Merge pull request #16342 Pascal Zwick

* pr/16342:
  Polish "Simplify the configuration of the ProtocolHandler"
  Simplify the configuration of the ProtocolHandler

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

@@ -28,6 +28,7 @@ import org.springframework.boot.web.embedded.jetty.JettyReactiveWebServerFactory
 import org.springframework.boot.web.embedded.netty.NettyReactiveWebServerFactory;
 import org.springframework.boot.web.embedded.tomcat.TomcatConnectorCustomizer;
 import org.springframework.boot.web.embedded.tomcat.TomcatContextCustomizer;
+import org.springframework.boot.web.embedded.tomcat.TomcatProtocolHandlerCustomizer;
 import org.springframework.boot.web.embedded.tomcat.TomcatReactiveWebServerFactory;
 import org.springframework.boot.web.embedded.undertow.UndertowReactiveWebServerFactory;
 import org.springframework.boot.web.reactive.server.ReactiveWebServerFactory;
@@ -76,12 +77,16 @@ abstract class ReactiveWebServerFactoryConfiguration {
 		@Bean
 		public TomcatReactiveWebServerFactory tomcatReactiveWebServerFactory(
 				ObjectProvider<TomcatConnectorCustomizer> connectorCustomizers,
-				ObjectProvider<TomcatContextCustomizer> contextCustomizers) {
+				ObjectProvider<TomcatContextCustomizer> contextCustomizers,
+				ObjectProvider<TomcatProtocolHandlerCustomizer<?>> protocolHandlerCustomizers) {
 			TomcatReactiveWebServerFactory factory = new TomcatReactiveWebServerFactory();
 			factory.getTomcatConnectorCustomizers().addAll(
 					connectorCustomizers.orderedStream().collect(Collectors.toList()));
 			factory.getTomcatContextCustomizers().addAll(
 					contextCustomizers.orderedStream().collect(Collectors.toList()));
+			factory.getTomcatProtocolHandlerCustomizers()
+					.addAll(protocolHandlerCustomizers.orderedStream()
+							.collect(Collectors.toList()));
 			return factory;
 		}
 

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

@@ -35,6 +35,7 @@ import org.springframework.boot.autoconfigure.condition.SearchStrategy;
 import org.springframework.boot.web.embedded.jetty.JettyServletWebServerFactory;
 import org.springframework.boot.web.embedded.tomcat.TomcatConnectorCustomizer;
 import org.springframework.boot.web.embedded.tomcat.TomcatContextCustomizer;
+import org.springframework.boot.web.embedded.tomcat.TomcatProtocolHandlerCustomizer;
 import org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory;
 import org.springframework.boot.web.embedded.undertow.UndertowServletWebServerFactory;
 import org.springframework.boot.web.servlet.server.ServletWebServerFactory;
@@ -66,12 +67,16 @@ class ServletWebServerFactoryConfiguration {
 		@Bean
 		public TomcatServletWebServerFactory tomcatServletWebServerFactory(
 				ObjectProvider<TomcatConnectorCustomizer> connectorCustomizers,
-				ObjectProvider<TomcatContextCustomizer> contextCustomizers) {
+				ObjectProvider<TomcatContextCustomizer> contextCustomizers,
+				ObjectProvider<TomcatProtocolHandlerCustomizer<?>> protocolHandlerCustomizers) {
 			TomcatServletWebServerFactory factory = new TomcatServletWebServerFactory();
 			factory.getTomcatConnectorCustomizers().addAll(
 					connectorCustomizers.orderedStream().collect(Collectors.toList()));
 			factory.getTomcatContextCustomizers().addAll(
 					contextCustomizers.orderedStream().collect(Collectors.toList()));
+			factory.getTomcatProtocolHandlerCustomizers()
+					.addAll(protocolHandlerCustomizers.orderedStream()
+							.collect(Collectors.toList()));
 			return factory;
 		}
 

