Support Jetty 9.4 and upgrade to 9.4.0.v20161208

Update `JettyEmbeddedServletContainerFactory` to support Jetty 9.4
directly and Jetty 9.3 via reflection. The primary difference between
Jetty 9.3 and 9.4 are the session management classes. Websocket suppport
has also been updates, but this is handled transparently by the
Spring Framework support.

Fixes gh-7599

spring-boot-samples/spring-boot-sample-jetty93/src/main/java/sample/jetty93/ExampleServletContextListener.java

@@ -0,0 +1,40 @@
+/*
+ * 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.jetty93;
+
+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-samples/spring-boot-sample-jetty93/src/main/java/sample/jetty93/SampleJetty93Application.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2012-2013 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.jetty93;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class SampleJetty93Application {
+
+	public static void main(String[] args) throws Exception {
+		SpringApplication.run(SampleJetty93Application.class, args);
+	}
+
+}

spring-boot-samples/spring-boot-sample-jetty93/src/main/java/sample/jetty93/service/HelloWorldService.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2012-2013 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.jetty93.service;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Component;
+
+@Component
+public class HelloWorldService {
+
+	@Value("${name:World}")
+	private String name;
+
+	public String getHelloMessage() {
+		return "Hello " + this.name;
+	}
+
+}

spring-boot-samples/spring-boot-sample-jetty93/src/main/java/sample/jetty93/web/SampleController.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2012-2016 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.jetty93.web;
+
+import java.util.Date;
+
+import javax.servlet.http.HttpServletRequest;
+
+import sample.jetty93.service.HelloWorldService;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Controller;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.ResponseBody;
+
+@Controller
+public class SampleController {
+
+	@Autowired
+	private HelloWorldService helloWorldService;
+
+	@GetMapping("/")
+	@ResponseBody
+	public String helloWorld(HttpServletRequest request) {
+		request.getSession(true).setAttribute("date", new Date());
+		return this.helloWorldService.getHelloMessage();
+	}
+
+}