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详细解析WebSocket+spring示例demo(已使用sockJs库)

时间:2022-11-14 22:03:02 编辑:袖梨 来源:一聚教程网

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1、简介

作为下一代的Web标准,HTML5拥有许多引人注目的新特性,如 Canvas、本地存储、多媒体编程接口、WebSocket等等。这其中有“Web的 TCP”之称的 WebSocket格外吸引开发人员的注意。WebSocket的出现使得浏览器提供对 Socket的支持成为可能,从而在浏览器和服务器之间提供了一个基于TCP连接的双向通道。Web开发人员可以非常方便地使用WebSocket构建实时 web 应用,开发人员的手中从此又多了一柄神兵利器。

Web 应用的信息交互过程通常是客户端通过浏览器发出一个请求,服务器端接收和审核完请求后进行处理并返回结果给客户端,然后客户端浏览器将信息呈现出来,这种机制对于信息变化不是特别频繁的应用尚能相安无事,但是对于那些实时要求比较高的应用来说,比如说在线游戏、在线证券、设备监控、新闻在线播报、RSS订阅推送等等,当客户端浏览器准备呈现这些信息的时候,这些信息在服务器端可能已经过时了。

所以保持客户端和服务器端的信息同步是实时 Web应用的关键要素,对 Web开发人员来说也是一个难题。在 WebSocket规范出来之前,开发人员想实现这些实时的Web应用,不得不采用一些折衷的方案,其中最常用的就是轮询(Polling)和 Comet 技术,而Comet技术实际上是轮询技术的改进,又可细分为两种实现方式,一种是长轮询机制,一种称为流技术。

Html5 WebSocket 设计出来的目的就是要取代轮询和 Comet技术,使客户端浏览器具备像 C/S架构下桌面系统的实时通讯能力。浏览器通过JavaScript向服务器发出建立 WebSocket连接的请求,连接建立以后,客户端和服务器端就可以通过 TCP连接直接交换数据。因为 WebSocket连接本质上就是一个TCP连接,所以在数据传输的稳定性和数据传输量的大小方面,和轮询以及Comet技术比较,具有很大的性能优势。

但是鉴于web socket 对浏览器要求比较高,为了解决这个问题,推出了sockJS,SockJS是一个JavaScript库,提供跨浏览器javascript的API,创建了一个低延迟、全双工的浏览器和web服务器之间通信通道。

2、相关环境要求

Spring4.0.6(要选择4.0+),tomcat7.0.55版本,JDK1.7。

3、具体代码

(以下代码亲测可用!)

(1)web.xml:

代码如下 复制代码

xmlns="http://xmlns.j***cp.org/xml/ns/javaee"

xmlns:xsi="http://www.**w*3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://xmlns.j***cp.org/xml/ns/javaee http://xmlns.j***cp.org/xml/ns/javaee/web-app_3_1.xsd">

用来测试WebSocket基础上推送的功能

encodingFilter

org.springframework.web.filter.CharacterEncodingFilter

true

encoding

UTF-8

forceEncoding

true

encodingFilter

/*

org.springframework.web.context.ContextLoaderListener

org.springframework.web.util.IntrospectorCleanupListener

dispatcher

org.springframework.web.servlet.DispatcherServlet

contextConfigLocation

classpath:dispatcher-servlet.xml

1

true

dispatcher

/

30

testSocket.jsp

(2) dispatcher-servlet.xml

代码如下 复制代码

xmlns:xsi="http://www.**w*3.org/2001/XMLSchema-instance"

xmlns:beans="http://www.spring*fram*ewo*rk.org/schema/beans"

xmlns:context="http://www.spr*i*ngframewo*rk.org/schema/context"

xsi:schemaLocation="http://www.spri**ngfra*mework.org/schema/mvc http://www.spri**ngfra*mework.org/schema/mvc/spring-mvc.xsd

http://www.spring*fram*ewo*rk.org/schema/beans http://www.spring*fram*ewo*rk.org/schema/beans/spring-beans.xsd

http://www.spr*i*ngframewo*rk.org/schema/context http://www.spr*i*ngframewo*rk.org/schema/context/spring-context.xsd">

(3)HandshakeInterceptor.java

代码如下 复制代码

packagezyy.sockjs.config;

importjava.util.Map;

importorg.springframework.http.server.ServerHttpRequest;

importorg.springframework.http.server.ServerHttpResponse;

importorg.springframework.stereotype.Component;

importorg.springframework.web.socket.WebSocketHandler;

importorg.springframework.web.socket.server.support.HttpSessionHandshakeInterceptor;

@Component

publicclassHandshakeInterceptorextendsHttpSessionHandshakeInterceptor {

@Override

publicbooleanbeforeHandshake(ServerHttpRequest request,

ServerHttpResponse response, WebSocketHandler wsHandler,

Map attributes)throwsException {

System.out.println("Before Handshake");

returnsuper.beforeHandshake(request,response,wsHandler,attributes);

}

@Override

publicvoidafterHandshake(ServerHttpRequest request,

ServerHttpResponse response, WebSocketHandler wsHandler,

Exception ex) {

System.out.println("After Handshake");

super.afterHandshake(request,response,wsHandler,ex);

}

}

(4)InfoSocketEndPoint.Java

代码如下 复制代码

packagezyy.sockjs.config;

importorg.springframework.stereotype.Component;

importorg.springframework.web.socket.TextMessage;

importorg.springframework.web.socket.WebSocketSession;

importorg.springframework.web.socket.handler.TextWebSocketHandler;

@Component

publicclassInfoSocketEndPointextendsTextWebSocketHandler {

publicInfoSocketEndPoint() {

}

@Override

protectedvoidhandleTextMessage(WebSocketSession session,

TextMessage message)throwsException {

super.handleTextMessage(session, message);