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

@@ -23,6 +23,7 @@ import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.test.context.runner.ReactiveWebApplicationContextRunner;
 import org.springframework.boot.web.embedded.tomcat.TomcatConnectorCustomizer;
 import org.springframework.boot.web.embedded.tomcat.TomcatContextCustomizer;
+import org.springframework.boot.web.embedded.tomcat.TomcatProtocolHandlerCustomizer;
 import org.springframework.boot.web.embedded.tomcat.TomcatReactiveWebServerFactory;
 import org.springframework.boot.web.reactive.context.AnnotationConfigReactiveWebApplicationContext;
 import org.springframework.boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext;
@@ -131,6 +132,21 @@ public class ReactiveWebServerFactoryAutoConfigurationTests {
 		});
 	}
 
+	@Test
+	public void tomcatProtocolHandlerCustomizerBeanIsAddedToFactory() {
+		ReactiveWebApplicationContextRunner runner = new ReactiveWebApplicationContextRunner(
+				AnnotationConfigReactiveWebApplicationContext::new)
+						.withConfiguration(AutoConfigurations
+								.of(ReactiveWebServerFactoryAutoConfiguration.class))
+						.withUserConfiguration(
+								TomcatProtocolHandlerCustomizerConfiguration.class);
+		runner.run((context) -> {
+			TomcatReactiveWebServerFactory factory = context
+					.getBean(TomcatReactiveWebServerFactory.class);
+			assertThat(factory.getTomcatProtocolHandlerCustomizers()).hasSize(1);
+		});
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	protected static class HttpHandlerConfiguration {
 
@@ -193,4 +209,15 @@ public class ReactiveWebServerFactoryAutoConfigurationTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class TomcatProtocolHandlerCustomizerConfiguration {
+
+		@Bean
+		public TomcatProtocolHandlerCustomizer protocolHandlerCustomizer() {
+			return (protocolHandler) -> {
+			};
+		}
+
+	}
+
 }

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

@@ -32,6 +32,7 @@ import org.springframework.boot.test.context.runner.ContextConsumer;
 import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
 import org.springframework.boot.web.embedded.tomcat.TomcatConnectorCustomizer;
 import org.springframework.boot.web.embedded.tomcat.TomcatContextCustomizer;
+import org.springframework.boot.web.embedded.tomcat.TomcatProtocolHandlerCustomizer;
 import org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory;
 import org.springframework.boot.web.server.WebServerFactoryCustomizer;
 import org.springframework.boot.web.servlet.ServletRegistrationBean;
@@ -170,6 +171,21 @@ public class ServletWebServerFactoryAutoConfigurationTests {
 		});
 	}
 
+	@Test
+	public void tomcatProtocolHandlerCustomizerBeanIsAddedToFactory() {
+		WebApplicationContextRunner runner = new WebApplicationContextRunner(
+				AnnotationConfigServletWebServerApplicationContext::new)
+						.withConfiguration(AutoConfigurations
+								.of(ServletWebServerFactoryAutoConfiguration.class))
+						.withUserConfiguration(
+								TomcatProtocolHandlerCustomizerConfiguration.class);
+		runner.run((context) -> {
+			TomcatServletWebServerFactory factory = context
+					.getBean(TomcatServletWebServerFactory.class);
+			assertThat(factory.getTomcatProtocolHandlerCustomizers()).hasSize(1);
+		});
+	}
+
 	private ContextConsumer<AssertableWebApplicationContext> verifyContext() {
 		return this::verifyContext;
 	}
@@ -308,4 +324,15 @@ public class ServletWebServerFactoryAutoConfigurationTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class TomcatProtocolHandlerCustomizerConfiguration {
+
+		@Bean
+		public TomcatProtocolHandlerCustomizer protocolHandlerCustomizer() {
+			return (protocolHandler) -> {
+			};
+		}
+
+	}
+
 }

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/tomcat/ConfigurableTomcatWebServerFactory.java

@@ -68,6 +68,14 @@ public interface ConfigurableTomcatWebServerFactory extends ConfigurableWebServe
 	 */
 	void addContextCustomizers(TomcatContextCustomizer... tomcatContextCustomizers);
 
+	/**
+	 * Add {@link TomcatProtocolHandlerCustomizer}s that should be added to the Tomcat
+	 * {@link Connector}.
+	 * @param tomcatProtocolHandlerCustomizers the customizers to add
+	 */
+	void addProtocolHandlerCustomizers(
+			TomcatProtocolHandlerCustomizer<?>... tomcatProtocolHandlerCustomizers);
+
 	/**
 	 * Set the character encoding to use for URL decoding. If not specified 'UTF-8' will
 	 * be used.

