1/ 概述

利用Spring Boot作为基础框架，Spring Security作为安全框架，WebSocket作为通信框架，实现点对点聊天和群聊天。

2/ 所需依赖

Spring Boot 版本 1.5.3，使用MongoDB存储数据（非必须），Maven依赖如下：

<properties>
    <java.version>1.8</java.version>
    <thymeleaf.version>3.0.0.RELEASE</thymeleaf.version>
    <thymeleaf-layout-dialect.version>2.0.0</thymeleaf-layout-dialect.version>
  </properties>

  <dependencies>

    <!-- WebSocket依赖，移除Tomcat容器 -->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-websocket</artifactId>
      <exclusions>
        <exclusion>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
      </exclusions>
    </dependency>

    <!-- 使用Undertow容器 -->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-undertow</artifactId>
    </dependency>

    <!--  Spring Security 框架 -->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-security</artifactId>
    </dependency>

    <!-- MongoDB数据库 -->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-data-mongodb</artifactId>
    </dependency>

    <!-- Thymeleaf 模版引擎 -->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-thymeleaf</artifactId>
    </dependency>

    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <version>1.16.16</version>
    </dependency>

    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>fastjson</artifactId>
      <version>1.2.30</version>
    </dependency>

    <!-- 静态资源 -->
    <dependency>
      <groupId>org.webjars</groupId>
      <artifactId>webjars-locator</artifactId>
    </dependency>
    <dependency>
      <groupId>org.webjars</groupId>
      <artifactId>sockjs-client</artifactId>
      <version>1.0.2</version>
    </dependency>
    <dependency>
      <groupId>org.webjars</groupId>
      <artifactId>stomp-websocket</artifactId>
      <version>2.3.3</version>
    </dependency>
    <dependency>
      <groupId>org.webjars</groupId>
      <artifactId>bootstrap</artifactId>
      <version>3.3.7</version>
    </dependency>
    <dependency>
      <groupId>org.webjars</groupId>
      <artifactId>jquery</artifactId>
      <version>3.1.0</version>
    </dependency>

  </dependencies>

配置文件内容：

server:
  port: 80

# 若使用MongoDB则配置如下参数
spring:
  data:
    mongodb:
      uri: mongodb://username:password@172.25.11.228:27017
      authentication-database: admin
      database: chat

大致程序结构，仅供参考：

程序结构

3/ 创建程序启动类，启用WebSocket

使用@EnableWebSocket注解

@SpringBootApplication
@EnableWebSocket
public class Application {

 public static void main(String[] args) {
    SpringApplication.run(Application.class, args);
 }

}

4/ 配置Spring Security

此章节省略。（配置好Spring Security，用户能正常登录即可）可以参考：Spring Boot 全栈开发：用户安全

5/ 配置Web Socket（结合第7节的JS看）

@Configuration
@EnableWebSocketMessageBroker
@Log4j
public class WebSocketConfig extends AbstractWebSocketMessageBrokerConfigurer {

  // 此处可注入自己写的Service

  @Override
  public void registerStompEndpoints(StompEndpointRegistry stompEndpointRegistry) {
    // 客户端与服务器端建立连接的点
    stompEndpointRegistry.addEndpoint("/any-socket").withSockJS();
  }

  @Override
  public void configureMessageBroker(MessageBrokerRegistry messageBrokerRegistry) {
    // 配置客户端发送信息的路径的前缀
    messageBrokerRegistry.setApplicationDestinationPrefixes("/app");
    messageBrokerRegistry.enableSimpleBroker("/topic");
  }

  @Override
  public void configureWebSocketTransport(final WebSocketTransportRegistration registration) {
    registration.addDecoratorFactory(new WebSocketHandlerDecoratorFactory() {
      @Override
      public WebSocketHandler decorate(final WebSocketHandler handler) {
        return new WebSocketHandlerDecorator(handler) {
          @Override
          public void afterConnectionEstablished(final WebSocketSession session) throws Exception {
            // 客户端与服务器端建立连接后，此处记录谁上线了
            String username = session.getPrincipal().getName();
            log.info("online: " + username);
            super.afterConnectionEstablished(session);
          }

          @Override
          public void afterConnectionClosed(WebSocketSession session, CloseStatus closeStatus) throws Exception {
            // 客户端与服务器端断开连接后，此处记录谁下线了
            String username = session.getPrincipal().getName();
            log.info("offline: " + username);
            super.afterConnectionClosed(session, closeStatus);
          }
        };
      }
    });
    super.configureWebSocketTransport(registration);
  }
}

6/ 点对点消息，群消息

@Controller
@Log4j
public class ChatController {

  @Autowired
  private SimpMessagingTemplate template;

  // 注入其它Service

  // 群聊天
  @MessageMapping("/notice")
  public void notice(Principal principal, String message) {  
    // 参数说明 principal 当前登录的用户， message 客户端发送过来的内容
    // principal.getName() 可获得当前用户的username  

    // 发送消息给订阅 "/topic/notice" 且在线的用户
    template.convertAndSend("/topic/notice", message); 
  }

  // 点对点聊天
  @MessageMapping("/chat")
  public void chat(Principal principal, String message){
    // 参数说明 principal 当前登录的用户， message 客户端发送过来的内容（应该至少包含发送对象toUser和消息内容content）
    // principal.getName() 可获得当前用户的username

    // 发送消息给订阅 "/user/topic/chat" 且用户名为toUser的用户
    template.convertAndSendToUser(toUser, "/topic/chat", content);
  }

}

7/ 客户端与服务器端交互

var stompClient = null;

    function connect() {
        var socket = new SockJS('/any-socket');
        stompClient = Stomp.over(socket);
        stompClient.connect({}, function (frame) {
            // 订阅 /topic/notice 实现群聊
            stompClient.subscribe('/topic/notice', function (message) {
                showMessage(JSON.parse(message.body));
            });
            // 订阅 /user/topic/chat 实现点对点聊
            stompClient.subscribe('/user/topic/chat', function (message) {
                showMessage(JSON.parse(message.body));
            });
        });
    }

    function showMessage(message) {
        // 处理消息在页面的显示
    }

    $(function () {
        // 建立websocket连接
        connect();
        // 发送消息按钮事件
        $("#send").click(function () {
            if (target == "TO_ALL"){
                // 群发消息
                // 匹配后端ChatController中的 @MessageMapping("/notice")
                stompClient.send("/app/notice", {}, '消息内容');
            }else{
                // 点对点消息，消息中必须包含对方的username
                // 匹配后端ChatController中的 @MessageMapping("/chat")
                var content = "{'content':'消息内容','receiver':'anoy'}";
                stompClient.send("/app/chat", {}, content);
            }
        });
    });