Refactor reactive WebSocketClient contract

Switch from returning Mono<WebSocketSession> to take a WebSocketHandler
and return Mono<Void> for the entire session handling.

The WebSocketHandler callback delimits the stard and end of protocol
handling and forces the handler to operate within the scope of the
Reactor operators.

Give the full duplex nature of WebSockets, the symmetry between client
and server (each now using WebSocketHandler) also seems appropriate.

Issue: SPR-14527

spring-web-reactive/src/test/java/org/springframework/web/reactive/socket/server/AbstractWebSocketIntegrationTests.java

@@ -16,8 +16,11 @@
 package org.springframework.web.reactive.socket.server;
 
 import java.io.File;
+import java.net.URI;
+import java.net.URISyntaxException;
 
 import org.apache.tomcat.websocket.server.WsContextListener;
+import org.jetbrains.annotations.NotNull;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.runner.RunWith;
@@ -112,6 +115,12 @@ public abstract class AbstractWebSocketIntegrationTests {
 		}
 	}
 
+	@NotNull
+	protected URI getUrl(String path) throws URISyntaxException {
+		return new URI("ws://localhost:" + this.port + path);
+	}
+
+
 	static abstract class AbstractHandlerAdapterConfig {
 
 		@Bean

spring-web-reactive/src/test/java/org/springframework/web/reactive/socket/server/WebSocketIntegrationTests.java

@@ -15,13 +15,13 @@
  */
 package org.springframework.web.reactive.socket.server;
 
-import java.net.URI;
 import java.util.HashMap;
 import java.util.Map;
 
 import org.junit.Test;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
+import reactor.core.publisher.ReplayProcessor;
 
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -35,7 +35,6 @@ import static org.junit.Assert.assertEquals;
 
 /**
  * Integration tests with server-side {@link WebSocketHandler}s.
- *
  * @author Rossen Stoyanchev
  */
 @SuppressWarnings({"unused", "WeakerAccess"})
@@ -52,9 +51,10 @@ public class WebSocketIntegrationTests extends AbstractWebSocketIntegrationTests
 	public void echo() throws Exception {
 		int count = 100;
 		Flux<String> input = Flux.range(1, count).map(index -> "msg-" + index);
-		Flux<String> output = new RxNettyWebSocketClient()
-				.connect(new URI("ws://localhost:" + this.port + "/echo"))
-				.flatMap(session -> session
+		ReplayProcessor<Object> emitter = ReplayProcessor.create(count);
+
+		new RxNettyWebSocketClient()
+				.execute(getUrl("/echo"), session -> session
 						.send(input.map(session::textMessage))
 						.thenMany(session.receive()
 								.take(count)
@@ -62,9 +62,12 @@ public class WebSocketIntegrationTests extends AbstractWebSocketIntegrationTests
 									String text = message.getPayloadAsText();
 									message.release();
 									return text;
-								})
-						));
-		assertEquals(input.collectList().blockMillis(5000), output.collectList().blockMillis(5000));
+								}))
+						.subscribeWith(emitter)
+						.then())
+				.blockMillis(5000);
+
+		assertEquals(input.collectList().blockMillis(5000), emitter.collectList().blockMillis(5000));
 	}