Add Http2 configuration properties

This commit adds a new configuration properties class for configuring
HTTP/2 protocol support.
By default, this protocol is disabled as enabling it requires several
manual changes:

* configuring a web server for proper TLS and ALPN support
* configuring a proper SSL certificate

See gh-10043

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

@@ -31,6 +31,7 @@ import java.util.TimeZone;
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.boot.context.properties.NestedConfigurationProperty;
 import org.springframework.boot.web.server.Compression;
+import org.springframework.boot.web.server.Http2;
 import org.springframework.boot.web.server.Ssl;
 import org.springframework.boot.web.servlet.server.Jsp;
 import org.springframework.util.Assert;
@@ -102,6 +103,9 @@ public class ServerProperties {
 	@NestedConfigurationProperty
 	private Compression compression = new Compression();
 
+	@NestedConfigurationProperty
+	private Http2 http2 = new Http2();
+
 	private Servlet servlet = new Servlet();
 
 	private final Tomcat tomcat = new Tomcat();
@@ -190,6 +194,10 @@ public class ServerProperties {
 		return this.compression;
 	}
 
+	public Http2 getHttp2() {
+		return this.http2;
+	}
+
 	public Servlet getServlet() {
 		return this.servlet;
 	}

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

@@ -55,6 +55,9 @@ public class DefaultReactiveWebServerCustomizer implements
 		if (this.serverProperties.getCompression() != null) {
 			server.setCompression(this.serverProperties.getCompression());
 		}
+		if (this.serverProperties.getHttp2() != null) {
+			server.setHttp2(this.serverProperties.getHttp2());
+		}
 	}
 
 }

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

@@ -120,6 +120,9 @@ public class DefaultServletWebServerFactoryCustomizer
 		if (this.serverProperties.getCompression() != null) {
 			factory.setCompression(this.serverProperties.getCompression());
 		}
+		if (this.serverProperties.getHttp2() != null) {
+			factory.setHttp2(this.serverProperties.getHttp2());
+		}
 		factory.setServerHeader(this.serverProperties.getServerHeader());
 		if (factory instanceof TomcatServletWebServerFactory) {
 			TomcatCustomizer.customizeTomcat(this.serverProperties, this.environment,

spring-boot-project/spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -165,6 +165,7 @@ content into your application; rather pick only the properties that you need.
 	server.error.include-stacktrace=never # When to include a "stacktrace" attribute.
 	server.error.path=/error # Path of the error controller.
 	server.error.whitelabel.enabled=true # Enable the default error page displayed in browsers in case of a server error.
+	server.http2.enabled=true # Enable HTTP/2 support if the current environment supports it.
 	server.jetty.acceptors= # Number of acceptor threads to use.
 	server.jetty.accesslog.append=false # Append to log.
 	server.jetty.accesslog.date-format=dd/MMM/yyyy:HH:mm:ss Z # Timestamp format of the request log.

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/server/AbstractConfigurableWebServerFactory.java

@@ -50,6 +50,8 @@ public class AbstractConfigurableWebServerFactory
 
 	private SslStoreProvider sslStoreProvider;
 
+	private Http2 http2;
+
 	private Compression compression;
 
 	private String serverHeader;
@@ -134,6 +136,15 @@ public class AbstractConfigurableWebServerFactory
 		this.sslStoreProvider = sslStoreProvider;
 	}
 
+	public Http2 getHttp2() {
+		return this.http2;
+	}
+
+	@Override
+	public void setHttp2(Http2 http2) {
+		this.http2 = http2;
+	}
+
 	public Compression getCompression() {
 		return this.compression;
 	}

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/server/ConfigurableWebServerFactory.java

@@ -62,6 +62,12 @@ public interface ConfigurableWebServerFactory
 	 */
 	void setSslStoreProvider(SslStoreProvider sslStoreProvider);
 
+	/**
+	 * Sets the HTTP/2 configuration that will be applied to the server.
+	 * @param http2 the HTTP/2 configuration
+	 */
+	void setHttp2(Http2 http2);
+
 	/**
 	 * Sets the compression configuration that will be applied to the server's default
 	 * connector.

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/server/Http2.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2012-2017 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
+ *
+ *      http://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.web.server;
+
+/**
+ * Simple server-independent abstraction for HTTP/2 configuration.
+ *
+ * @author Brian Clozel
+ * @since 2.0.0
+ */
+public class Http2 {
+
+	/**
+	 * If HTTP/2 protocol is enabled.
+	 */
+	private boolean enabled = false;
+
+	public boolean getEnabled() {
+		return this.enabled;
+	}
+
+	public void setEnabled(boolean enabled) {
+		this.enabled = enabled;
+	}
+}