Support ServletContextListener with Jetty 9

Call `context.getServletContext().setExtendedListenerTypes(true)` to
ensure that ServletContextListeners can be registered with Jetty 9.

Fixes gh-2058

spring-boot-samples/spring-boot-sample-jetty/src/main/java/sample/jetty/ExampleServletContextListener.java

+/*
+ * Copyright 2012-2014 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
+ *
+ *      http://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 sample.jetty;
+
+import javax.servlet.ServletContextEvent;
+import javax.servlet.ServletContextListener;
+
+import org.springframework.stereotype.Component;
+
+/**
+ * Simple {@link ServletContextListener} to test gh-2058.
+ */
+@Component
+public class ExampleServletContextListener implements ServletContextListener {
+
+	@Override
+	public void contextInitialized(ServletContextEvent sce) {
+		System.out.println("*** contextInitialized");
+	}
+
+	@Override
+	public void contextDestroyed(ServletContextEvent sce) {
+		System.out.println("*** contextDestroyed");
+	}
+
+}

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

@@ -118,7 +118,6 @@ public class JettyEmbeddedServletContainerFactory extends
 		configureWebAppContext(context, initializers);
 		server.setHandler(context);
 		this.logger.info("Server initialized with port: " + port);
-
 		if (getSsl() != null) {
 			SslContextFactory sslContextFactory = new SslContextFactory();
 			configureSsl(sslContextFactory, getSsl());
@@ -126,11 +125,9 @@ public class JettyEmbeddedServletContainerFactory extends
 					server, sslContextFactory, port);
 			server.setConnectors(new Connector[] { connector });
 		}
-
 		for (JettyServerCustomizer customizer : getServerCustomizers()) {
 			customizer.customize(server);
 		}
-
 		return getJettyEmbeddedServletContainer(server);
 	}
 
@@ -224,6 +221,7 @@ public class JettyEmbeddedServletContainerFactory extends
 	protected final void configureWebAppContext(WebAppContext context,
 			ServletContextInitializer... initializers) {
 		Assert.notNull(context, "Context must not be null");
+		setExtendedListenerTypes(context);
 		if (this.resourceLoader != null) {
 			context.setClassLoader(this.resourceLoader.getClassLoader());
 		}
@@ -248,6 +246,15 @@ public class JettyEmbeddedServletContainerFactory extends
 		postProcessWebAppContext(context);
 	}
 
+	private void setExtendedListenerTypes(WebAppContext context) {
+		try {
+			context.getServletContext().setExtendedListenerTypes(true);
+		}
+		catch (NoSuchMethodError ex) {
+			// Not available on Jetty 8
+		}
+	}
+
 	private void configureDocumentRoot(WebAppContext handler) {
 		File root = getValidDocumentRoot();
 		if (root != null) {