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/tomcat/TomcatProtocolHandlerCustomizer.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2012-2019 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.web.embedded.tomcat;
+
+import org.apache.catalina.connector.Connector;
+import org.apache.coyote.ProtocolHandler;
+
+/**
+ * Callback interface that can be used to customize the {@link ProtocolHandler} on the
+ * {@link Connector}.
+ *
+ * @param <T> specified type for customization based on {@link ProtocolHandler}
+ * @author Pascal Zwick
+ * @see ConfigurableTomcatWebServerFactory
+ * @since 2.2.0
+ */
+@FunctionalInterface
+public interface TomcatProtocolHandlerCustomizer<T extends ProtocolHandler> {
+
+	/**
+	 * Customize the protocol handler.
+	 * @param protocolHandler the protocol handler to customize
+	 */
+	void customize(T protocolHandler);
+
+}

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/tomcat/TomcatReactiveWebServerFactory.java

@@ -34,9 +34,11 @@ import org.apache.catalina.core.AprLifecycleListener;
 import org.apache.catalina.loader.WebappLoader;
 import org.apache.catalina.startup.Tomcat;
 import org.apache.coyote.AbstractProtocol;
+import org.apache.coyote.ProtocolHandler;
 import org.apache.coyote.http2.Http2Protocol;
 import org.apache.tomcat.util.scan.StandardJarScanFilter;
 
+import org.springframework.boot.util.LambdaSafe;
 import org.springframework.boot.web.reactive.server.AbstractReactiveWebServerFactory;
 import org.springframework.boot.web.reactive.server.ReactiveWebServerFactory;
 import org.springframework.boot.web.server.WebServer;
@@ -72,6 +74,8 @@ public class TomcatReactiveWebServerFactory extends AbstractReactiveWebServerFac
 
 	private List<TomcatConnectorCustomizer> tomcatConnectorCustomizers = new ArrayList<>();
 
+	private List<TomcatProtocolHandlerCustomizer<?>> tomcatProtocolHandlerCustomizers = new ArrayList<>();
+
 	private String protocol = DEFAULT_PROTOCOL;
 
 	private Charset uriEncoding = DEFAULT_CHARSET;
@@ -168,6 +172,7 @@ public class TomcatReactiveWebServerFactory extends AbstractReactiveWebServerFac
 		if (connector.getProtocolHandler() instanceof AbstractProtocol) {
 			customizeProtocol((AbstractProtocol<?>) connector.getProtocolHandler());
 		}
+		invokeProtocolHandlerCustomizers(connector);
 		if (getUriEncoding() != null) {
 			connector.setURIEncoding(getUriEncoding().name());
 		}
@@ -184,6 +189,15 @@ public class TomcatReactiveWebServerFactory extends AbstractReactiveWebServerFac
 		}
 	}
 
+	@SuppressWarnings("unchecked")
+	private void invokeProtocolHandlerCustomizers(Connector connector) {
+		ProtocolHandler protocolHandler = connector.getProtocolHandler();
+		LambdaSafe
+				.callbacks(TomcatProtocolHandlerCustomizer.class,
+						this.tomcatProtocolHandlerCustomizers, protocolHandler)
+				.invoke((customizer) -> customizer.customize(protocolHandler));
+	}
+
 	private void customizeProtocol(AbstractProtocol<?> protocol) {
 		if (getAddress() != null) {
 			protocol.setAddress(getAddress());
@@ -275,6 +289,42 @@ public class TomcatReactiveWebServerFactory extends AbstractReactiveWebServerFac
 		return this.tomcatConnectorCustomizers;
 	}
 
