fixes so the sample app runs

spring-cloud-function-adapters/spring-cloud-function-serverless-web/README.md

@@ -8,6 +8,12 @@ A sample is provided in [sample](https://github.com/spring-cloud/spring-cloud-fu
 
 _NOTE: Although this module is AWS specific, this dependency is protocol only (not binary), therefore there is no AWS dependnecies._
 
+_NOTE: The serverless `ServletWebServerFactory` is declared with `@ConditionalOnMissingBean`. If your
+application defines its own `ServletWebServerFactory` bean (for example Tomcat/Jetty/Undertow customization),
+that custom bean will take precedence and can disable the serverless adapter path. For serverless-web usage,
+do not provide a competing `ServletWebServerFactory` bean unless it delegates to
+`ServerlessAutoConfiguration.ServerlessServletWebServerFactory`._
+
 The aformentioned proxy is identified as AWS Lambda [handler](https://github.com/spring-cloud/spring-cloud-function/blob/serverless-web/spring-cloud-function-adapters/spring-cloud-function-adapter-aws-web/sample/pet-store/template.yml#L14)
 
 The main Spring Boot configuration file is identified as [MAIN_CLASS](https://github.com/spring-cloud/spring-cloud-function/blob/serverless-web/spring-cloud-function-adapters/spring-cloud-function-adapter-aws-web/sample/pet-store/template.yml#L22)

spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/FunctionClassUtils.java

@@ -42,7 +42,7 @@
  */
 public final class FunctionClassUtils {
 
-	private static Log logger = LogFactory.getLog(FunctionClassUtils.class);
+	private static final Log LOGGER = LogFactory.getLog(FunctionClassUtils.class);
 
 	private static Class<?> MAIN_CLASS;
 
@@ -91,20 +91,20 @@ else if (System.getProperty("MAIN_CLASS") != null) {
 						+ "entry in META-INF/MANIFEST.MF (in that order).", ex);
 			}
 		}
-		logger.info("Main class: " + mainClass);
+		LOGGER.info("Main class: " + mainClass);
 		return mainClass;
 	}
 
 	private static Class<?> getStartClass(List<URL> list, ClassLoader classLoader) {
-		if (logger.isTraceEnabled()) {
-			logger.trace("Searching manifests: " + list);
+		if (LOGGER.isTraceEnabled()) {
+			LOGGER.trace("Searching manifests: " + list);
 		}
 		for (URL url : list) {
 			try {
 				InputStream inputStream = null;
 				Manifest manifest = new Manifest(url.openStream());
-				logger.info("Searching for start class in manifest: " + url);
-				if (logger.isDebugEnabled()) {
+				LOGGER.info("Searching for start class in manifest: " + url);
+				if (LOGGER.isDebugEnabled()) {
 					manifest.write(System.out);
 				}
 				try {
@@ -135,7 +135,7 @@ private static Class<?> getStartClass(List<URL> list, ClassLoader classLoader) {
 				}
 			}
 			catch (Exception ex) {
-				logger.debug("Failed to determine Start-Class in manifest file of " + url, ex);
+				LOGGER.debug("Failed to determine Start-Class in manifest file of " + url, ex);
 			}
 		}
 		return null;

spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ServerlessAsyncContext.java

@@ -30,9 +30,9 @@
 import jakarta.servlet.ServletResponse;
 import jakarta.servlet.http.HttpServletRequest;
 import jakarta.servlet.http.HttpServletResponse;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.beans.BeanUtils;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.util.WebUtils;
 

spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ServerlessAutoConfiguration.java

@@ -21,6 +21,7 @@
 
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.InitializingBean;
+import org.springframework.boot.autoconfigure.AutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.web.server.WebServer;
 import org.springframework.boot.web.server.WebServerException;
@@ -39,13 +40,20 @@
  * @author Oleg Zhurakousky
  * @since 4.x
  */
+@AutoConfiguration(beforeName = {
+	"org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration",
+	"org.springframework.boot.tomcat.autoconfigure.servlet.TomcatServletWebServerAutoConfiguration",
+	"org.springframework.boot.jetty.autoconfigure.servlet.JettyServletWebServerAutoConfiguration",
+	"org.springframework.boot.undertow.autoconfigure.servlet.UndertowServletWebServerAutoConfiguration"
+})
 @Configuration(proxyBeanMethods = false)
 public class ServerlessAutoConfiguration {
-	private static Log logger = LogFactory.getLog(ServerlessAutoConfiguration.class);
+	private static final Log LOGGER = LogFactory.getLog(ServerlessAutoConfiguration.class);
 
