Do not assume HTTP protocol when customizing processor cache

Closes gh-16413

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

@@ -133,9 +133,12 @@ public class TomcatWebServerFactoryCustomizer implements
 
 	private void customizeProcessorCache(ConfigurableTomcatWebServerFactory factory,
 			int processorCache) {
-		factory.addConnectorCustomizers((
-				connector) -> ((AbstractHttp11Protocol<?>) connector.getProtocolHandler())
-						.setProcessorCache(processorCache));
+		factory.addConnectorCustomizers((connector) -> {
+			ProtocolHandler handler = connector.getProtocolHandler();
+			if (handler instanceof AbstractProtocol) {
+				((AbstractProtocol<?>) handler).setProcessorCache(processorCache);
+			}
+		});
 	}
 
 	private void customizeMaxConnections(ConfigurableTomcatWebServerFactory factory,

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/embedded/TomcatWebServerFactoryCustomizerTests.java

@@ -36,6 +36,7 @@ import org.springframework.boot.context.properties.bind.Binder;
 import org.springframework.boot.context.properties.source.ConfigurationPropertySources;
 import org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory;
 import org.springframework.boot.web.embedded.tomcat.TomcatWebServer;
+import org.springframework.boot.web.server.WebServer;
 import org.springframework.mock.env.MockEnvironment;
 import org.springframework.test.context.support.TestPropertySourceUtils;
 import org.springframework.util.unit.DataSize;
@@ -421,6 +422,16 @@ public class TomcatWebServerFactoryCustomizerTests {
 				.getIpv6Canonical()).isTrue();
 	}
 
+	@Test
+	public void ajpConnectorCanBeCustomized() {
+		TomcatServletWebServerFactory factory = new TomcatServletWebServerFactory(0);
+		factory.setProtocol("AJP/1.3");
+		this.customizer.customize(factory);
+		WebServer server = factory.getWebServer();
+		server.start();
+		server.stop();
+	}
+
 	private void bind(String... inlinedProperties) {
 		TestPropertySourceUtils.addInlinedPropertiesToEnvironment(this.environment,
 				inlinedProperties);