前言
服务端一般都是被动接收请求，不主动向客户端发送信息。在某些场景情况下，客户需要及时获取更新的数据，有两种方法解决，一是由前端轮询定时调用接口，二是采用websocket服务端与客户端保持实时通信。
集成说明
采用tomcat自带的websocket实现，其中内置tomcat和外置tomcat集成稍有差别，外置tomcat不需要注入ServerEndpointExporter，因为它由容器自己提供和管理，websocket接收类不需要加@Component注解。如果涉及用户权限的问题，需要定义websocket拦截器，本文不再赘述。
集成步骤
1、pom.xml引入依赖
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| <dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-websocket</artifactId>
</dependency>
|
2、定义配置类注入ServerEndpointExporter
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| @Configuration
public class WebSocketConfig {
@Bean
public ServerEndpointExporter serverEndpointExporter() {
return new ServerEndpointExporter();
}
}
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3、定义websocket接收类
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| @ServerEndpoint("/websocket/{uuid}")
public class WebSocketServer {
private WebSocketService webSocketService = SpringUtil.getBean(WebSocketService.class);
private static final Logger log = LoggerFactory.getLogger(WebSocketServer.class);
private static int onlineCount = 0;
private static ConcurrentHashMap<String, Session> webSocketMap = new ConcurrentHashMap<>();
@OnOpen
public void onOpen(Session session, @PathParam("uuid") String uuid) throws InterruptedException {
if (webSocketMap.containsKey(uuid)) {
webSocketMap.remove(uuid);
webSocketMap.put(uuid, session);
} else {
webSocketMap.put(uuid, session);
addOnlineCount();
}
log.info("用户连接:{},当前在线人数为:{}", uuid, getOnlineCount());
sendMessageToSingle(WebSocketResult.success("connect", "连接成功"), uuid);
webSocketService.sendAllData(uuid);
}
@OnClose
public void onClose(@PathParam("uuid") String uuid) {
if (webSocketMap.containsKey(uuid)) {
webSocketMap.remove(uuid);
subOnlineCount();
}
log.info("用户退出:{},当前在线人数为:{}", uuid, getOnlineCount());
}
@OnMessage
public void onMessage(String message, Session session, @PathParam("uuid") String uuid) {
log.info("用户:{},发送消息:{}", uuid, message);
if (StringUtils.isNotBlank(message)) {
try {
} catch (Exception e) {
log.error(e.getMessage(), e);
}
}
}
@OnError
public void onError(Session session, Throwable error, @PathParam("uuid") String uuid) {
log.info("用户:{}连接错误,错误原因{}", uuid, error.getMessage());
if(webSocketMap.containsKey(uuid)){
webSocketMap.remove(uuid);
subOnlineCount();
}
}
public static void sendMessageToSingle(WebSocketResult message, String uuid) {
if (webSocketMap.containsKey(uuid)) {
try {
webSocketMap.get(uuid).getBasicRemote().sendText(JSON.toJSONString(message));
} catch (IOException e) {
log.error("发送消息异常:{}", e.getMessage());
}
} else {
log.error("用户:{}不在线", uuid);
}
}
public static void sendMessageToAll(WebSocketResult message) {
for (Map.Entry<String, Session> map : webSocketMap.entrySet()) {
sendMessageToSingle(message, map.getKey());
}
}
public static synchronized int getOnlineCount() {
return onlineCount;
}
public static synchronized void addOnlineCount() {
WebSocketServer.onlineCount++;
}
public static synchronized void subOnlineCount() {
WebSocketServer.onlineCount--;
}
}
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4、定义SpringUtil工具类，用于获取bean，因为WebSocketServer是多例对象，不能通过直接使用@Autowired注入bean
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| @Component
public class SpringUtil implements ApplicationContextAware {
private static ApplicationContext applicationContext;
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
SpringUtil.applicationContext = applicationContext;
}
public ApplicationContext getApplicationContext(){
return applicationContext;
}
public static Object getBean(String beanName){
return applicationContext.getBean(beanName);
}
public static <T> T getBean(Class<T> clazz){
return (T)applicationContext.getBean(clazz);
}
}
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5、定义WebSocketResult结果集，转换成json返回给前端
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| @Data
@NoArgsConstructor
@AllArgsConstructor
public class WebSocketResult implements Serializable {
private int code;
private String type;
private Object data;
public static WebSocketResult success(String type, Object data) {
return new WebSocketResult(200, type, data);
}
public static WebSocketResult fail(String type, Object data) {
return new WebSocketResult(500, type, data);
}
}
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格式为
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| {
"code": 200,
"data": {
"org_id": "30004",
"uuid": "1ebf7693-dc68-4093-aa6f-3fe31260e3fd"
},
"type": "KbsActualData"
}
|
code为状态码，data为数据，type为类型标识