 	@Bean
 	@ConditionalOnMissingBean
 	public ServletWebServerFactory servletWebServerFactory() {
+		// A user-defined ServletWebServerFactory bean will override this and may bypass serverless initialization.
 		return new ServerlessServletWebServerFactory();
 	}
 
@@ -82,14 +90,14 @@ public void setApplicationContext(ApplicationContext applicationContext) throws
 		@Override
 		public void afterPropertiesSet() throws Exception {
 			if (applicationContext instanceof ServletWebServerApplicationContext servletApplicationContext) {
-				logger.info("Configuring Serverless Web Container");
+				LOGGER.info("Configuring Serverless Web Container");
 				ServerlessServletContext servletContext = new ServerlessServletContext();
 				servletApplicationContext.setServletContext(servletContext);
 				DispatcherServlet dispatcher = applicationContext.getBean(DispatcherServlet.class);
 				try {
-					logger.info("Initializing DispatcherServlet");
+					LOGGER.info("Initializing DispatcherServlet");
 					dispatcher.init(new ProxyServletConfig(servletApplicationContext.getServletContext()));
-					logger.info("Initialized DispatcherServlet");
+					LOGGER.info("Initialized DispatcherServlet");
 				}
 				catch (Exception e) {
 					throw new IllegalStateException("Failed to create Spring MVC DispatcherServlet proxy", e);
@@ -99,7 +107,7 @@ public void afterPropertiesSet() throws Exception {
 				}
 			}
 			else {
-				logger.debug("Skipping Serverless configuration for " + this.applicationContext);
+				LOGGER.debug("Skipping Serverless configuration for " + this.applicationContext);
 			}
 		}
 	}

spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ServerlessHttpServletRequest.java

@@ -58,9 +58,9 @@
 import jakarta.servlet.http.HttpSession;
 import jakarta.servlet.http.HttpUpgradeHandler;
 import jakarta.servlet.http.Part;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.http.HttpHeaders;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.LinkedMultiValueMap;
@@ -559,9 +559,7 @@ public void clearAttributes() {
 	 * <strong>not</strong> take into consideration any locales specified via the
 	 * {@code Accept-Language} header.
 	 *
-	 * @see javax.servlet.ServletRequest#getLocale()
-	 * @see #addPreferredLocale(Locale)
-	 * @see #setPreferredLocales(List)
+	 * @see jakarta.servlet.ServletRequest#getLocale()
 	 */
 	@Override
 	public Locale getLocale() {
@@ -580,20 +578,17 @@ public Locale getLocale() {
 	 * <strong>not</strong> take into consideration any locales specified via the
 	 * {@code Accept-Language} header.
 	 *
-	 * @see javax.servlet.ServletRequest#getLocales()
-	 * @see #addPreferredLocale(Locale)
-	 * @see #setPreferredLocales(List)
+	 * @see jakarta.servlet.ServletRequest#getLocales()
 	 */
 	@Override
 	public Enumeration<Locale> getLocales() {
 		return Collections.enumeration(this.locales);
 	}
 
 	/**
-	 * Return {@code true} if the {@link #setSecure secure} flag has been set to
-	 * {@code true} or if the {@link #getScheme scheme} is {@code https}.
+	 * Return {@code true} if the {@link #getScheme scheme} is {@code https}.
 	 *
-	 * @see javax.servlet.ServletRequest#isSecure()
+	 * @see jakarta.servlet.ServletRequest#isSecure()
 	 */
 	@Override
 	public boolean isSecure() {

spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ServerlessHttpServletResponse.java

@@ -38,9 +38,9 @@
 import jakarta.servlet.WriteListener;
 import jakarta.servlet.http.Cookie;
 import jakarta.servlet.http.HttpServletResponse;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.http.HttpHeaders;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.util.WebUtils;
 
