GH-3533: Register WebSocket endpoints at runtime (#3548)

* GH-3533: Register WebSocket endpoints at runtime

Fixes https://github.com/spring-projects/spring-integration/issues/3533

* Rework `WebSocketIntegrationConfigurationInitializer` to register beans functional way
to avoid reflection for Spring Native support
* Move `IntegrationServletWebSocketHandlerRegistry` into a separate file for better readability
* Implement `DestructionAwareBeanPostProcessor` for `IntegrationServletWebSocketHandlerRegistry`
to track runtime bean registrations and removals
* Introduce an `IntegrationDynamicWebSocketHandlerMapping` to manage runtime mapping
registrations and removals
* Add `servlet-api` dependency into `websocket` to be able to compile an
`IntegrationDynamicWebSocketHandlerMapping`
* Fix typo in the exception message of the `StandardIntegrationFlowRegistration`
* Start dynamically added beans together with associated `IntegrationFlow` in the
`StandardIntegrationFlowContext`
* Document new feature

* * Fix language in docs
* Don't start those `SmartLifecycle`s together with a dynamic flow
which are not `isAutoStartup()`

* * Fix `TomcatWebSocketTestServer` to configure servlet for `loadOnStartup = 1`
* Fix `WebSocketDslTests` to make `clientWebSocketContainer.setAutoStartup(true)`

spring-integration-websocket/src/test/java/org/springframework/integration/websocket/TomcatWebSocketTestServer.java

@@ -20,6 +20,7 @@ import java.io.File;
 import java.io.IOException;
 
 import org.apache.catalina.Context;
+import org.apache.catalina.Wrapper;
 import org.apache.catalina.startup.Tomcat;
 import org.apache.tomcat.websocket.server.WsContextListener;
 
@@ -49,8 +50,10 @@ public class TomcatWebSocketTestServer implements InitializingBean, DisposableBe
 
 		Context context = this.tomcatServer.addContext("", System.getProperty("java.io.tmpdir"));
 		context.addApplicationListener(WsContextListener.class.getName());
-		Tomcat.addServlet(context, "dispatcherServlet", new DispatcherServlet(this.serverContext))
-				.setAsyncSupported(true);
+		Wrapper dispatcherServlet =
+				Tomcat.addServlet(context, "dispatcherServlet", new DispatcherServlet(this.serverContext));
+		dispatcherServlet.setAsyncSupported(true);
+		dispatcherServlet.setLoadOnStartup(1);
 		context.addServletMappingDecoded("/", "dispatcherServlet");
 	}
 

spring-integration-websocket/src/test/java/org/springframework/integration/websocket/dsl/WebSocketDslTests.java

@@ -0,0 +1,147 @@
+/*
+ * Copyright 2021 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
+ *
+ *      https://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 org.springframework.integration.websocket.dsl;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+
+import javax.websocket.DeploymentException;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.integration.channel.QueueChannel;
+import org.springframework.integration.config.EnableIntegration;
+import org.springframework.integration.dsl.IntegrationFlow;
+import org.springframework.integration.dsl.IntegrationFlows;
+import org.springframework.integration.dsl.context.IntegrationFlowContext;
+import org.springframework.integration.websocket.ClientWebSocketContainer;
+import org.springframework.integration.websocket.ServerWebSocketContainer;
+import org.springframework.integration.websocket.TomcatWebSocketTestServer;
+import org.springframework.integration.websocket.inbound.WebSocketInboundChannelAdapter;
+import org.springframework.integration.websocket.outbound.WebSocketOutboundMessageHandler;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageHandlingException;
+import org.springframework.messaging.support.GenericMessage;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
+import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
+import org.springframework.web.socket.client.WebSocketClient;
+import org.springframework.web.socket.client.standard.StandardWebSocketClient;
+import org.springframework.web.socket.server.HandshakeHandler;
+import org.springframework.web.socket.server.standard.TomcatRequestUpgradeStrategy;
+import org.springframework.web.socket.server.support.DefaultHandshakeHandler;
+
+@SpringJUnitConfig(classes = WebSocketDslTests.ClientConfig.class)
+@DirtiesContext
+public class WebSocketDslTests {
+
+	@Autowired
+	TomcatWebSocketTestServer server;
+
+	@Autowired
+	WebSocketClient webSocketClient;
+
+	@Autowired
+	IntegrationFlowContext integrationFlowContext;
+
+	@Test
+	void testDynamicServerEndpointRegistration() {
+		// Dynamic server flow
+		AnnotationConfigWebApplicationContext serverContext = this.server.getServerContext();
+		IntegrationFlowContext serverIntegrationFlowContext = serverContext.getBean(IntegrationFlowContext.class);
+		ServerWebSocketContainer serverWebSocketContainer =
+				new ServerWebSocketContainer("/dynamic")
+						.setHandshakeHandler(serverContext.getBean(HandshakeHandler.class));
+
+		WebSocketInboundChannelAdapter webSocketInboundChannelAdapter =
+				new WebSocketInboundChannelAdapter(serverWebSocketContainer);
+
+		QueueChannel dynamicRequestsChannel = new QueueChannel();
+
+		IntegrationFlow serverFlow =
+				IntegrationFlows.from(webSocketInboundChannelAdapter)
+						.channel(dynamicRequestsChannel)
+						.get();
+
+		IntegrationFlowContext.IntegrationFlowRegistration dynamicServerFlow =
+				serverIntegrationFlowContext.registration(serverFlow)
+						.addBean(serverWebSocketContainer)
+						.register();
+
+		// Dynamic client flow
+		ClientWebSocketContainer clientWebSocketContainer =
+				new ClientWebSocketContainer(this.webSocketClient, this.server.getWsBaseUrl() + "/dynamic");
+		clientWebSocketContainer.setAutoStartup(true);
+		WebSocketOutboundMessageHandler webSocketOutboundMessageHandler =
+				new WebSocketOutboundMessageHandler(clientWebSocketContainer);
+
+		IntegrationFlow clientFlow = flow -> flow.handle(webSocketOutboundMessageHandler);
+
+		IntegrationFlowContext.IntegrationFlowRegistration dynamicClientFlow =
+				this.integrationFlowContext.registration(clientFlow)
+						.addBean(clientWebSocketContainer)
+						.register();
+
+		dynamicClientFlow.getInputChannel().send(new GenericMessage<>("dynamic test"));
+
+		Message<?> result = dynamicRequestsChannel.receive(10_000);
+		assertThat(result).isNotNull()
+				.extracting(Message::getPayload)
+				.isEqualTo("dynamic test");
+
+		dynamicServerFlow.destroy();
+
+		assertThatExceptionOfType(MessageHandlingException.class)
+				.isThrownBy(() -> dynamicClientFlow.getInputChannel().send(new GenericMessage<>("another test")))
+				.withCauseInstanceOf(DeploymentException.class)
+				.withMessageContaining("The HTTP response from the server [404]");
+
+		dynamicClientFlow.destroy();
+	}
+
+	@Configuration
+	@EnableIntegration
+	public static class ClientConfig {
+
+		@Bean
+		public TomcatWebSocketTestServer server() {
+			return new TomcatWebSocketTestServer(WebSocketDslTests.ServerConfig.class);
+		}
+
+		@Bean
+		public WebSocketClient webSocketClient() {
+			return new StandardWebSocketClient();
+		}
+
+	}
+
+
+	@Configuration
+	@EnableIntegration
+	static class ServerConfig {
+
+		@Bean
+		public DefaultHandshakeHandler handshakeHandler() {
+			return new DefaultHandshakeHandler(new TomcatRequestUpgradeStrategy());
+		}
+
+	}
+
+}