+	/**
+	 * Set {@link TomcatProtocolHandlerCustomizer}s that should be applied to the Tomcat
+	 * {@link Connector}. Calling this method will replace any existing customizers.
+	 * @param tomcatProtocolHandlerCustomizers the customizers to set
+	 */
+	public void setTomcatProtocolHandlerCustomizers(
+			Collection<? extends TomcatProtocolHandlerCustomizer<?>> tomcatProtocolHandlerCustomizers) {
+		Assert.notNull(tomcatProtocolHandlerCustomizers,
+				"TomcatProtocolHandlerCustomizers must not be null");
+		this.tomcatProtocolHandlerCustomizers = new ArrayList<>(
+				tomcatProtocolHandlerCustomizers);
+	}
+
+	/**
+	 * Add {@link TomcatProtocolHandlerCustomizer}s that should be added to the Tomcat
+	 * {@link Connector}.
+	 * @param tomcatProtocolHandlerCustomizers the customizers to add
+	 */
+	@Override
+	public void addProtocolHandlerCustomizers(
+			TomcatProtocolHandlerCustomizer<?>... tomcatProtocolHandlerCustomizers) {
+		Assert.notNull(tomcatProtocolHandlerCustomizers,
+				"TomcatProtocolHandlerCustomizers must not be null");
+		this.tomcatProtocolHandlerCustomizers
+				.addAll(Arrays.asList(tomcatProtocolHandlerCustomizers));
+	}
+
+	/**
+	 * Returns a mutable collection of the {@link TomcatProtocolHandlerCustomizer}s that
+	 * will be applied to the Tomcat {@link Connector}.
+	 * @return the customizers that will be applied
+	 */
+	public Collection<TomcatProtocolHandlerCustomizer<?>> getTomcatProtocolHandlerCustomizers() {
+		return this.tomcatProtocolHandlerCustomizers;
+	}
+
 	@Override
 	public void addEngineValves(Valve... engineValves) {
 		Assert.notNull(engineValves, "Valves must not be null");

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/tomcat/TomcatServletWebServerFactory.java

@@ -58,9 +58,11 @@ import org.apache.catalina.webresources.AbstractResourceSet;
 import org.apache.catalina.webresources.EmptyResource;
 import org.apache.catalina.webresources.StandardRoot;
 import org.apache.coyote.AbstractProtocol;
+import org.apache.coyote.ProtocolHandler;
 import org.apache.coyote.http2.Http2Protocol;
 import org.apache.tomcat.util.scan.StandardJarScanFilter;
 
+import org.springframework.boot.util.LambdaSafe;
 import org.springframework.boot.web.server.ErrorPage;
 import org.springframework.boot.web.server.MimeMappings;
 import org.springframework.boot.web.server.WebServer;
@@ -117,6 +119,8 @@ public class TomcatServletWebServerFactory extends AbstractServletWebServerFacto
 
 	private List<TomcatConnectorCustomizer> tomcatConnectorCustomizers = new ArrayList<>();
 
+	private List<TomcatProtocolHandlerCustomizer<?>> tomcatProtocolHandlerCustomizers = new ArrayList<>();
+
 	private List<Connector> additionalTomcatConnectors = new ArrayList<>();
 
 	private ResourceLoader resourceLoader;
@@ -303,6 +307,7 @@ public class TomcatServletWebServerFactory extends AbstractServletWebServerFacto
 		if (connector.getProtocolHandler() instanceof AbstractProtocol) {
 			customizeProtocol((AbstractProtocol<?>) connector.getProtocolHandler());
 		}
+		invokeProtocolHandlerCustomizers(connector);
 		if (getUriEncoding() != null) {
 			connector.setURIEncoding(getUriEncoding().name());
 		}
@@ -325,6 +330,15 @@ public class TomcatServletWebServerFactory extends AbstractServletWebServerFacto
 		}
 	}
 
+	@SuppressWarnings("unchecked")
+	private void invokeProtocolHandlerCustomizers(Connector connector) {
+		ProtocolHandler protocolHandler = connector.getProtocolHandler();
+		LambdaSafe
+				.callbacks(TomcatProtocolHandlerCustomizer.class,
+						this.tomcatProtocolHandlerCustomizers, protocolHandler)
+				.invoke((customizer) -> customizer.customize(protocolHandler));
+	}
+
 	private void customizeSsl(Connector connector) {
 		new SslConnectorCustomizer(getSsl(), getSslStoreProvider()).customize(connector);
 		if (getHttp2() != null && getHttp2().isEnabled()) {
@@ -619,6 +633,42 @@ public class TomcatServletWebServerFactory extends AbstractServletWebServerFacto
 		return this.tomcatConnectorCustomizers;
 	}
 
