springframework.boot.context.properties.bind.Binder;
+import org.springframework.boot.context.properties.source.ConfigurationPropertySource;
+import org.springframework.boot.context.properties.source.MapConfigurationPropertySource;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link WebFluxProperties}
+ *
+ * @author Brian Clozel
+ */
+class WebFluxPropertiesTests {
+
+	private final WebFluxProperties properties = new WebFluxProperties();
+
+	@Test
+	void shouldPrefixBasePathWithMissingSlash() {
+		bind("spring.webflux.base-path", "something");
+		assertThat(this.properties.getBasePath()).isEqualTo("/something");
+	}
+
+	@Test
+	void shouldRemoveTrailingSlashFromBasePath() {
+		bind("spring.webflux.base-path", "/something/");
+		assertThat(this.properties.getBasePath()).isEqualTo("/something");
+	}
+
+	private void bind(String name, String value) {
+		bind(Collections.singletonMap(name, value));
+	}
+
+	private void bind(Map<String, String> map) {
+		ConfigurationPropertySource source = new MapConfigurationPropertySource(map);
+		new Binder(source).bind("spring.webflux", Bindable.ofInstance(this.properties));
+	}
+
+}