BAEL-252(A Java Client to consume a WebSockets API) (#1791)

* @BAEL-252 - Initial checkin

* BAEL-252 : Added junit tests

spring-boot/pom.xml

@@ -126,6 +126,18 @@
             <version>6.0.6</version>
         </dependency>
 
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-websocket</artifactId>
+            <version>${spring.version}</version>
+        </dependency>
+      
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-messaging</artifactId>
+            <version>${spring.version}</version>
+         </dependency>
+      
          <dependency>
             <groupId>org.togglz</groupId>
             <artifactId>togglz-spring-boot-starter</artifactId>

spring-boot/src/main/java/org/baeldung/websocket/client/Message.java

@@ -0,0 +1,25 @@
+package org.baeldung.websocket.client;
+
+public class Message {
+
+    private String from;
+    private String text;
+
+    public String getText() {
+        return text;
+    }
+
+    public String getFrom() {
+        return from;
+    }
+
+    public void setFrom(String from) {
+        this.from = from;
+    }
+
+    public void setText(String text) {
+        this.text = text;
+    }
+    
+    
+}

spring-boot/src/main/java/org/baeldung/websocket/client/MyStompSessionHandler.java

@@ -0,0 +1,58 @@
+package org.baeldung.websocket.client;
+
+import org.apache.log4j.Logger;
+import org.springframework.messaging.simp.stomp.StompCommand;
+import org.springframework.messaging.simp.stomp.StompHeaders;
+import org.springframework.messaging.simp.stomp.StompSession;
+import org.springframework.messaging.simp.stomp.StompSessionHandlerAdapter;
+
+import java.lang.reflect.Type;
+
+/**
+ * This class is an implementation for <code>StompSessionHandlerAdapter</code>.
+ * Once a connection is established, We subscribe to /topic/messages and 
+ * send a sample message to server.
+ * 
+ * @author Kalyan
+ *
+ */
+public class MyStompSessionHandler extends StompSessionHandlerAdapter {
+    
+    private Logger logger = Logger.getLogger(MyStompSessionHandler.class);
+    
+    @Override
+    public void afterConnected(StompSession session, StompHeaders connectedHeaders) {
+        logger.info("New session established : "+session.getSessionId());
+        session.subscribe("/topic/messages", this);
+        logger.info("Subscribed to /topic/messages");
+        session.send("/app/chat", getSampleMessage());
+        logger.info("Message sent to websocket server");
+    }
+
+    @Override
+    public void handleException(StompSession session, StompCommand command, StompHeaders headers, byte[] payload, Throwable exception) {
+        logger.error("Got an exception", exception);
+    }
+
+    @Override
+    public Type getPayloadType(StompHeaders headers) {
+        return Message.class;
+    }
+
+    @Override
+    public void handleFrame(StompHeaders headers, Object payload) {
+        Message msg = (Message)payload;
+        logger.info("Received : "+ msg.getText()+ " from : "+msg.getFrom());
+    }
+    
+    /**
+     * A sample message instance.
+     * @return instance of <code>Message</code>
+     */
+    private Message getSampleMessage(){
+        Message msg = new Message();
+        msg.setFrom("Nicky");
+        msg.setText("Howdy!!");
+        return msg;
+    }
+}

spring-boot/src/main/java/org/baeldung/websocket/client/StompClient.java

@@ -0,0 +1,37 @@
+package org.baeldung.websocket.client;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Scanner;
+
+import org.springframework.messaging.converter.MappingJackson2MessageConverter;
+import org.springframework.messaging.simp.stomp.StompSessionHandler;
+import org.springframework.web.socket.client.standard.StandardWebSocketClient;
+import org.springframework.web.socket.messaging.WebSocketStompClient;
+import org.springframework.web.socket.sockjs.client.SockJsClient;
+import org.springframework.web.socket.sockjs.client.Transport;
+import org.springframework.web.socket.sockjs.client.WebSocketTransport;
+
+/**
+ * Stand alone WebSocketStompClient.
+ * @author Kalyan
+ *
+ */
+public class StompClient {
+
+    private static String URL = "ws://localhost:8080/spring-mvc-java/chat";
+
+    public static void main(String[] args) {
+        Transport webSocketTransport = new WebSocketTransport(new StandardWebSocketClient());
+        List<Transport> transports = Collections.singletonList(webSocketTransport);
+        SockJsClient sockJsClient = new SockJsClient(transports);
+
+        WebSocketStompClient stompClient = new WebSocketStompClient(sockJsClient);
+        stompClient.setMessageConverter(new MappingJackson2MessageConverter());
+
+        StompSessionHandler sessionHandler = new MyStompSessionHandler();
+        stompClient.connect(URL, sessionHandler);
+
+        new Scanner(System.in).nextLine(); // Don't close immediately.
+    }
+}

spring-boot/src/test/java/com/baeldung/websocket/client/MyStompSessionHandlerTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.websocket.client;
+
+import org.baeldung.websocket.client.MyStompSessionHandler;
+import org.junit.Test;
+import org.mockito.Mockito;
+import org.springframework.messaging.simp.stomp.StompHeaders;
+import org.springframework.messaging.simp.stomp.StompSession;
+
+/**
+ * Test class for MyStompSessionHandler
+ * @author Kalyan
+ *
+ */
+public class MyStompSessionHandlerTest {
+
+    @Test
+    public void testAfterConnectedSuccessfull() {
+        StompSession mockSession = Mockito.mock(StompSession.class);
+        StompHeaders mockHeader = Mockito.mock(StompHeaders.class);
+        MyStompSessionHandler sessionHandler = new MyStompSessionHandler();
+        sessionHandler.afterConnected(mockSession, mockHeader);
+        Mockito.verify(mockSession).subscribe("/topic/messages", sessionHandler);
+        Mockito.verify(mockSession).send(Mockito.anyString(), Mockito.anyObject());
+    }
+}
+