一、背景

项目中需要建立客户端与服务端之间的长链接，首先就考虑用WebSocket，再来SpringBoot原来整合WebSocket方式并不高效，因此找到了netty-websocket-spring-boot-starter 这款脚手架，它能让我们在SpringBoot中使用Netty来开发WebSocket服务器，并像spring-websocket的注解开发一样简单

二、netty-websocket-spring-boot-starter 入门介绍

2.1 核心注解

2.1.1 @ServerEndpoint

当ServerEndpointExporter类通过Spring配置进行声明并被使用，它将会去扫描带有@ServerEndpoint注解的类 被注解的类将被注册成为一个WebSocket端点 所有的配置项都在这个注解的属性中 ( 如:@ServerEndpoint(“/ws”) )

2.1.2 @OnOpen

当有新的WebSocket连接完成时，对该方法进行回调 注入参数的类型:Session、HttpHeaders…

2.1.3 @OnClose

当有WebSocket连接关闭时，对该方法进行回调 注入参数的类型:Session

2.1.4 @OnError

当有WebSocket抛出异常时，对该方法进行回调 注入参数的类型:Session、Throwable

2.1.5 @OnMessage

当接收到字符串消息时，对该方法进行回调 注入参数的类型:Session、String

2.2 核心配置

属性	属性说明
path	WebSocket的path,也可以用value来设置
host	WebSocket的host,"0.0.0.0"即是所有本地地址
port	WebSocket绑定端口号。如果为0，则使用随机端口(端口获取可见 多端点服务)
maxFramePayloadLength	最大允许帧载荷长度
allIdleTimeSeconds	与IdleStateHandler中的allIdleTimeSeconds一致，并且当它不为0时，将在pipeline中添加IdleStateHandler

三、实践netty-websocket-spring-boot-starter

3.1引入POM文件

主要添加包括以下依赖

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId>
</dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope>
</dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-redis</artifactId>
</dependency><dependency><groupId>org.yeauty</groupId><artifactId>netty-websocket-spring-boot-starter</artifactId><version>0.9.5</version>
</dependency><dependency><groupId>cn.hutool</groupId><artifactId>hutool-all</artifactId><version>5.4.6</version>
</dependency>

3.2 在主程序类中排除数据库使用

/*** 主程序启动类*/
@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})
public class WebsocketApplication {public static void main(String[] args) {SpringApplication.run(WebsocketApplication.class, args);}}

3.3 开启WebSocket支持

@Configuration
public class WebSocketConfig {@Beanpublic ServerEndpointExporter serverEndpointExporter() {return new ServerEndpointExporter();}
}

