Spring Boot整合WebSocket实现实时消息推送
0. 开发环境
- JDK：1.8
- Spring Boot：2.1.1.RELEASE
1. 引入依赖
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-websocketartifactId>
dependency>
2. 新建WebSocket配置类
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.socket.server.standard.ServerEndpointExporter;
@Configuration
public class WebSocketConfig {
/**
* ServerEndpointExporter注入
* 该Bean会自动注册使用@ServerEndpoint注解申明的WebSocket endpoint
*
* @return
*/
@Bean
public ServerEndpointExporter serverEndpointExporter() {
return new ServerEndpointExporter();
}
}
3. 新建WebSocket服务类
package cn.wbnull.springbootdemo.service;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import javax.websocket.*;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;
import java.io.IOException;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
@Component
@ServerEndpoint("/websocket/{terminalId}")
public class WebSocketService {
private final Logger logger = LoggerFactory.getLogger(WebSocketService.class);
/**
* 保存连接信息
*/
private static final Map<String, Session> CLIENTS = new ConcurrentHashMap<>();
@OnOpen
public void onOpen(@PathParam("terminalId") String terminalId, Session session) throws Exception {
logger.info(session.getRequestURI().getPath() + "，打开连接开始：" + session.getId());
//当前连接已存在，关闭
if (CLIENTS.containsKey(terminalId)) {
onClose(CLIENTS.get(terminalId));
}
CLIENTS.put(terminalId, session);
logger.info(session.getRequestURI().getPath() + "，打开连接完成：" + session.getId());
}
@OnClose
public void onClose(@PathParam("terminalId") String terminalId, Session session) throws Exception {
logger.info(session.getRequestURI().getPath() + "，关闭连接开始：" + session.getId());
CLIENTS.remove(terminalId);
logger.info(session.getRequestURI().getPath() + "，关闭连接完成：" + session.getId());
}
@OnMessage
public void onMessage(String message, Session session) {
logger.info("前台发送消息：" + message);
}
@OnError
public void onError(Session session, Throwable error) {
logger.error(error.toString());
}
public void onClose(Session session) {
//判断当前连接是否在线
// if (!session.isOpen()) {
// return;
// }
try {
session.close();
} catch (IOException e) {
logger.error("金斗云关闭连接异常：" + e);
}
}
public void sendMessage(String message, Session session) {
try {
session.getAsyncRemote().sendText(message);
logger.info("推送成功：" + message);
} catch (Exception e) {
logger.error("推送异常：" + e);
}
}
public boolean sendMessage(String terminalId, String message) {
try {
Session session = CLIENTS.get(terminalId);
session.getAsyncRemote().sendText(message);
logger.info("推送成功：" + message);
return true;
} catch (Exception e) {
logger.error("推送异常：" + e);
return false;
}
}
}
4. 新建Web端连接页面
DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>WebSocket Testtitle>
head>
<body>
<label for="text">label><input id="text" type="text"/>
<button onclick="sendMessage()">发送消息button>
<button onclick="closeWebSocket()">关闭连接button>
<div id="message">div>
body>
<script type="text/javascript">
let websocket = null;
//判断当前浏览器是否支持WebSocket
if ('WebSocket' in window) {
websocket = new WebSocket("ws://localhost:8090/websocket/123456");
} else {
alert('Not support websocket');
}
//连接发生错误的回调方法
websocket.onerror = function () {
showMessage("打开连接失败");
};
//连接成功建立的回调方法
websocket.onopen = function (event) {
showMessage("打开连接成功");
}
//接收到消息的回调方法
websocket.onmessage = function (event) {
showMessage(event.data);
}
//连接关闭的回调方法
websocket.onclose = function () {
showMessage("关闭连接成功");
}
//监听窗口关闭事件，当窗口关闭时，主动关闭WebSocket连接
window.onbeforeunload = function () {
websocket.close();
}
function showMessage(message) {
document.getElementById('message').innerHTML += message + '
';
}
function closeWebSocket() {
websocket.close();
}
//发送消息
function sendMessage() {
const message = document.getElementById('text').value;
websocket.send(message);
}
script>
html>
5. 设置后端消息推送
为便于测试，直接修改WebSocketService，当收到前台消息时，直接给前台发送消息
@OnMessage
public void onMessage(String message, Session session) {
logger.info("前台发送消息：" + message);
sendMessage("收到消息：" + message, session);
}
6. 测试
浏览器访问http://127.0.0.1:8090/，页面显示如下：
后台日志如下：
2022-07-02 21:03:22.753 INFO 9168 --- [nio-8090-exec-2] c.w.s.service.WebSocketService : /websocket/123456，打开连接开始：0
2022-07-02 21:03:22.753 INFO 9168 --- [nio-8090-exec-2] c.w.s.service.WebSocketService : /websocket/123456，打开连接完成：0
当我们浏览器打开第二个页面，第一个页面会显示断开连接
后台日志如下：
2022-07-02 21:04:01.936 INFO 9168 --- [nio-8090-exec-4] c.w.s.service.WebSocketService : /websocket/123456，打开连接开始：1
2022-07-02 21:04:01.938 INFO 9168 --- [nio-8090-exec-4] c.w.s.service.WebSocketService : /websocket/123456，关闭连接开始：0
2022-07-02 21:04:01.938 INFO 9168 --- [nio-8090-exec-4] c.w.s.service.WebSocketService : /websocket/123456，关闭连接完成：0
