Register classes that implement multiple Servlet interfaces

Closes gh-39056

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

@@ -21,6 +21,7 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.EventListener;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
@@ -67,7 +68,7 @@ public class ServletContextInitializerBeans extends AbstractCollection<ServletCo
 	/**
 	 * Seen bean instances or bean names.
 	 */
-	private final Set<Object> seen = new HashSet<>();
+	private final Seen seen = new Seen();
 
 	private final MultiValueMap<Class<?>, ServletContextInitializer> initializers;
 
@@ -129,7 +130,7 @@ public class ServletContextInitializerBeans extends AbstractCollection<ServletCo
 		this.initializers.add(type, initializer);
 		if (source != null) {
 			// Mark the underlying source as seen in case it wraps an existing bean
-			this.seen.add(source);
+			this.seen.add(type, source);
 		}
 		if (logger.isTraceEnabled()) {
 			String resourceDescription = getResourceDescription(beanName, beanFactory);
@@ -174,7 +175,7 @@ public class ServletContextInitializerBeans extends AbstractCollection<ServletCo
 		for (Entry<String, B> entry : entries) {
 			String beanName = entry.getKey();
 			B bean = entry.getValue();
-			if (this.seen.add(bean)) {
+			if (this.seen.add(type, bean)) {
 				// One that we haven't already seen
 				RegistrationBean registration = adapter.createRegistrationBean(beanName, bean, entries.size());
 				int order = getOrder(bean);
@@ -198,17 +199,17 @@ public class ServletContextInitializerBeans extends AbstractCollection<ServletCo
 	}
 
 	private <T> List<Entry<String, T>> getOrderedBeansOfType(ListableBeanFactory beanFactory, Class<T> type) {
-		return getOrderedBeansOfType(beanFactory, type, Collections.emptySet());
+		return getOrderedBeansOfType(beanFactory, type, Seen.empty());
 	}
 
 	private <T> List<Entry<String, T>> getOrderedBeansOfType(ListableBeanFactory beanFactory, Class<T> type,
-			Set<?> excludes) {
+			Seen seen) {
 		String[] names = beanFactory.getBeanNamesForType(type, true, false);
 		Map<String, T> map = new LinkedHashMap<>();
 		for (String name : names) {
-			if (!excludes.contains(name) && !ScopedProxyUtils.isScopedTarget(name)) {
+			if (!seen.contains(type, name) && !ScopedProxyUtils.isScopedTarget(name)) {
 				T bean = beanFactory.getBean(name, type);
-				if (!excludes.contains(bean)) {
+				if (!seen.contains(type, bean)) {
 					map.put(name, bean);
 				}
 			}
@@ -310,4 +311,37 @@ public class ServletContextInitializerBeans extends AbstractCollection<ServletCo
 
 	}
 
+	private static final class Seen {
+
+		private final Map<Class<?>, Set<Object>> seen = new HashMap<>();
+
+		boolean add(Class<?> type, Object object) {
+			if (contains(type, object)) {
+				return false;
+			}
+			return this.seen.computeIfAbsent(type, (ignore) -> new HashSet<>()).add(object);
+		}
+
+		boolean contains(Class<?> type, Object object) {
+			if (this.seen.isEmpty()) {
+				return false;
+			}
+			// If it has been directly seen, or the implemented ServletContextInitializer
+			// has been seen already
+			if (type != ServletContextInitializer.class
+					&& this.seen.getOrDefault(type, Collections.emptySet()).contains(object)) {
+				return true;
+			}
+			if (this.seen.getOrDefault(ServletContextInitializer.class, Collections.emptySet()).contains(object)) {
+				return true;
+			}
+			return false;
+		}
+
+		static Seen empty() {
+			return new Seen();
+		}
+
+	}
+
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 the original author or authors.
+ * Copyright 2012-2024 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.
@@ -38,6 +38,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  * Tests for {@link ServletContextInitializerBeans}.
  *
  * @author Andy Wilkinson
+ * @author Moritz Halbritter
  */
 class ServletContextInitializerBeansTests {
 
@@ -82,6 +83,26 @@ class ServletContextInitializerBeansTests {
 			.isInstanceOf(HttpSessionIdListener.class);
 	}
 
+	@Test
+	void classesThatImplementMultipleInterfacesAreRegisteredForAllOfThem() {
+		load(MultipleInterfacesConfiguration.class);
+		ServletContextInitializerBeans initializerBeans = new ServletContextInitializerBeans(
+				this.context.getBeanFactory());
+		assertThat(initializerBeans).hasSize(3);
+		assertThat(initializerBeans).element(0)
+			.isInstanceOf(ServletRegistrationBean.class)
+			.extracting((initializer) -> ((ServletRegistrationBean<?>) initializer).getServlet())
+			.isInstanceOf(TestServletAndFilterAndListener.class);
+		assertThat(initializerBeans).element(1)
+			.isInstanceOf(FilterRegistrationBean.class)
+			.extracting((initializer) -> ((FilterRegistrationBean<?>) initializer).getFilter())
+			.isInstanceOf(TestServletAndFilterAndListener.class);
+		assertThat(initializerBeans).element(2)
+			.isInstanceOf(ServletListenerRegistrationBean.class)
+			.extracting((initializer) -> ((ServletListenerRegistrationBean<?>) initializer).getListener())
+			.isInstanceOf(TestServletAndFilterAndListener.class);
+	}
+
 	private void load(Class<?>... configuration) {
 		this.context = new AnnotationConfigApplicationContext(configuration);
 	}
@@ -106,6 +127,16 @@ class ServletContextInitializerBeansTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class MultipleInterfacesConfiguration {
+
+		@Bean
+		TestServletAndFilterAndListener testServletAndFilterAndListener() {
+			return new TestServletAndFilterAndListener();
+		}
+
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	static class TestConfiguration {
 

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

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2012-2024 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.servlet;
+
+import java.io.IOException;
+
+import jakarta.servlet.Filter;
+import jakarta.servlet.FilterChain;
+import jakarta.servlet.Servlet;
+import jakarta.servlet.ServletConfig;
+import jakarta.servlet.ServletException;
+import jakarta.servlet.ServletRequest;
+import jakarta.servlet.ServletRequestListener;
+import jakarta.servlet.ServletResponse;
+
+class TestServletAndFilterAndListener implements Servlet, Filter, ServletRequestListener {
+
+	@Override
+	public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
+			throws IOException, ServletException {
+
+	}
+
+	@Override
+	public void init(ServletConfig servletConfig) throws ServletException {
+
+	}
+
+	@Override
+	public ServletConfig getServletConfig() {
+		return null;
+	}
+
+	@Override
+	public void service(ServletRequest servletRequest, ServletResponse servletResponse)
+			throws ServletException, IOException {
+
+	}
+
+	@Override
+	public String getServletInfo() {
+		return null;
+	}
+
+	@Override
+	public void destroy() {
+
+	}
+
+}