+	/**
+	 * Set {@link TomcatProtocolHandlerCustomizer}s that should be applied to the Tomcat
+	 * {@link Connector}. Calling this method will replace any existing customizers.
+	 * @param tomcatProtocolHandlerCustomizer the customizers to set
+	 */
+	public void setTomcatProtocolHandlerCustomizers(
+			Collection<? extends TomcatProtocolHandlerCustomizer<?>> tomcatProtocolHandlerCustomizer) {
+		Assert.notNull(tomcatProtocolHandlerCustomizer,
+				"TomcatProtocolHandlerCustomizers must not be null");
+		this.tomcatProtocolHandlerCustomizers = new ArrayList<>(
+				tomcatProtocolHandlerCustomizer);
+	}
+
+	/**
+	 * Add {@link TomcatProtocolHandlerCustomizer}s that should be added to the Tomcat
+	 * {@link Connector}.
+	 * @param tomcatProtocolHandlerCustomizers the customizers to add
+	 */
+	@Override
+	public void addProtocolHandlerCustomizers(
+			TomcatProtocolHandlerCustomizer<?>... tomcatProtocolHandlerCustomizers) {
+		Assert.notNull(tomcatProtocolHandlerCustomizers,
+				"TomcatProtocolHandlerCustomizers must not be null");
+		this.tomcatProtocolHandlerCustomizers
+				.addAll(Arrays.asList(tomcatProtocolHandlerCustomizers));
+	}
+
+	/**
+	 * Returns a mutable collection of the {@link TomcatProtocolHandlerCustomizer}s that
+	 * will be applied to the Tomcat {@link Connector}.
+	 * @return the customizers that will be applied
+	 */
+	public Collection<TomcatProtocolHandlerCustomizer<?>> getTomcatProtocolHandlerCustomizers() {
+		return this.tomcatProtocolHandlerCustomizers;
+	}
+
 	/**
 	 * Add {@link Connector}s in addition to the default connector, e.g. for SSL or AJP
 	 * @param connectors the connectors to add

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/tomcat/TomcatReactiveWebServerFactoryTests.java

@@ -26,6 +26,8 @@ import org.apache.catalina.core.AprLifecycleListener;
 import org.apache.catalina.core.StandardContext;
 import org.apache.catalina.startup.Tomcat;
 import org.apache.catalina.valves.RemoteIpValve;
+import org.apache.coyote.ProtocolHandler;
+import org.apache.coyote.http11.AbstractHttp11Protocol;
 import org.junit.Test;
 import org.mockito.ArgumentCaptor;
 import org.mockito.InOrder;
@@ -121,6 +123,24 @@ public class TomcatReactiveWebServerFactoryTests
 				.withMessageContaining("Customizers must not be null");
 	}
 
+	@Test
+	public void setNullProtocolHandlerCustomizersShouldThrowException() {
+		TomcatReactiveWebServerFactory factory = getFactory();
+		assertThatIllegalArgumentException()
+				.isThrownBy(() -> factory.setTomcatProtocolHandlerCustomizers(null))
+				.withMessageContaining(
+						"TomcatProtocolHandlerCustomizers must not be null");
+	}
+
+	@Test
+	public void addNullProtocolHandlerCustomizersShouldThrowException() {
+		TomcatReactiveWebServerFactory factory = getFactory();
+		assertThatIllegalArgumentException().isThrownBy(() -> factory
+				.addProtocolHandlerCustomizers((TomcatProtocolHandlerCustomizer[]) null))
+				.withMessageContaining(
+						"TomcatProtocolHandlerCustomizers must not be null");
+	}
+
 	@Test
 	public void tomcatConnectorCustomizersShouldBeInvoked() {
 		TomcatReactiveWebServerFactory factory = getFactory();
@@ -136,6 +156,22 @@ public class TomcatReactiveWebServerFactoryTests
 		}
 	}
 
