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這篇“Java應(yīng)用層協(xié)議WebSocket如何實(shí)現(xiàn)消息推送”文章的知識(shí)點(diǎn)大部分人都不太理解,所以小編給大家總結(jié)了以下內(nèi)容,內(nèi)容詳細(xì),步驟清晰,具有一定的借鑒價(jià)值,希望大家閱讀完這篇文章能有所收獲,下面我們一起來看看這篇“Java應(yīng)用層協(xié)議WebSocket如何實(shí)現(xiàn)消息推送”文章吧。
大部分的web開發(fā)者,開發(fā)的業(yè)務(wù)都是基于Http協(xié)議的:前端請(qǐng)求后端接口,攜帶參數(shù),后端執(zhí)行業(yè)務(wù)代碼,再返回結(jié)果給前端。作者參與開發(fā)的項(xiàng)目,有一個(gè)報(bào)警推送的功能,服務(wù)端實(shí)時(shí)推送報(bào)警信息給瀏覽器端;還有像抖音里面,如果有人關(guān)注、回復(fù)你的評(píng)論時(shí),抖音就會(huì)推送相關(guān)消息給你了,你就會(huì)收到一條消息。
有些同學(xué)會(huì)說了,基于Http協(xié)議也能實(shí)現(xiàn)?。呵岸硕〞r(shí)訪問后端(每隔3s或者幾秒),后端返回消息數(shù)據(jù),前端拿到后彈出消息。這種方式太low了,而且每個(gè)瀏覽器都這樣,使用系統(tǒng)的人一多,服務(wù)器的壓力就太大了些。那到底用什么技術(shù)手段實(shí)現(xiàn)呢?我們的主角就登場(chǎng)了。
WebSocket是在單個(gè)TCP連接上進(jìn)行全雙工通信的應(yīng)用層協(xié)議(Http協(xié)議也是應(yīng)用層),瀏覽器端和服務(wù)端都可主動(dòng)發(fā)送數(shù)據(jù)給另一端。這樣是不是比Http協(xié)議更適合消息推送這種場(chǎng)景。
建一個(gè)SpringBoot項(xiàng)目,Html放在src\main\resources\static下:
<!DOCTYPE html> <html lang="zh" xmlns:th="http://www.thymeleaf.org"> <head> <!-- 解決中文亂碼--> <meta charset="UTF-8"/> <title></title> <script type="text/javascript" src="./js/jquery.min.js"></script> </head> <body> <input id="input1" type="text" /><br/> <input type="button" value="瀏覽器發(fā)送服務(wù)端" onclick="btnClick()" /> <input type="button" value="服務(wù)端發(fā)送瀏覽器" onclick="btnClick1()" /> <input type="button" value="重新打開連接" onclick="btnClick2()" /> <br/> <textarea id="textArea" ></textarea> <script> var ws; webSocketInit(); function webSocketInit() { ws =new WebSocket('ws://localhost:8080/bootdemo/webSocket/10086'); // 獲取連接狀態(tài) console.log('ws連接狀態(tài)[初始]:' + ws.readyState); //監(jiān)聽是否連接成功 ws.onopen = function () { console.log('ws連接狀態(tài)[成功]:' + ws.readyState); }; // 接聽服務(wù)器發(fā)回的信息并處理展示 ws.onmessage = function (obj) { console.log('接收到來自服務(wù)器的消息:'); var txt = $("#textArea").val(); $("#textArea").val(txt + "\n" + obj.data); $("#textArea").scrollTop($("#textArea")[0].scrollHeight); //完成通信后關(guān)閉WebSocket連接 // ws.close(); }; // 監(jiān)聽連接關(guān)閉事件 ws.onclose = function () { // 監(jiān)聽整個(gè)過程中websocket的狀態(tài) console.log('ws連接狀態(tài)[關(guān)閉]:' + ws.readyState); }; // 監(jiān)聽并處理error事件 ws.onerror = function (error) { console.log(error); }; } function btnClick() { console.log("瀏覽器端發(fā)送消息:"); //連接成功則發(fā)送一個(gè)數(shù)據(jù) ws.send($("#input1").val()); } function btnClick1() { $.ajax({ url: 'http://localhost:8080/bootdemo/pushWebSocket/publish?' + 'userId=10086&message=' + $("#input1").val(), type: 'GET', success: function (data) { // console.log(data); } }); } function btnClick2() { webSocketInit(); } </script> </body> </html>
先引入依賴:
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-thymeleaf</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-websocket</artifactId> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <scope>provided</scope> </dependency>
bean上添加@ServerEndpoint,作為WebSocket的服務(wù)端。
