Introduce SubProtocolHandler abstraction

Add SubProtocolHandler to encapsulate the logic for using a
sub-protocol.

A SubProtocolWebSocketHandler is also provided to
delegate to the appropriate SubProtocolHandler based on the
negotiated sub-protocol value at handshake.

StompSubProtocolHandler provides handling for STOMP messages.

Issue: SPR-10786

spring-messaging/src/test/java/org/springframework/messaging/handler/websocket/SubProtocolWebSocketHandlerTests.java

@@ -0,0 +1,127 @@
+/*
+ * Copyright 2002-2013 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 CONDITIOsNS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.messaging.handler.websocket;
+
+import java.util.Arrays;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.springframework.messaging.MessageChannel;
+import org.springframework.web.socket.support.TestWebSocketSession;
+
+import static org.mockito.Mockito.*;
+
+
+/**
+ * Test fixture for {@link SubProtocolWebSocketHandler}.
+ *
+ * @author Rossen Stoyanchev
+ * @author Andy Wilkinson
+ */
+public class SubProtocolWebSocketHandlerTests {
+
+	private SubProtocolWebSocketHandler webSocketHandler;
+
+	private TestWebSocketSession session;
+
+	@Mock
+	SubProtocolHandler stompHandler;
+
+	@Mock
+	SubProtocolHandler mqttHandler;
+
+	@Mock
+	SubProtocolHandler defaultHandler;
+
+	@Mock
+	MessageChannel channel;
+
+
+	@Before
+	public void setup() {
+		MockitoAnnotations.initMocks(this);
+
+		this.webSocketHandler = new SubProtocolWebSocketHandler(this.channel);
+		when(stompHandler.getSupportedProtocols()).thenReturn(Arrays.asList("STOMP"));
+		when(mqttHandler.getSupportedProtocols()).thenReturn(Arrays.asList("MQTT"));
+
+		this.session = new TestWebSocketSession();
+		this.session.setId("1");
+	}
+
+
+	@Test
+	public void subProtocolMatch() throws Exception {
+		this.webSocketHandler.setProtocolHandlers(Arrays.asList(stompHandler, mqttHandler));
+		this.session.setAcceptedProtocol("sToMp");
+		this.webSocketHandler.afterConnectionEstablished(session);
+
+		verify(this.stompHandler).afterSessionStarted(session, this.channel);
+		verify(this.mqttHandler, times(0)).afterSessionStarted(session, this.channel);
+	}
+
+	@Test
+	public void subProtocolDefaultHandlerOnly() throws Exception {
+		this.webSocketHandler.setDefaultProtocolHandler(stompHandler);
+		this.session.setAcceptedProtocol("sToMp");
+		this.webSocketHandler.afterConnectionEstablished(session);
+
+		verify(this.stompHandler).afterSessionStarted(session, this.channel);
+	}
+
+	@Test(expected=IllegalStateException.class)
+	public void subProtocolNoMatch() throws Exception {
+		this.webSocketHandler.setDefaultProtocolHandler(defaultHandler);
+		this.webSocketHandler.setProtocolHandlers(Arrays.asList(stompHandler, mqttHandler));
+		this.session.setAcceptedProtocol("wamp");
+
+		this.webSocketHandler.afterConnectionEstablished(session);
+	}
+
+	@Test
+	public void noSubProtocol() throws Exception {
+		this.webSocketHandler.setDefaultProtocolHandler(defaultHandler);
+		this.webSocketHandler.afterConnectionEstablished(session);
+
+		verify(this.defaultHandler).afterSessionStarted(session, this.channel);
+		verify(this.stompHandler, times(0)).afterSessionStarted(session, this.channel);
+		verify(this.mqttHandler, times(0)).afterSessionStarted(session, this.channel);
+	}
+
+	@Test
+	public void noSubProtocolOneHandler() throws Exception {
+		this.webSocketHandler.setProtocolHandlers(Arrays.asList(stompHandler));
+		this.webSocketHandler.afterConnectionEstablished(session);
+
+		verify(this.stompHandler).afterSessionStarted(session, this.channel);
+	}
+
+	@Test(expected=IllegalStateException.class)
+	public void noSubProtocolTwoHandlers() throws Exception {
+		this.webSocketHandler.setProtocolHandlers(Arrays.asList(stompHandler, mqttHandler));
+		this.webSocketHandler.afterConnectionEstablished(session);
+	}
+
+	@Test(expected=IllegalStateException.class)
+	public void noSubProtocolNoDefaultHandler() throws Exception {
+		this.webSocketHandler.setProtocolHandlers(Arrays.asList(stompHandler, mqttHandler));
+		this.webSocketHandler.afterConnectionEstablished(session);
+	}
+
+}