Work around Jetty websocket client bug

Add workaround for Jetty JsrSession NullPointerException bug
(https://github.com/eclipse/jetty.project/issues/1202) in
`spring-boot-sample-websocket-jetty`.

See gh-7599

spring-boot-samples/spring-boot-sample-websocket-jetty/src/test/java/samples/websocket/jetty/SampleWebSocketsApplicationTests.java

@@ -22,8 +22,10 @@ import java.util.concurrent.atomic.AtomicReference;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.eclipse.jetty.websocket.jsr356.ClientContainer;
 import org.junit.Test;
 import org.junit.runner.RunWith;
+import samples.websocket.jetty.client.FixedClientContainer;
 import samples.websocket.jetty.client.GreetingService;
 import samples.websocket.jetty.client.SimpleClientWebSocketHandler;
 import samples.websocket.jetty.client.SimpleGreetingService;
@@ -108,7 +110,7 @@ public class SampleWebSocketsApplicationTests {
 		}
 
 		@Bean
-		public WebSocketConnectionManager wsConnectionManager() {
+		public WebSocketConnectionManager wsConnectionManager() throws Exception {
 
 			WebSocketConnectionManager manager = new WebSocketConnectionManager(client(),
 					handler(), this.webSocketUri);
@@ -118,8 +120,10 @@ public class SampleWebSocketsApplicationTests {
 		}
 
 		@Bean
-		public StandardWebSocketClient client() {
+		public StandardWebSocketClient client() throws Exception {
-			return new StandardWebSocketClient();
+			ClientContainer clientContainer = new FixedClientContainer();
+			clientContainer.start();
+			return new StandardWebSocketClient(clientContainer);
 		}
 
 		@Bean

spring-boot-samples/spring-boot-sample-websocket-jetty/src/test/java/samples/websocket/jetty/client/FixedClientContainer.java

@@ -0,0 +1,87 @@
+/*
+ * 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 samples.websocket.jetty.client;
+
+import java.net.URI;
+import java.util.Collections;
+import java.util.List;
+
+import javax.websocket.Extension;
+
+import org.eclipse.jetty.websocket.client.WebSocketClient;
+import org.eclipse.jetty.websocket.common.LogicalConnection;
+import org.eclipse.jetty.websocket.common.WebSocketSession;
+import org.eclipse.jetty.websocket.common.events.EventDriver;
+import org.eclipse.jetty.websocket.jsr356.ClientContainer;
+import org.eclipse.jetty.websocket.jsr356.JsrSession;
+import org.eclipse.jetty.websocket.jsr356.JsrSessionFactory;
+
+import org.springframework.test.util.ReflectionTestUtils;
+
+/**
+ * Jetty {@link ClientContainer} to work around
+ * https://github.com/eclipse/jetty.project/issues/1202.
+ *
+ * @author Phillip Webb
+ */
+public class FixedClientContainer extends ClientContainer {
+
+	public FixedClientContainer() {
+		super();
+		WebSocketClient client = getClient();
+		ReflectionTestUtils.setField(client, "sessionFactory",
+				new FixedJsrSessionFactory(this));
+	}
+
+	private static class FixedJsrSessionFactory extends JsrSessionFactory {
+
+		private final ClientContainer container;
+
+		public FixedJsrSessionFactory(ClientContainer container) {
+			super(container);
+			this.container = container;
+		}
+
+		@Override
+		public WebSocketSession createSession(URI requestURI, EventDriver websocket,
+				LogicalConnection connection) {
+			return new FixedJsrSession(this.container, connection.getId(), requestURI,
+					websocket, connection);
+		}
+
+	}
+
+	private static class FixedJsrSession extends JsrSession {
+
+		public FixedJsrSession(ClientContainer container, String id, URI requestURI,
+				EventDriver websocket, LogicalConnection connection) {
+			super(container, id, requestURI, websocket, connection);
+		}
+
+		@Override
+		public List<Extension> getNegotiatedExtensions() {
+			try {
+				return super.getNegotiatedExtensions();
+			}
+			catch (NullPointerException ex) {
+				return Collections.emptyList();
+			}
+		}
+
+	}
+
+}

spring-boot-samples/spring-boot-sample-websocket-jetty/src/test/java/samples/websocket/jetty/echo/CustomContainerWebSocketsApplicationTests.java

@@ -22,9 +22,11 @@ import java.util.concurrent.atomic.AtomicReference;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.eclipse.jetty.websocket.jsr356.ClientContainer;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import samples.websocket.jetty.SampleJettyWebSocketsApplication;
+import samples.websocket.jetty.client.FixedClientContainer;
 import samples.websocket.jetty.client.GreetingService;
 import samples.websocket.jetty.client.SimpleClientWebSocketHandler;
 import samples.websocket.jetty.client.SimpleGreetingService;
@@ -123,18 +125,18 @@ public class CustomContainerWebSocketsApplicationTests {
 		}
 
 		@Bean
-		public WebSocketConnectionManager wsConnectionManager() {
+		public WebSocketConnectionManager wsConnectionManager() throws Exception {
-
 			WebSocketConnectionManager manager = new WebSocketConnectionManager(client(),
 					handler(), this.webSocketUri);
 			manager.setAutoStartup(true);
-
 			return manager;
 		}
 
 		@Bean
-		public StandardWebSocketClient client() {
+		public StandardWebSocketClient client() throws Exception {
-			return new StandardWebSocketClient();
+			ClientContainer container = new FixedClientContainer();
+			container.start();
+			return new StandardWebSocketClient(container);
 		}
 
 		@Bean