import lombok.extern.slf4j.Slf4j; import org.springframework.stereotype.Component; import javax.websocket.OnMessage; import javax.websocket.OnOpen; import javax.websocket.Session; import javax.websocket.server.PathParam; import javax.websocket.server.ServerEndpoint; import java.util.HashMap; import java.util.Map; import java.util.concurrent.CopyOnWriteArraySet; @Component @Slf4j @ServerEndpoint("/webSocket/{userId}") public class WebSocketServer { //與某個(gè)客戶端的連接會(huì)話,需要通過它來給客戶端發(fā)送數(shù)據(jù) private Session session; private static final CopyOnWriteArraySet<WebSocketServer> webSockets = new CopyOnWriteArraySet<>(); // 用來存在線連接數(shù) private static final Map<String, Session> sessionPool = new HashMap<String, Session>(); /** * 連接成功調(diào)用的方法 */ @OnOpen public void onOpen(Session session, @PathParam(value = "userId") String userId) { try { this.session = session; webSockets.add(this); sessionPool.put(userId, session); } catch (Exception e) { } } /** * 收到客戶端消息后調(diào)用的方法 */ @OnMessage public void onMessage(String message) { log.info("websocket消息: 收到客戶端消息:" + message); } public void sendOneMessage(String userId, String message) { Session session = sessionPool.get(userId); if (session != null && session.isOpen()) { try { log.info("服務(wù)端推送消息:" + message); session.getAsyncRemote().sendText(message); } catch (Exception e) { e.printStackTrace(); } } } }
進(jìn)行注冊(cè):
@Configuration public class WebSocketConfigOne { /** * 這個(gè)bean會(huì)自動(dòng)注冊(cè)使用了@ServerEndpoint注解聲明的對(duì)象 * 沒有的話會(huì)報(bào)404 * * @return */ @Bean public ServerEndpointExporter serverEndpointExporter() { return new ServerEndpointExporter(); } }
推送消息的控制器:
import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.ResponseBody; import java.util.HashMap; import java.util.Map; @Controller @RequestMapping("/pushWebSocket") public class WebSocketController { @Autowired private WebSocketServer webSocketServer; @GetMapping("/publish") @ResponseBody public Map publish(String userId, String message) { webSocketServer.sendOneMessage(userId, message); HashMap<String, Object> map = new HashMap<>(); map.put("code", 200); return map; } }
還有我的配置文件application.properties:
# web port
server.port=8080
server.servlet.context-path=/bootdemo
運(yùn)行啟動(dòng)類后,訪問html(localhost:8080/bootdemo/index.html)如下:
有的同學(xué)一思索,點(diǎn)擊圖中的第2個(gè)按鈕"服務(wù)端發(fā)送瀏覽器",你這好像也是前端先請(qǐng)求,再推送的消息;我們的WebSocketController#publish方法,在真實(shí)的場(chǎng)景下,可以在后端的定時(shí)任務(wù)中、消息中間件的消費(fèi)者端調(diào)用,不用前端先發(fā)送請(qǐng)求。
當(dāng)然SpringBoot有專門構(gòu)建WebSocket服務(wù)端的方式。
核心配置類:
import lombok.extern.slf4j.Slf4j; import org.springframework.context.annotation.Configuration; import org.springframework.http.server.ServerHttpRequest; import org.springframework.http.server.ServerHttpResponse; import org.springframework.http.server.ServletServerHttpRequest; import org.springframework.web.servlet.HandlerMapping; import org.springframework.web.socket.WebSocketHandler; import org.springframework.web.socket.config.annotation.EnableWebSocket; import org.springframework.web.socket.config.annotation.WebSocketConfigurer; import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry; import org.springframework.web.socket.server.HandshakeInterceptor; import javax.servlet.http.HttpServletRequest; import java.util.Map; @Configuration @EnableWebSocket @Slf4j public class WebSocketConfig1 implements WebSocketConfigurer { @Override