3.4 定义WebSocketServer服务器（核心代码）

在端点类上加上@ServerEndpoint注解，并在相应的方法上加上@OnOpen、@OnMessage、@OnError、@OnClose注解， 代码如下：

@ServerEndpoint(port = "${ws.port}", path = "/demo/{version}", maxFramePayloadLength = "6553600", allIdleTimeSeconds = "300")
public class WebSocketServer {private static Log LOGGER = LogFactory.get();// concurrent包的线程安全Set，用来存放每个客户端对应的MyWebSocket对象。private static CopyOnWriteArraySet<WebSocketServer> webSocketSet = new CopyOnWriteArraySet<WebSocketServer>();// 与某个客户端的连接会话，需要通过它来给客户端发送数据private Session session;// 接收用户IDprotected StringBuilder userInfo = new StringBuilder();@Autowiredprivate RedisTemplate<String, String> redisTemplate;/*** 连接建立成功调用的方法*/@OnOpenpublic void onOpen(Session session,HttpHeaders headers,@RequestParam String req,@RequestParam MultiValueMap<String, Object> reqMap,@PathVariable String arg,@PathVariable Map<String, Object> pathMap) {this.session = session;// 加入set中webSocketSet.add(this);// 在线数加1addOnlineCount();LOGGER.debug("UserId = {}, 通道ID={}, 当前连接人数={}", userInfo.toString(), getSessionId(session), getOnlineCount());}/*** 收到客户端消息后调用的方法*/@OnMessagepublic void onMessage(Session session, String message) {JSONObject jsonData = JSONUtil.parseObj(message);if (!jsonData.containsKey("command")) {LOGGER.debug("UserId = {}, 通道ID={}, 上行内容={}, 上行请求非法，缺少command参数, 处理结束",userInfo.toString(), getSessionId(session), message);return;}String userId = jsonData.getStr("userId");this.userInfo = new StringBuilder(userId);String command = jsonData.getStr("command");Class<?> service = Command.getService(command);if (Objects.isNull(service)) {errorMessage(command);LOGGER.error("UserId = {}, 通道ID={}, 解析指令执行出错！", userInfo.toString(), getSessionId(session));return;}LOGGER.info("UserId = {}, 通道ID={}, 处理类={}, 开始处理，请求内容={}",userInfo.toString(), getSessionId(session), service, jsonData.toString());BaseMessage baseMessage = getBaseMessage(service, session, command);if (baseMessage == null) {return;}try {jsonData.set("SessionId", getSessionId(session));JSON resp = baseMessage.handlerMessage(userInfo, jsonData);resp.putByPath("command", command);resp.putByPath("userId", userId);String value = resp.toString();//将结果写回客户端, 实现服务器主动推送ChannelFuture future = sendMessage(value);LOGGER.info("UserId = {}, 通道ID = {}, 返回内容 = {}, future = {}, 处理结束",userInfo.toString(), getSessionId(session), value, future.toString());} catch (Exception e) {LOGGER.error("UserId = {}, 通道ID={}, 解析执行出错信息={}", userInfo.toString(), getSessionId(session), e.getMessage());}}/*** 连接关闭调用的方法*/@OnClosepublic void onClose(Session session) {// 从set中删除webSocketSet.remove(this);// 在线数减1subOnlineCount();String userId = this.userInfo.toString();LOGGER.warn("UserId = {}, 通道ID = {}, 有一连接关闭！当前在线人数={}", userId, getSessionId(session), getOnlineCount());userInfo.delete(0, userInfo.length());if (ObjectUtil.isNotNull(userId)) {String keyStr = ConstDef.ONLINE_USER_TYPE + userId;redisTemplate.delete(keyStr);}session.close();}/*** 出错方法*/@OnErrorpublic void onError(Session session, Throwable cause) {if (Objects.nonNull(this.session) && Objects.nonNull(cause) && !(cause instanceof EOFException)) {LOGGER.error("UserId = {}, 通道ID={}, 出错信息={}", userInfo.toString(), this.session.id(), cause.toString());}if (Objects.nonNull(session) && session.isOpen()) {session.close();}}/*** 通过class获取Bean*/private BaseMessage getBaseMessage(Class<?> service, Session session, String command) {BaseMessage baseMessage;try {baseMessage = (BaseMessage) SpringUtils.getBean(service);} catch (Exception e) {LOGGER.error("UserId = {}, 通道ID = {}, 未找到协议头 = {} 的处理类", userInfo.toString(), getSessionId(session), service);errorMessage(command);return null;}return baseMessage;}/*** 获取通道ID*/private String getSessionId(Session session) {return session.id().asShortText();}/*** 协议错误*/public void errorMessage(String command) {JSONObject retObj = new JSONObject();retObj.set("code", ConstDef.ERROR_CODE_10001);retObj.set("msg", ConstDef.ERROR_CODE_10001_DESP);retObj.set("command", command);try {sendMessage(retObj.toString());} catch (IOException e) {LOGGER.error("UserId = {}, 通道ID={}, 解析执行出错信息={}", userInfo.toString(), getSessionId(session), e.getMessage());}}/*** 实现服务器主动推送*/public ChannelFuture sendMessage(String message) throws IOException {return this.session.sendText(message);}/*** 在线用户数*/public long getOnlineCount() {String onlineCountValue = redisTemplate.opsForValue().get(ConstDef.ONLINE_COUNT_KEY);if (StrUtil.isBlank(onlineCountValue) || !NumberUtil.isNumber(onlineCountValue)) {return 0L;}return Long.parseLong(onlineCountValue);}/*** 在线数+1*/private void addOnlineCount() {redisTemplate.opsForValue().increment(ConstDef.ONLINE_COUNT_KEY);}/*** 在线数-1*/private void subOnlineCount() {redisTemplate.opsForValue().decrement(ConstDef.ONLINE_COUNT_KEY);}
}