TextMessage returnMessage =newTextMessage(message.getPayload()

+" received at server");

session.sendMessage(returnMessage);

}

}

(5)SystemWebSocketHandler.java

代码如下 复制代码

packagezyy.sockjs.config;

importorg.springframework.stereotype.Component;

importorg.springframework.web.socket.CloseStatus;

importorg.springframework.web.socket.TextMessage;

importorg.springframework.web.socket.WebSocketHandler;

importorg.springframework.web.socket.WebSocketMessage;

importorg.springframework.web.socket.WebSocketSession;

/**

*

* @author dayu

*/

@Component

publicclassSystemWebSocketHandlerimplementsWebSocketHandler {

@Override

publicvoidafterConnectionEstablished(WebSocketSession session)throwsException {

System.out.println("connect to the websocket success......");

session.sendMessage(newTextMessage("Server:connected OK!"));

}

@Override

publicvoidhandleMessage(WebSocketSession wss, WebSocketMessage> wsm)throwsException {

TextMessage returnMessage =newTextMessage(wsm.getPayload()

+" received at server");

wss.sendMessage(returnMessage);

}

@Override

publicvoidhandleTransportError(WebSocketSession wss, Throwable thrwbl)throwsException {

if(wss.isOpen()){

wss.close();

}

System.out.println("websocket connection closed......");

}

@Override

publicvoidafterConnectionClosed(WebSocketSession wss, CloseStatus cs)throwsException {

System.out.println("websocket connection closed......");

}

@Override

publicbooleansupportsPartialMessages() {

returnfalse;

}

}

(6)WebSocketConfig.java

代码如下 复制代码

packagezyy.sockjs.config;

importorg.springframework.context.annotation.Bean;

importorg.springframework.context.annotation.Configuration;

importorg.springframework.web.servlet.config.annotation.EnableWebMvc;

importorg.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

importorg.springframework.web.socket.WebSocketHandler;

importorg.springframework.web.socket.config.annotation.EnableWebSocket;

importorg.springframework.web.socket.config.annotation.WebSocketConfigurer;

importorg.springframework.web.socket.config.annotation.WebSocketHandlerRegistry;

@Configuration

@EnableWebMvc

@EnableWebSocket

publicclassWebSocketConfigextendsWebMvcConfigurerAdapterimplements

WebSocketConfigurer {

publicWebSocketConfig() {

}

@Override

publicvoidregisterWebSocketHandlers(WebSocketHandlerRegistry registry) {

registry.addHandler(systemWebSocketHandler(),"/websck").addInterceptors(newHandshakeInterceptor());

System.out.println("registed!");

registry.addHandler(systemWebSocketHandler(),"/sockjs/websck/info").addInterceptors(newHandshakeInterceptor())

.withSockJS();

}

@Bean

publicWebSocketHandler systemWebSocketHandler() {

returnnewSystemWebSocketHandler();

}

}

(7)testSocket.jsp

代码如下 复制代码

WebSocket/SockJS Echo Sample (Adapted from Tomcat's echo sample)

#connect-container {

float: left;

width: 400px

}

#connect-container div {

padding: 5px;

}

#console-container {

float: left;

margin-left: 15px;

width: 400px;

}

#console {

border:1px solid #CCCCCC;

border-right-color:#33333333;

border-bottom-color:#999999;

height: 170px;

overflow-y: scroll;

padding: 5px;

width: 100%;

}

#console p {

padding: 0;

margin: 0;

}

var ws = null;

var url = null;

var transports = [];

function setConnected(connected) {

document.getElementById('connect').disabled = connected;

document.getElementById('disconnect').disabled = !connected;

document.getElementById('echo').disabled = !connected;

}

function connect() {

if (!url) {

log('Select whether to use W3C WebSocket or SockJS');

return;

}

//ws = (url.indexOf('sockjs') != -1) ?new SockJS(url, undefined, {protocols_whitelist: transports}) : new WebSocket(url);

if ('WebSocket'in window) {

ws= new WebSocket("ws://localhost:8080/SpringSocketJs/websck");

}else {

ws = new SockJS("http://*lo*calhost*:8080/SpringSocketJs/sockjs/websck/info");

}

//websocket = new SockJS("http://loc*alhost:**8084/SpringWebSocketPush/sockjs/websck");

ws.onopen = function () {

setConnected(true);

//log('Info: connection opened.');

};

ws.onmessage = function (event) {

log('Received:' + event.data);

};

ws.onclose = function (event) {

setConnected(false);

log('Info: connection closed.');

log(event);

};

}

function disconnect() {

if (ws != null) {

ws.close();

ws = null;

}

setConnected(false);

}

function echo() {

if (ws != null) {

var message = document.getElementById('message').value;

log('Sent:' + message);

ws.send(message);

} else {

alert('connection not established, please connect.');

}

}

function updateUrl(urlPath) {

if (urlPath.indexOf('sockjs') != -1) {

url = urlPath;

document.getElementById('sockJsTransportSelect').style.visibility ='visible';

}

else {

if (window.location.protocol =='http:') {

url = 'ws://' + window.location.host + urlPath;

}else{

url = 'wss://' + window.location.host + urlPath;

}

document.getElementById('sockJsTransportSelect').style.visibility ='hidden';

}

}

function updateTransport(transport) {

transports = (transport == 'all') ? [] : [transport];

}

function log(message) {

var console = document.getElementById('console');

var p = document.createElement('p');

p.style.wordWrap = 'break-word';

p.appendChild(document.createTextNode(message));

console.appendChild(p);

while (console.childNodes.length > 25) {

console.removeChild(console.firstChild);

}

console.scrollTop = console.scrollHeight;

}

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