Polish “Allow connection timeout to be configured via the environment”

 - Preserve default connection timeout when server.connection-timeout
   has not been set
 - Apply standard coding conventions and formatting

See gh-6072

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

@@ -30,7 +30,6 @@ import javax.servlet.SessionCookieConfig;
 import javax.servlet.SessionTrackingMode;
 import javax.validation.constraints.NotNull;
 
-import io.undertow.Undertow;
 import io.undertow.Undertow.Builder;
 import io.undertow.UndertowOptions;
 import org.apache.catalina.Context;
@@ -40,11 +39,11 @@ import org.apache.catalina.valves.RemoteIpValve;
 import org.apache.coyote.AbstractProtocol;
 import org.apache.coyote.ProtocolHandler;
 import org.apache.coyote.http11.AbstractHttp11Protocol;
+import org.eclipse.jetty.server.AbstractConnector;
 import org.eclipse.jetty.server.ConnectionFactory;
 import org.eclipse.jetty.server.Handler;
 import org.eclipse.jetty.server.HttpConfiguration;
 import org.eclipse.jetty.server.Server;
-import org.eclipse.jetty.server.ServerConnector;
 import org.eclipse.jetty.server.handler.ContextHandler;
 import org.eclipse.jetty.server.handler.HandlerCollection;
 import org.eclipse.jetty.server.handler.HandlerWrapper;
@@ -148,11 +147,11 @@ public class ServerProperties
 	private int maxHttpPostSize = 0; // bytes
 
 	/**
-	 * The number of milliseconds connectors will wait for another HTTP request before closing the connection.
-	 * The default value is to use the value that has been set for the connectionTimeout attribute.
-	 * Use a value of -1 to indicate no (i.e. infinite) timeout.
+	 * Time in milliseconds that connectors will wait for another HTTP request before
+	 * closing the connection. When not set, the connector's container-specific default
+	 * will be used. Use a value of -1 to indicate no (i.e. infinite) timeout.
 	 */
-	private int connectionTimeout = -1;
+	private Integer connectionTimeout;
 
 	private Session session = new Session();
 
@@ -375,11 +374,11 @@ public class ServerProperties
 		return (platform == null ? false : platform.isUsingForwardHeaders());
 	}
 
-	public int getConnectionTimeout() {
-		return connectionTimeout;
+	public Integer getConnectionTimeout() {
+		return this.connectionTimeout;
 	}
 
-	public void setConnectionTimeout(final int connectionTimeout) {
+	public void setConnectionTimeout(Integer connectionTimeout) {
 		this.connectionTimeout = connectionTimeout;
 	}
 
@@ -786,14 +785,19 @@ public class ServerProperties
 			if (getUriEncoding() != null) {
 				factory.setUriEncoding(getUriEncoding());
 			}
-			customizeConnectionTimeout(serverProperties, factory);
+			if (serverProperties.getConnectionTimeout() != null) {
+				customizeConnectionTimeout(factory,
+						serverProperties.getConnectionTimeout());
+			}
 		}
 
-		private void customizeConnectionTimeout(final ServerProperties serverProperties, final TomcatEmbeddedServletContainerFactory factory) {
+		private void customizeConnectionTimeout(
+				TomcatEmbeddedServletContainerFactory factory, int connectionTimeout) {
 			for (Connector connector : factory.getAdditionalTomcatConnectors()) {
 				if (connector.getProtocolHandler() instanceof AbstractProtocol) {
-					final AbstractProtocol handler = (AbstractProtocol) connector.getProtocolHandler();
-					handler.setConnectionTimeout(serverProperties.getConnectionTimeout());
+					AbstractProtocol<?> handler = (AbstractProtocol<?>) connector
+							.getProtocolHandler();
+					handler.setConnectionTimeout(connectionTimeout);
 				}
 			}
 		}
@@ -1006,7 +1010,7 @@ public class ServerProperties
 		}
 
 		void customizeJetty(final ServerProperties serverProperties,
-							JettyEmbeddedServletContainerFactory factory) {
+				JettyEmbeddedServletContainerFactory factory) {
 			factory.setUseForwardHeaders(serverProperties.getOrDeduceUseForwardHeaders());
 			if (this.acceptors != null) {
 				factory.setAcceptors(this.acceptors);
@@ -1022,17 +1026,23 @@ public class ServerProperties
 				customizeMaxHttpPostSize(factory, serverProperties.getMaxHttpPostSize());
 			}
 
