Update websocket support for Jetty 9.3+

Due to a few changes in `WebSocketServerFactory` and `Session` API, our
`JettyRequestUpgradeStrategy` and `JettyWebSocketSession` needed to
adapt. As of 9.3.15+ and 9.4.0+, some reflection is required to support
previous versions.

Spring 4.3 websocket officially supports Jetty 9.1 to 9.3.

Issue: SPR-14940

Author: bclozel

build.gradle

@@ -56,6 +56,7 @@ configure(allprojects) { project ->
 	ext.jasperreportsVersion = "6.2.1"  // our tests fail with JR-internal NPEs against 6.2.2 and higher
 	ext.javamailVersion      = "1.5.6"
 	ext.jettyVersion         = "9.3.13.v20161014"
+	ext.jetty94Version       = "9.4.0.v20161208" // for spring-websocket support
 	ext.jodaVersion          = "2.9.6"
 	ext.jrubyVersion         = "1.7.26"  // JRuby 9000 only supported through JSR-223 (StandardScriptFactory)
 	ext.jtaVersion           = "1.2"
@@ -949,11 +950,11 @@ project("spring-websocket") {
 		optional("org.eclipse.jetty:jetty-webapp:${jettyVersion}") {
 			exclude group: "javax.servlet", module: "javax.servlet"
 		}
-		optional("org.eclipse.jetty.websocket:websocket-server:${jettyVersion}") {
+		optional("org.eclipse.jetty.websocket:websocket-server:${jetty94Version}") {
 			exclude group: "javax.servlet", module: "javax.servlet"
 		}
-		optional("org.eclipse.jetty.websocket:websocket-client:${jettyVersion}")
-		optional("org.eclipse.jetty:jetty-client:${jettyVersion}")
+		optional("org.eclipse.jetty.websocket:websocket-client:${jetty94Version}")
+		optional("org.eclipse.jetty:jetty-client:${jetty94Version}")
 		optional("io.undertow:undertow-core:${undertowVersion}")
 		optional("io.undertow:undertow-servlet:${undertowVersion}") {
 			exclude group: "org.jboss.spec.javax.servlet", module: "jboss-servlet-api_3.1_spec"

spring-websocket/src/main/java/org/springframework/web/socket/adapter/jetty/JettyWebSocketSession.java

@@ -17,6 +17,7 @@
 package org.springframework.web.socket.adapter.jetty;
 
 import java.io.IOException;
+import java.lang.reflect.Method;
 import java.net.InetSocketAddress;
 import java.net.URI;
 import java.security.Principal;
@@ -26,11 +27,14 @@
 
 import org.eclipse.jetty.websocket.api.RemoteEndpoint;
 import org.eclipse.jetty.websocket.api.Session;
+import org.eclipse.jetty.websocket.api.UpgradeRequest;
+import org.eclipse.jetty.websocket.api.UpgradeResponse;
 import org.eclipse.jetty.websocket.api.WebSocketException;
 import org.eclipse.jetty.websocket.api.extensions.ExtensionConfig;
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.util.ObjectUtils;
+import org.springframework.util.ReflectionUtils;
 import org.springframework.web.socket.BinaryMessage;
 import org.springframework.web.socket.CloseStatus;
 import org.springframework.web.socket.PingMessage;
@@ -45,10 +49,22 @@
  *
  * @author Phillip Webb
  * @author Rossen Stoyanchev
+ * @author Brian Clozel
  * @since 4.0
  */
 public class JettyWebSocketSession extends AbstractWebSocketSession<Session> {
 
+	// As of Jetty 9.4, UpgradeRequest and UpgradeResponse are interfaces instead of classes
+	private static final boolean isJetty94;
+
+	private static Method getUpgradeRequest;
+	private static Method getUpgradeResponse;
+	private static Method getRequestURI;
+	private static Method getHeaders;
+	private static Method getAcceptedSubProtocol;
+	private static Method getExtensions;
+	private static Method getUserPrincipal;
+
 	private String id;
 
 	private URI uri;
@@ -61,6 +77,23 @@ public class JettyWebSocketSession extends AbstractWebSocketSession<Session> {
 
 	private Principal user;
 