@@ -118,8 +118,7 @@ public byte[] getContentAsByteArray() {
 	 * specified for the response by the application, either through
 	 * {@link HttpServletResponse} methods or through a charset parameter on the
 	 * {@code Content-Type}. If no charset has been explicitly defined, the
-	 * {@linkplain #setDefaultCharacterEncoding(String) default character encoding}
-	 * will be used.
+	 * default character encoding will be used.
 	 *
 	 * @return the content as a {@code String}
 	 * @throws UnsupportedEncodingException if the character encoding is not

spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ServerlessMVC.java

@@ -23,6 +23,7 @@
 import java.util.Enumeration;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Map;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 import java.util.stream.Stream;
@@ -33,6 +34,7 @@
 import jakarta.servlet.Filter;
 import jakarta.servlet.FilterChain;
 import jakarta.servlet.FilterConfig;
+import jakarta.servlet.FilterRegistration;
 import jakarta.servlet.RequestDispatcher;
 import jakarta.servlet.Servlet;
 import jakarta.servlet.ServletConfig;
@@ -44,12 +46,12 @@
 import jakarta.servlet.http.HttpServletResponse;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.web.server.servlet.context.ServletWebServerApplicationContext;
 import org.springframework.boot.webmvc.autoconfigure.DispatcherServletAutoConfiguration;
 import org.springframework.http.HttpStatus;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
@@ -72,12 +74,15 @@ public final class ServerlessMVC {
 	 */
 	public static String INIT_TIMEOUT = "contextInitTimeout";
 
-	private static Log LOG = LogFactory.getLog(ServerlessMVC.class);
+	private static final Log LOGGER = LogFactory.getLog(ServerlessMVC.class);
 
 	private volatile DispatcherServlet dispatcher;
 
 	private volatile ServletWebServerApplicationContext applicationContext;
 
+	@Nullable
+	private volatile Throwable startupFailure;
+
 	private final CountDownLatch contextStartupLatch = new CountDownLatch(1);
 
 	private final long initializationTimeout;
@@ -107,16 +112,18 @@ private ServerlessMVC() {
 	private void initializeContextAsync(Class<?>... componentClasses) {
 		new Thread(() -> {
 			try {
-				LOG.info("Starting application with the following configuration classes:");
-				Stream.of(componentClasses).forEach(clazz -> LOG.info(clazz.getSimpleName()));
+				LOGGER.info("Starting application with the following configuration classes:");
+				Stream.of(componentClasses).forEach(clazz -> LOGGER.info(clazz.getSimpleName()));
 				initContext(componentClasses);
 			}
 			catch (Exception e) {
-				throw new IllegalStateException(e);
+				this.startupFailure = e;
+				LOGGER.error("Application failed to initialize.", e);
 			}
 			finally {
 				contextStartupLatch.countDown();
-				LOG.info("Application is started successfully.");
+				LOGGER.info((this.startupFailure == null) ? "Application is started successfully."
+						: "Application startup finished with errors.");
 			}
 		}).start();
 	}
@@ -126,41 +133,39 @@ private void initContext(Class<?>... componentClasses) {
 		if (this.applicationContext.containsBean(DispatcherServletAutoConfiguration.DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)) {
 			this.dispatcher = this.applicationContext.getBean(DispatcherServlet.class);
 		}
+		Assert.state(this.dispatcher != null, "DispatcherServlet bean was not initialized. "
+				+ "Ensure ServerlessAutoConfiguration is active and selected as the ServletWebServerFactory.");
 	}
 
 	public ConfigurableWebApplicationContext getApplicationContext() {
-		this.waitForContext();
+		this.assertContextReady();
 		return this.applicationContext;
 	}
 
 	public ServletContext getServletContext() {
-		this.waitForContext();
+		this.assertContextReady();
 		return this.dispatcher.getServletContext();
 	}
 
 	public void stop() {
-		this.waitForContext();
+		this.assertContextReady();
 		this.applicationContext.stop();
 	}
 