public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) { registry.addHandler(new MyWebSocketHandler(), "/webSocket/{userId}")//設(shè)置連接路徑和處理 .setAllowedOrigins("*") .addInterceptors(new MyWebSocketInterceptor());//設(shè)置攔截器 } class MyWebSocketInterceptor implements HandshakeInterceptor { //前置攔截一般用來注冊(cè)用戶信息,綁定 WebSocketSession @Override public boolean beforeHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, Map<String, Object> attributes) throws Exception { log.info("前置攔截~~"); if (!(request instanceof ServletServerHttpRequest)) { return true; } HttpServletRequest servletRequest = ((ServletServerHttpRequest)request).getServletRequest(); Map map = (Map)servletRequest.getAttribute(HandlerMapping. URI_TEMPLATE_VARIABLES_ATTRIBUTE); String userId = (String)map.get("userId"); attributes.put("userId", userId); return true; } @Override public void afterHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, Exception exception) { log.info("后置攔截~~"); } } }
核心處理器:
import lombok.extern.slf4j.Slf4j; import org.springframework.stereotype.Component; import org.springframework.web.socket.*; import java.util.Map; import java.util.concurrent.ConcurrentHashMap; @Slf4j @Component public class MyWebSocketHandler implements WebSocketHandler { private static final Map<String, WebSocketSession> SESSIONS = new ConcurrentHashMap<>(); /** * 建立新的socket連接后回調(diào)的方法 */ @Override public void afterConnectionEstablished(WebSocketSession session) throws Exception { String userId = (String) session.getAttributes().get("userId"); SESSIONS.put(userId, session); } /** * 接收到瀏覽器端的消息后回調(diào)的方法 */ @Override public void handleMessage(WebSocketSession session, WebSocketMessage<?> message) throws Exception { String msg = message.getPayload().toString(); log.info("收到客戶端消息:" + msg); } /** * 連接出錯(cuò)時(shí)回調(diào)的方法 */ @Override public void handleTransportError(WebSocketSession session, Throwable exception) throws Exception { log.info("連接出錯(cuò)"); if (session.isOpen()) { session.close(); } } /** * 連接關(guān)閉時(shí)回調(diào)的方法 */ @Override public void afterConnectionClosed(WebSocketSession session, CloseStatus closeStatus) throws Exception { log.info("連接關(guān)閉:status:" + closeStatus); } /** * 是否處理部分消息,返回false就行 */ @Override public boolean supportsPartialMessages() { return false; } /** * 推送消息給瀏覽器端 */ public void sendMessage(String userId, String message) { WebSocketSession webSocketSession = SESSIONS.get(userId); if (webSocketSession == null || !webSocketSession.isOpen()) { return; } try { webSocketSession.sendMessage(new TextMessage(message)); } catch (Exception ex) { log.error("推送消息異常:" + ex); } } }
控制器也改造下:
import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.ResponseBody; import java.util.HashMap; import java.util.Map; @Controller @RequestMapping("/pushWebSocket") public class WebSocketController { @Autowired private MyWebSocketHandler handler; @GetMapping("/publish") @ResponseBody public Map publish(String userId, String message) { handler.sendMessage(userId, message); HashMap<String, Object> map = new HashMap<>(); map.put("code", 200); return map; } }
前端部分不用做修改,和之前一樣的代碼。
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