+	static {
+		isJetty94 = UpgradeRequest.class.isInterface();
+		if (!isJetty94) {
+			try {
+				getUpgradeRequest = Session.class.getMethod("getUpgradeRequest");
+				getUpgradeResponse = Session.class.getMethod("getUpgradeResponse");
+				getRequestURI = UpgradeRequest.class.getMethod("getRequestURI");
+				getHeaders = UpgradeRequest.class.getMethod("getHeaders");
+				getAcceptedSubProtocol = UpgradeResponse.class.getMethod("getAcceptedSubProtocol");
+				getExtensions = UpgradeResponse.class.getMethod("getExtensions");
+				getUserPrincipal = UpgradeRequest.class.getMethod("getUserPrincipal");
+			}
+			catch (NoSuchMethodException ex) {
+				throw new IllegalStateException("Incompatible Jetty API", ex);
+			}
+		}
+	}
 
 	/**
 	 * Create a new {@link JettyWebSocketSession} instance.
@@ -164,20 +197,64 @@ public boolean isOpen() {
 	@Override
 	public void initializeNativeSession(Session session) {
 		super.initializeNativeSession(session);
+		if (isJetty94) {
+			initializeJetty94Session(session);
+		}
+		else {
+			initializeJettySession(session);
+		}
+	}
+
+	@SuppressWarnings("unchecked")
+	private void initializeJettySession(Session session) {
+
+		Object request = ReflectionUtils.invokeMethod(getUpgradeRequest, session);
+		Object response = ReflectionUtils.invokeMethod(getUpgradeResponse, session);
 
+		this.id = ObjectUtils.getIdentityHexString(getNativeSession());
+		this.uri = (URI) ReflectionUtils.invokeMethod(getRequestURI, request);
+
+		this.headers = new HttpHeaders();
+		this.headers.putAll((Map<String, List<String>>) ReflectionUtils.invokeMethod(getHeaders, request));
+		this.headers = HttpHeaders.readOnlyHttpHeaders(headers);
+
+		this.acceptedProtocol = (String) ReflectionUtils.invokeMethod(getAcceptedSubProtocol, response);
+
+		List<ExtensionConfig> source = (List<ExtensionConfig>) ReflectionUtils.invokeMethod(getExtensions, response);
+		if (source != null) {
+			this.extensions = new ArrayList<WebSocketExtension>(source.size());
+			for (ExtensionConfig ec : source) {
+				this.extensions.add(new WebSocketExtension(ec.getName(), ec.getParameters()));
+			}
+		}
+		else {
+			this.extensions = new ArrayList<WebSocketExtension>(0);
+		}
+
+		if (this.user == null) {
+			this.user = (Principal) ReflectionUtils.invokeMethod(getUserPrincipal, request);
+		}
+	}
+
+	private void initializeJetty94Session(Session session) {
 		this.id = ObjectUtils.getIdentityHexString(getNativeSession());
 		this.uri = session.getUpgradeRequest().getRequestURI();
 
 		this.headers = new HttpHeaders();
-		this.headers.putAll(getNativeSession().getUpgradeRequest().getHeaders());
+		this.headers.putAll(session.getUpgradeRequest().getHeaders());
 		this.headers = HttpHeaders.readOnlyHttpHeaders(headers);
 
 		this.acceptedProtocol = session.getUpgradeResponse().getAcceptedSubProtocol();
 
 		List<ExtensionConfig> source = getNativeSession().getUpgradeResponse().getExtensions();
-		this.extensions = new ArrayList<WebSocketExtension>(source.size());
-		for (ExtensionConfig ec : source) {
-			this.extensions.add(new WebSocketExtension(ec.getName(), ec.getParameters()));
+		if (source != null) {
+			this.extensions = new ArrayList<WebSocketExtension>(source.size());
+			for (ExtensionConfig ec : source) {
+				this.extensions.add(new WebSocketExtension(ec.getName(), ec.getParameters()));
+			}
+		}
+		else {
+				this.extensions = new ArrayList<WebSocketExtension>(0);
 		}
 
 		if (this.user == null) {