 	/**
-	 * Perform a request and return a type that allows chaining further actions,
-	 * such as asserting expectations, on the result.
+	 * Process a serverless request through the configured servlet/filter chain.
 	 *
-	 * @param requestBuilder used to prepare the request to execute; see static
-	 *                       factory methods in
-	 *                       {@link org.springframework.test.web.servlet.request.MockMvcRequestBuilders}
-	 * @return an instance of {@link ResultActions} (never {@code null})
-	 * @see org.springframework.test.web.servlet.request.MockMvcRequestBuilders
-	 * @see org.springframework.test.web.servlet.result.MockMvcResultMatchers
+	 * @param request the incoming request
+	 * @param response the outgoing response
 	 */
 	public void service(HttpServletRequest request, HttpServletResponse response) throws Exception {
-		Assert.state(this.waitForContext(), "Failed to initialize Application within the specified time of " + this.initializationTimeout + " milliseconds. "
-				+ "If you need to increase it, please set " + INIT_TIMEOUT + " environment variable");
+		this.assertContextReady();
 		this.service(request, response, (CountDownLatch) null);
 	}
 
 	public void service(HttpServletRequest request, HttpServletResponse response, CountDownLatch latch) throws Exception {
+		Assert.state(this.dispatcher != null, "DispatcherServlet is not initialized. "
+				+ "Ensure ServerlessAutoConfiguration is active and selected as the ServletWebServerFactory.");
 		ProxyFilterChain filterChain = new ProxyFilterChain(this.dispatcher);
 		filterChain.doFilter(request, response);
 
@@ -195,6 +200,18 @@ public boolean waitForContext() {
 		return false;
 	}
 
+	private void assertContextReady() {
+		Assert.state(this.waitForContext(), "Failed to initialize Application within the specified time of " + this.initializationTimeout + " milliseconds. "
+				+ "If you need to increase it, please set " + INIT_TIMEOUT + " environment variable");
+		if (this.startupFailure != null) {
+			throw new IllegalStateException("Application context failed to initialize. "
+					+ "Ensure ServerlessAutoConfiguration is active and selected as the ServletWebServerFactory.", this.startupFailure);
+		}
+		Assert.state(this.dispatcher != null, "DispatcherServlet is not initialized. "
+				+ "Ensure ServerlessAutoConfiguration is active and selected as the ServletWebServerFactory.");
+		Assert.state(this.applicationContext != null, "ApplicationContext is not initialized.");
+	}
+
 	private static class ProxyFilterChain implements FilterChain {
 
 		@Nullable
@@ -217,7 +234,17 @@ private static class ProxyFilterChain implements FilterChain {
 		 */
 		ProxyFilterChain(DispatcherServlet servlet) {
 			List<Filter> filters = new ArrayList<>();
-			servlet.getServletContext().getFilterRegistrations().values().forEach(fr -> filters.add(((ServerlessFilterRegistration) fr).getFilter()));
+			for (Map.Entry<String, ? extends FilterRegistration> entry : servlet.getServletContext().getFilterRegistrations()
+					.entrySet()) {
+				FilterRegistration registration = entry.getValue();
+				if (registration instanceof ServerlessFilterRegistration serverlessFilterRegistration) {
+					filters.add(serverlessFilterRegistration.getFilter());
+				}
+				else {
+					LOGGER.debug("Skipping unsupported filter registration type '" + registration.getClass().getName()
+							+ "' for filter '" + entry.getKey() + "'");
+				}
+			}
 			Assert.notNull(filters, "filters cannot be null");
 			Assert.noNullElements(filters, "filters cannot contain null values");
 			this.filters = initFilterList(servlet, filters.toArray(new Filter[] {}));
@@ -309,7 +336,7 @@ public void doFilter(ServletRequest request, ServletResponse response, FilterCha
 						((ServerlessHttpServletRequest) request).setRequestURI("/error");
 					}
 
-					LOG.error("Failed processing the request to: " + ((HttpServletRequest) request).getRequestURI(), e);
+					LOGGER.error("Failed processing the request to: " + ((HttpServletRequest) request).getRequestURI(), e);
 
 					this.delegateServlet.service(request, response);
 				}

spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ServerlessServletContext.java

@@ -58,7 +58,7 @@
  */
 public class ServerlessServletContext implements ServletContext {
 
-	private Log logger = LogFactory.getLog(ServerlessServletContext.class);
+	private static final Log LOGGER = LogFactory.getLog(ServerlessServletContext.class);
 
 	private HashMap<String, Object> attributes = new HashMap<>();
 
@@ -145,12 +145,12 @@ public RequestDispatcher getNamedDispatcher(String name) {
 
 	@Override
 	public void log(String msg) {
-		this.logger.info(msg);
+		this.LOGGER.info(msg);
 	}
 
 	@Override
 	public void log(String message, Throwable throwable) {
-		this.logger.error(message, throwable);
+		this.LOGGER.error(message, throwable);
 	}
 
 	@Override