2022-07-02 21:04:01.938 INFO 9168 --- [nio-8090-exec-4] c.w.s.service.WebSocketService : /websocket/123456，打开连接完成：1
前台页面录入消息并发送，后台可正常收到消息
2022-07-02 21:08:21.860 INFO 1772 --- [nio-8090-exec-3] c.w.s.service.WebSocketService : 前台发送消息：测试消息
2022-07-02 21:08:21.863 INFO 1772 --- [nio-8090-exec-3] c.w.s.service.WebSocketService : 推送成功：收到消息：测试消息
前台页面显示正常
点击关闭连接，可以正常关闭
7. 服务保活
对于实时消息推送相关服务，都存在保活问题。这里我们采用心跳保活。 修改WebSocketService类
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import javax.websocket.*;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;
@Component
@ServerEndpoint("/websocket/{terminalId}")
public class WebSocketService {
private final Logger logger = LoggerFactory.getLogger(WebSocketService.class);
/**
* 保存连接信息
*/
private static final Map<String, Session> CLIENTS = new ConcurrentHashMap<>();
private static final Map<String, AtomicInteger> TERMINAL_IDS = new HashMap<>();
@OnOpen
public void onOpen(@PathParam("terminalId") String terminalId, Session session) throws Exception {
logger.info(session.getRequestURI().getPath() + "，打开连接开始：" + session.getId());
//当前连接已存在，关闭
if (CLIENTS.containsKey(terminalId)) {
onClose(CLIENTS.get(terminalId));
}
TERMINAL_IDS.put(terminalId, new AtomicInteger(0));
CLIENTS.put(terminalId, session);
logger.info(session.getRequestURI().getPath() + "，打开连接完成：" + session.getId());
}
@OnClose
public void onClose(@PathParam("terminalId") String terminalId, Session session) throws Exception {
logger.info(session.getRequestURI().getPath() + "，关闭连接开始：" + session.getId());
CLIENTS.remove(terminalId);
TERMINAL_IDS.remove(terminalId);
logger.info(session.getRequestURI().getPath() + "，关闭连接完成：" + session.getId());
}
@OnMessage
public void onMessage(String message, Session session) {
logger.info("前台发送消息：" + message);
if ("心跳".equals(message)) {
//重置当前终端心跳次数
TERMINAL_IDS.get(message).set(0);
return;
}
sendMessage("收到消息：" + message, session);
}
@OnError
public void onError(Session session, Throwable error) {
logger.error(error.toString());
}
public void onClose(Session session) {
//判断当前连接是否在线
// if (!session.isOpen()) {
// return;
// }
try {
session.close();
} catch (IOException e) {
logger.error("金斗云关闭连接异常：" + e);
}
}
public void heartbeat() {
//检查所有终端心跳次数
for (String key : TERMINAL_IDS.keySet()) {
//心跳3次及以上的主动断开
if ((TERMINAL_IDS.get(key).intValue() >= 3)) {
logger.info("心跳超时，关闭连接：" + key);
onClose(CLIENTS.get(key));
}
}
for (String key : CLIENTS.keySet()) {
//记录当前终端心跳次数
TERMINAL_IDS.get(key).incrementAndGet();
sendMessage("心跳", CLIENTS.get(key));
}
}
public void sendMessage(String message, Session session) {
try {
session.getAsyncRemote().sendText(message);
logger.info("推送成功：" + message);
} catch (Exception e) {
logger.error("推送异常：" + e);
}
}
public boolean sendMessage(String terminalId, String message) {
try {
Session session = CLIENTS.get(terminalId);
session.getAsyncRemote().sendText(message);
logger.info("推送成功：" + message);
return true;
} catch (Exception e) {
logger.error("推送异常：" + e);
return false;
}
}
}
8. 新增定时任务
新增定时任务，定时给连接到WebSocket的终端发送消息，超过指定次数未回应的终端视为离线，主动关闭连接。
import cn.wbnull.springbootdemo.service.WebSocketService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;
@EnableScheduling
@Component
public class WebSocketScheduled {
@Autowired
private WebSocketService webSocketService;
@Scheduled(cron = "0/15 * * * * ?")
public void heartbeat() {
webSocketService.heartbeat();
}
}
同样的，前台也需要定时心跳WebSocket，这里不做赘述。
9. Bean注入
WebSocket服务类中，使用@Autowired直接注入Service或普通Bean时，会报空指针错误。这是因为Spring管理对象时使用单例模式，但WebSocket服务为多对象。
Spring Boot项目在启动初始化时，会初始化非用户连接的WebSocket服务，为其注入Service，此时使用@Autowired注入的Service不为null，即被成功注入。 但，Spring默认管理的是单例，所以只会注入一次Service。 当新用户连接时，系统又会创建一个新的WebSocket对象，Spring就不会给第二个 WebSocket对象注入Service了，所以导致只要是用户连接创建的WebSocket 对象，都不能再注入了。
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import javax.websocket.*;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;
@Component
@ServerEndpoint("/websocket/{terminalId}")
public class WebSocketService {
//code
/**
* 需要注入的Service声明为静态，让其属于类
*/
private static TerminalService terminalService;
/**
* 注入的时候，给类的Service注入
*/
@Autowired
public void setMchDeviceInfoService(TerminalService terminalService) {
WebSocketService.terminalService = terminalService;
}
@OnOpen
public void onOpen(@PathParam("terminalId") String terminalId, Session session) throws Exception {
//code
terminalService.terminal();
}
//code
}
测试日志打印如下
2022-07-02 21:26:08.166 INFO 9924 --- [nio-8090-exec-2] c.w.s.service.WebSocketService : /websocket/123456，打开连接开始：0
2022-07-02 21:26:08.166 INFO 9924 --- [nio-8090-exec-2] c.w.s.service.WebSocketService : /websocket/123456，打开连接完成：0
2022-07-02 21:26:08.166 INFO 9924 --- [nio-8090-exec-2] c.w.s.service.TerminalService : 这是一条测试日志