-			customizeConnectionTimeout(serverProperties, factory);
+			if (serverProperties.getConnectionTimeout() != null) {
+				customizeConnectionTimeout(factory,
+						serverProperties.getConnectionTimeout());
+			}
 		}
-		private void customizeConnectionTimeout(final ServerProperties serverProperties,
-													final JettyEmbeddedServletContainerFactory factory) {
+
+		private void customizeConnectionTimeout(
+				JettyEmbeddedServletContainerFactory factory,
+				final int connectionTimeout) {
 			factory.addServerCustomizers(new JettyServerCustomizer() {
 				@Override
-				public void customize(final Server server) {
-					for (org.eclipse.jetty.server.Connector connector : server.getConnectors()) {
-						if (connector instanceof ServerConnector) {
-							ServerConnector serverConnector = (ServerConnector) connector;
-							serverConnector.setIdleTimeout(serverProperties.getConnectionTimeout());
+				public void customize(Server server) {
+					for (org.eclipse.jetty.server.Connector connector : server
+							.getConnectors()) {
+						if (connector instanceof AbstractConnector) {
+							((AbstractConnector) connector)
+									.setIdleTimeout(connectionTimeout);
 						}
 					}
 				}
@@ -1193,7 +1203,7 @@ public class ServerProperties
 		}
 
 		void customizeUndertow(final ServerProperties serverProperties,
-								UndertowEmbeddedServletContainerFactory factory) {
+				UndertowEmbeddedServletContainerFactory factory) {
 			if (this.bufferSize != null) {
 				factory.setBufferSize(this.bufferSize);
 			}
@@ -1227,14 +1237,20 @@ public class ServerProperties
 				customizeMaxHttpPostSize(factory, serverProperties.getMaxHttpPostSize());
 			}
 
-			customizeConnectionTimeout(serverProperties, factory);
+			if (serverProperties.getConnectionTimeout() != null) {
+				customizeConnectionTimeout(factory,
+						serverProperties.getConnectionTimeout());
+			}
 		}
-		private void customizeConnectionTimeout(final ServerProperties serverProperties,
-													final UndertowEmbeddedServletContainerFactory factory) {
+
+		private void customizeConnectionTimeout(
+				UndertowEmbeddedServletContainerFactory factory,
+				final int connectionTimeout) {
 			factory.addBuilderCustomizers(new UndertowBuilderCustomizer() {
 				@Override
 				public void customize(Builder builder) {
-					builder.setSocketOption(UndertowOptions.NO_REQUEST_TIMEOUT, serverProperties.getConnectionTimeout());
+					builder.setSocketOption(UndertowOptions.NO_REQUEST_TIMEOUT,
+							connectionTimeout);
 				}
 			});
 		}

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

@@ -149,6 +149,7 @@ content into your application; rather pick only the properties that you need.
 	server.compression.excluded-user-agents= # List of user-agents to exclude from compression.
 	server.compression.mime-types= # Comma-separated list of MIME types that should be compressed. For instance `text/html,text/css,application/json`
 	server.compression.min-response-size= # Minimum response size that is required for compression to be performed. For instance 2048
+	server.connection-timeout= # Time in milliseconds that connectors will wait for another HTTP request before closing the connection. When not set, the connector's container-specific default will be used. Use a value of -1 to indicate no (i.e. infinite) timeout.
 	server.context-parameters.*= # Servlet context init parameters. For instance `server.context-parameters.a=alpha`
 	server.context-path= # Context path of the application.
 	server.display-name=application # Display name of the application.