Allow setting SockJsMessageCodec in WebSocket config

Issue: SPR-12091

spring-websocket/src/test/java/org/springframework/web/socket/config/HandlersBeanDefinitionParserTests.java

@@ -16,6 +16,8 @@
 
 package org.springframework.web.socket.config;
 
+import java.io.IOException;
+import java.io.InputStream;
 import java.util.Date;
 import java.util.List;
 import java.util.Map;
@@ -45,6 +47,7 @@ import org.springframework.web.socket.server.HandshakeInterceptor;
 import org.springframework.web.socket.server.support.DefaultHandshakeHandler;
 import org.springframework.web.socket.server.support.WebSocketHttpRequestHandler;
 import org.springframework.web.socket.sockjs.SockJsService;
+import org.springframework.web.socket.sockjs.frame.SockJsMessageCodec;
 import org.springframework.web.socket.sockjs.support.SockJsHttpRequestHandler;
 import org.springframework.web.socket.sockjs.transport.TransportHandler;
 import org.springframework.web.socket.sockjs.transport.TransportHandlingSockJsService;
@@ -218,6 +221,7 @@ public class HandlersBeanDefinitionParserTests {
 		assertEquals(256, transportService.getDisconnectDelay());
 		assertEquals(1024, transportService.getHttpMessageCacheSize());
 		assertEquals(20, transportService.getHeartbeatTime());
+		assertEquals(TestMessageCodec.class, transportService.getMessageCodec().getClass());
 	}
 
 	private void loadBeanDefinitions(String fileName) {
@@ -327,4 +331,22 @@ class TestTaskScheduler implements TaskScheduler {
 		return null;
 	}
 
+}
+
+class TestMessageCodec implements SockJsMessageCodec {
+
+	@Override
+	public String encode(String... messages) {
+		return null;
+	}
+
+	@Override
+	public String[] decode(String content) throws IOException {
+		return new String[0];
+	}
+
+	@Override
+	public String[] decodeInputStream(InputStream content) throws IOException {
+		return new String[0];
+	}
 }

spring-websocket/src/test/resources/org/springframework/web/socket/config/websocket-config-handlers-sockjs-attributes.xml

@@ -9,7 +9,7 @@
 		<websocket:mapping path="/test" handler="testHandler"/>
 		<websocket:sockjs name="testSockJsService" scheduler="testTaskScheduler" websocket-enabled="false"
 						  session-cookie-needed="false" stream-bytes-limit="2048" disconnect-delay="256"
-						  message-cache-size="1024" heartbeat-time="20">
+						  message-cache-size="1024" heartbeat-time="20" message-codec="messageCodec">
 			<websocket:transport-handlers register-defaults="false">
 				<bean class="org.springframework.web.socket.sockjs.transport.handler.XhrPollingTransportHandler"/>
 				<ref bean="xhrStreamingTransportHandler"/>
@@ -20,5 +20,6 @@
 	<bean id="testHandler" class="org.springframework.web.socket.config.TestWebSocketHandler"/>
 	<bean id="testTaskScheduler" class="org.springframework.web.socket.config.TestTaskScheduler"/>
 	<bean id="xhrStreamingTransportHandler" class="org.springframework.web.socket.sockjs.transport.handler.XhrStreamingTransportHandler"/>
+	<bean id="messageCodec" class="org.springframework.web.socket.config.TestMessageCodec" />
 
 </beans>