1：pom导入依赖
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-websocket</artifactId>
<version>2.2.7.RELEASE</version>
</dependency>
2：myWebSocketClient自定义webSocket客户端
package com.example.poi.utils;
import org.springframework.stereotype.Component;
import javax.websocket.*;
import java.io.IOException;
@ClientEndpoint
@Component
public class MyWebSocketClient {
public Session session;
@OnOpen
public void onOpen(Session session) {
this.session = session;
System.out.println("WebSocket2连接已打开");
}
@OnMessage
public void onMessage(String message) {
System.out.println("收到消息2：" + message);
}
@OnClose
public void onClose() {
System.out.println("客户端关闭2");
}
@OnError
public void onError(Throwable throwable) {
System.err.println("发生错误2：" + throwable.getMessage());
}
public void sendMessage(String message) throws IOException {
session.getBasicRemote().sendText(message);
}
}
3：WebSocketServer自定义webSocket服务端
package com.example.poi.utils;
import cn.hutool.json.JSONObject;
import cn.hutool.log.Log;
import cn.hutool.log.LogFactory;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang.ObjectUtils;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;
import org.springframework.web.socket.server.standard.ServerEndpointExporter;
import javax.websocket.*;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;
import java.io.IOException;
import java.util.concurrent.CopyOnWriteArraySet;
@ServerEndpoint("/websocket/{sid}")
@Component
@Slf4j
public class WebSocketServer {
static Log log = LogFactory.get(WebSocketServer.class);
private static int onlineCount = 0;
private static CopyOnWriteArraySet<WebSocketServer> webSocketSet = new CopyOnWriteArraySet<WebSocketServer>();
public Session session;
private String sid = "";
@OnOpen
public void onOpen(Session session, @PathParam("sid") String sid) {
this.session = session;
webSocketSet.add(this);
addOnlineCount();
log.info("有新窗口开始监听:" + sid + ",当前在线人数为" + getOnlineCount());
this.sid = sid;
}
@OnClose
public void onClose() {
webSocketSet.remove(this);
subOnlineCount();
log.info("有一连接关闭！当前在线人数为" + getOnlineCount());
}
@OnMessage
public void onMessage(String message, Session session) {
log.info("收到来自窗口" + sid + "的信息:" + message);
for (WebSocketServer item : webSocketSet) {
if (ObjectUtils.equals(item.sid, sid)) {
try {
JSONObject jsonObject = new JSONObject();
jsonObject.put("name", sid);
item.sendMessage(jsonObject.toString());
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
@OnError
public void onError(Session session, Throwable error) {
log.error("发生错误");
error.printStackTrace();
}
public void sendMessage(String message) throws IOException {
this.session.getBasicRemote().sendText(message);
}
public CopyOnWriteArraySet<WebSocketServer> getWebSocketServer() {
return webSocketSet;
}
public String getSid(){
return sid;
}
public void close2(String ss){
for (WebSocketServer webSocketServer : webSocketSet) {
if (webSocketServer.sid.equals(ss)) {
webSocketSet.remove(webSocketServer);
log.info("删除了："+ss);
}
}
subOnlineCount();
log.info("有一连接关闭！当前在线人数为" + getOnlineCount());
}
public static void sendInfo(String message, @PathParam("sid") String sid) throws IOException {
log.info("推送消息到窗口" + sid + "，推送内容:" + message);
for (WebSocketServer item : webSocketSet) {
try {
if (sid == null) {
item.sendMessage(message);
} else if (item.sid.equals(sid)) {
item.sendMessage(message);
}
} catch (IOException e) {
continue;
}
}
}
public static synchronized int getOnlineCount() {
return onlineCount;
}
public static synchronized void addOnlineCount() {
WebSocketServer.onlineCount++;
}
public static synchronized void subOnlineCount() {
WebSocketServer.onlineCount--;
}
@Bean
public ServerEndpointExporter serverEndpointExporter() {
return new ServerEndpointExporter();
}
}
4：controller控制层
@SneakyThrows
@GetMapping("/testSql")
public List<EntityDemo> testSql(String id) {
try {
Random random = new Random();
Integer i = random.nextInt(5) + 1;
CopyOnWriteArraySet<WebSocketServer> webSocketServerSet = webSocketServer.getWebSocketServer();
for (WebSocketServer socketServer : webSocketServerSet) {
if (socketServer.getSid().equals(i.toString())) {
webSocketServer.close2(i.toString());
return null;
}
}
URI uri = new URI("ws://127.0.0.1:9088/test/websocket/" + i);
WebSocketContainer container = ContainerProvider.getWebSocketContainer();
container.connectToServer(myWebSocketClient, uri);
myWebSocketClient.sendMessage("你好" + i);
} catch (Exception e) {
throw new RuntimeException(e);
}
log.info("++++++");
return null;
}
5：注意事项：连接自动断开
- webSocket连接之后，发现一个问题：就是每隔一段时间如果不传送数据的话，与前端的连接就会自动断开。采用心跳消息的方式，就可以解决这个问题。比如客服端每隔30秒自动发送ping消息给服务端，服务端返回pong
5-1：注意事项：对象无法自动注入
- 使用了@ServerEndpoint注解的类中使用@Resource或@Autowired注入对象都会失败，并且报空指针异常，解决方法：如下
- @ServerEndpoint注解的类，使用静态对象，并且对外暴露set方法，这样在对象初始化的时候，将其注入到WebSocketServer
@ServerEndpoint("/websocket/{sid}")
@Component
@Slf4j
public class WebSocketServer {
private static EntityDemoServiceImpl entityDemoService;
public static void setEntityDemoService(EntityDemoServiceImpl entityDemoService) {
WebSocketServer.entityDemoService = entityDemoService;
}
- 在要注入到@ServerEndpoint注解的类中，使用@PostConstruct后置注入
@Service
public class EntityDemoServiceImpl extends ServiceImpl<EntityDemoMapper, EntityDemo> implements IEntityDemoService {
@PostConstruct
public void init() {
WebSocketServer.setEntityDemoService(this);
}
}
5-2：注意事项：Session无法被序列化
- 分布式场景会存在这样一个问题，当一次请求负载到第一台服务器时，session在第一台服务器线程上，第二次请求，负载到第二台服务器上，此时通过userId查找当前用户的session时，是查找不到的。
本来想着把session存入到redis中，就可以从redis获取用户的session，希望用这种方式来解决分布式场景下消息发送的问题。这种场景可以通过发送消息中间件的方式解决。具体这样解决：每次连接时，都将userId和对应的session存入到本机，发送消息时，直接发送给MQ-Broker，然后每台应用负载都去消费这个消息，拿到消息之后，判断在本机能根据userId是否能找到session，找到则推送到客户端