3.5 定义接口

/*** 消息处理接口*/
public interface BaseMessage {Log LOGGER = LogFactory.get();/*** 处理类、处理方法*/JSON handlerMessage(StringBuilder vin, JSONObject jsonData);
}

3.6 定义接口实现类 （业务处理逻辑）

该类是各业务的处理逻辑类，是接口类的具体实现。

@Component
@Configuration
public class QueryAllActivityListMessage implements BaseMessage {@Overridepublic JSON handlerMessage(StringBuilder userId, JSONObject jsonData) {LOGGER.debug("开始处理QueryAllActivityListMessage请求, 参数={}", JSONUtil.toJsonStr(jsonData));String resp = "我是服务器端返回的处理结果！";LOGGER.info("UserId = {}, param={}, QueryAllActivityListMessage回复 = {}", userId.toString(), jsonData, resp);JSONObject respStr = new JSONObject();return respStr.set("handleResult", resp);}
}

3.7 定义枚举Command

每增加一个业务接口的实现，就需要在这个枚举类注册一下。

/*** 指令-服务 枚举*/
public enum Command {/*** 业务1处理逻辑*/queryAllActivityList("queryAllActivityList", QueryAllActivityListMessage.class, "业务1处理逻辑");/*** 业务2处理逻辑*///略/*** 业务3处理逻辑*///略/*** 服务编码*/private String processCode;/*** 服务接口类*/private Class<?> service;/*** 接口描述*/private String desc;Command(String processCode, Class<?> service, String desc) {this.processCode = processCode;this.service = service;this.desc = desc;}public Class<?> getService() {return service;}public static Class<?> getService(String processCode) {for (Command command : Command.values()) {if (command.processCode.equals(processCode)) {return command.getService();}}return null;}
}

3.8 编写SpringUtils 工具类

用于搜索Bean， 通过class获取Bean

/*** SpringUtils 工具类，用于搜索*/
@Component
public class SpringUtils implements ApplicationContextAware {private static ApplicationContext applicationContext;@Overridepublic void setApplicationContext(ApplicationContext applicationContext) throws BeansException {if (SpringUtils.applicationContext == null) {SpringUtils.applicationContext = applicationContext;}}/*** 获取applicationContext*/public static ApplicationContext getApplicationContext() {return applicationContext;}/*** 通过class获取Bean*/public static <T> T getBean(Class<T> clazz) {return getApplicationContext().getBean(clazz);}/*** 通过name获取 Bean.*/public static Object getBean(String name) {return getApplicationContext().getBean(name);}/*** 通过name,以及Clazz返回指定的Bean*/public static <T> T getBean(String name, Class<T> clazz) {return getApplicationContext().getBean(name, clazz);}}

3.9 定义常量定义类 + 返回码

/*** 常量定义类 + 返回码*/
public class ConstDef {/*** 返回码*/public static final int ERROR_CODE_10001 = 10001;public static final String ERROR_CODE_10001_DESP = "请求参数不合法";/*** 按UserId决定，用户在线类型，车机或者手机*/public static final String ONLINE_USER_TYPE = "ONLINE_USER_TYPE_";/*** 在线用户数*/public static final String ONLINE_COUNT_KEY = "ONLINE_COUNT_KEY";
}

四、功能验证

打开WebSocket客户端，连接到ws://127.0.0.1:9095/demo/1

从截图来看，WebSocket服务端能正常接受并处理来自客户端的请求，验证成功！