Ensure only supported listeners are instantiated

Previously all EventListeners were eagerly instantiated
but that can cause problems because it happens quite early
in the lifecycle. Better to be explicit about the
supported types.

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

@@ -47,6 +47,7 @@ import org.springframework.core.io.ResourceLoader;
 import org.springframework.format.Formatter;
 import org.springframework.format.FormatterRegistry;
 import org.springframework.web.accept.ContentNegotiationManager;
+import org.springframework.web.context.request.RequestContextListener;
 import org.springframework.web.filter.HiddenHttpMethodFilter;
 import org.springframework.web.servlet.DispatcherServlet;
 import org.springframework.web.servlet.View;
@@ -134,6 +135,12 @@ public class WebMvcAutoConfiguration {
 			return resolver;
 		}
 
+		@Bean
+		@ConditionalOnMissingBean(RequestContextListener.class)
+		public RequestContextListener requestContextListener() {
+			return new RequestContextListener();
+		}
+
 		@Bean
 		@ConditionalOnBean(View.class)
 		public BeanNameViewResolver beanNameViewResolver() {

spring-boot/src/main/java/org/springframework/boot/context/embedded/EmbeddedWebApplicationContext.java

@@ -276,9 +276,11 @@ public class EmbeddedWebApplicationContext extends GenericWebApplicationContext
 			}
 		}
 
-		for (Entry<String, EventListener> listenerBean : getOrderedBeansOfType(EventListener.class)) {
+		Set<Class<?>> listenerTypes = ServletListenerRegistrationBean.getSupportedTypes();
+		for (Class<?> type : listenerTypes) {
+			for (Entry<String, ?> listenerBean : getOrderedBeansOfType(type)) {
 				String name = listenerBean.getKey();
-			EventListener listener = listenerBean.getValue();
+				EventListener listener = (EventListener) listenerBean.getValue();
 				if (ServletListenerRegistrationBean.isSupportedType(listener)
 						&& !filterRegistrations.contains(listener)) {
 					ServletListenerRegistrationBean<EventListener> registration = new ServletListenerRegistrationBean<EventListener>(
@@ -287,6 +289,7 @@ public class EmbeddedWebApplicationContext extends GenericWebApplicationContext
 					initializers.add(registration);
 				}
 			}
+		}
 
 		return initializers;
 	}

spring-boot/src/main/java/org/springframework/boot/context/embedded/ServletListenerRegistrationBean.java

@@ -118,4 +118,11 @@ public class ServletListenerRegistrationBean<T extends EventListener> extends
 		return false;
 	}
 
+	/**
+	 * @return the supportedTypes for this registration
+	 */
+	public static Set<Class<?>> getSupportedTypes() {
+		return SUPPORTED_TYPES;
+	}
+
 }

spring-boot/src/test/java/org/springframework/boot/context/embedded/EmbeddedWebApplicationContextTests.java

@@ -22,6 +22,7 @@ import java.util.Properties;
 import javax.servlet.Filter;
 import javax.servlet.Servlet;
 import javax.servlet.ServletContext;
+import javax.servlet.ServletContextListener;
 
 import org.junit.After;
 import org.junit.Before;
@@ -264,6 +265,18 @@ public class EmbeddedWebApplicationContextTests {
 		ordered.verify(initializer2).onStartup(servletContext);
 	}
 
+	@Test
+	public void servletContextListenerBeans() throws Exception {
+		addEmbeddedServletContainerFactoryBean();
+		ServletContextListener initializer = mock(ServletContextListener.class);
+		this.context.registerBeanDefinition("initializerBean",
+				beanDefinition(initializer));
+		this.context.refresh();
+		ServletContext servletContext = getEmbeddedServletContainerFactory()
+				.getServletContext();
+		verify(servletContext).addListener(initializer);
+	}
+
 	@Test
 	public void unorderedServletContextInitializerBeans() throws Exception {
 		addEmbeddedServletContainerFactoryBean();