+	@Test
+	public void tomcatProtocolHandlerCustomizersShouldBeInvoked() {
+		TomcatReactiveWebServerFactory factory = getFactory();
+		HttpHandler handler = mock(HttpHandler.class);
+		TomcatProtocolHandlerCustomizer<AbstractHttp11Protocol>[] listeners = new TomcatProtocolHandlerCustomizer[4];
+		Arrays.setAll(listeners, (i) -> mock(TomcatProtocolHandlerCustomizer.class));
+		factory.setTomcatProtocolHandlerCustomizers(
+				Arrays.asList(listeners[0], listeners[1]));
+		factory.addProtocolHandlerCustomizers(listeners[2], listeners[3]);
+		this.webServer = factory.getWebServer(handler);
+		InOrder ordered = inOrder((Object[]) listeners);
+		for (TomcatProtocolHandlerCustomizer listener : listeners) {
+			ordered.verify(listener).customize(any(ProtocolHandler.class));
+		}
+	}
+
 	@Test
 	public void useForwardedHeaders() {
 		TomcatReactiveWebServerFactory factory = getFactory();

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/tomcat/TomcatServletWebServerFactoryTests.java

@@ -55,6 +55,8 @@ import org.apache.catalina.startup.Tomcat;
 import org.apache.catalina.util.CharsetMapper;
 import org.apache.catalina.valves.RemoteIpValve;
 import org.apache.catalina.webresources.TomcatURLStreamHandlerFactory;
+import org.apache.coyote.ProtocolHandler;
+import org.apache.coyote.http11.AbstractHttp11Protocol;
 import org.apache.jasper.servlet.JspServlet;
 import org.apache.tomcat.JarScanFilter;
 import org.apache.tomcat.JarScanType;
@@ -196,6 +198,35 @@ public class TomcatServletWebServerFactoryTests
 		}
 	}
 
+	@Test
+	public void tomcatProtocolHandlerCustomizersShouldBeInvoked() {
+		TomcatServletWebServerFactory factory = getFactory();
+		TomcatProtocolHandlerCustomizer<AbstractHttp11Protocol>[] listeners = new TomcatProtocolHandlerCustomizer[4];
+		Arrays.setAll(listeners, (i) -> mock(TomcatProtocolHandlerCustomizer.class));
+		factory.setTomcatProtocolHandlerCustomizers(
+				Arrays.asList(listeners[0], listeners[1]));
+		factory.addProtocolHandlerCustomizers(listeners[2], listeners[3]);
+		this.webServer = factory.getWebServer();
+		InOrder ordered = inOrder((Object[]) listeners);
+		for (TomcatProtocolHandlerCustomizer listener : listeners) {
+			ordered.verify(listener).customize(any(ProtocolHandler.class));
+		}
+	}
+
+	@Test
+	public void tomcatProtocolHandlerCanBeCustomized() {
+		TomcatServletWebServerFactory factory = getFactory();
+		TomcatProtocolHandlerCustomizer<AbstractHttp11Protocol> customizer = (
+				protocolHandler) -> protocolHandler.setProcessorCache(250);
+		factory.addProtocolHandlerCustomizers(customizer);
+		Tomcat tomcat = getTomcat(factory);
+		Connector connector = ((TomcatWebServer) this.webServer).getServiceConnectors()
+				.get(tomcat.getService())[0];
+		AbstractHttp11Protocol protocolHandler = (AbstractHttp11Protocol) connector
+				.getProtocolHandler();
+		assertThat(protocolHandler.getProcessorCache()).isEqualTo(250);
+	}
+
 	@Test
 	public void tomcatAdditionalConnectors() {
 		TomcatServletWebServerFactory factory = getFactory();
@@ -280,6 +311,24 @@ public class TomcatServletWebServerFactoryTests
 				.withMessageContaining("TomcatConnectorCustomizers must not be null");
 	}
 
+	@Test
+	public void setNullTomcatProtocolHandlerCustomizersThrows() {
+		TomcatServletWebServerFactory factory = getFactory();
+		assertThatIllegalArgumentException()
+				.isThrownBy(() -> factory.setTomcatProtocolHandlerCustomizers(null))
+				.withMessageContaining(
+						"TomcatProtocolHandlerCustomizers must not be null");
+	}
+
+	@Test
+	public void addNullTomcatProtocolHandlerCustomizersThrows() {
+		TomcatServletWebServerFactory factory = getFactory();
+		assertThatIllegalArgumentException().isThrownBy(() -> factory
+				.addProtocolHandlerCustomizers((TomcatProtocolHandlerCustomizer[]) null))
+				.withMessageContaining(
+						"TomcatProtocolHandlerCustomizers must not be null");
+	}
+
 	@Test
 	public void uriEncoding() {
 		TomcatServletWebServerFactory factory = getFactory();