WebSocket是两个应用之间全双工的通信通道。WebSocket最常见的应用场景是实现服务器和基于浏览器的应用之间的通信。
浏览器中的javascript客户端开启一个到服务器的连接，服务器通过这个连接发送更新给浏览器。相比轮询服务端以查找更新的
方案，这种技术更加高效。
下面将通过两种方式（XML配置和Java类配置）实现WebSocket的简单应用。
需要说明的是，由于本人浏览器无法支持WebSocket（这也是WebSocket令人遗憾的地方），所以使用WebSocket的备用方案
SockJS。SockJS会优先选用WebSocket，但是如果WebSocket不可用的话，它将会从其他方案中挑选最优方案。
不论哪种方案，首先要在maven项目中添加相关依赖：
<!-- WebSocket依赖 -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-websocket</artifactId>
<version>5.1.3.RELEASE</version>
</dependency>
<!-- 处理json数据 -->
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.9.8</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.9.8</version>
</dependency>
注意，后两个依赖不能忘记，不然会在通信时出错
一、通过XML配置
在之前的项目中，我们首先创建example.websocket包，用于存放我们定义的处理器类。在该包中创建我们的
WebSocket处理器类MyHandler:
package example.websocket; import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.socket.CloseStatus;
import org.springframework.web.socket.TextMessage;
import org.springframework.web.socket.WebSocketSession;
import org.springframework.web.socket.handler.TextWebSocketHandler; /**
* webSocket处理器
*/
public class MyHandler extends TextWebSocketHandler {
private static final Logger log = LoggerFactory.getLogger(MyHandler.class); /**
* 处理接收的信息行为
* @param session
* @param message
* @throws Exception
*/
@Override
protected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception {
log.info("Received message: " + message.getPayload());
session.sendMessage(new TextMessage("Server has received your message"));
} /**
* 处理建立连接后的事件
* @param session
* @throws Exception
*/
@Override
public void afterConnectionEstablished(WebSocketSession session) throws Exception {
log.info("Connection established");
} /**
* 处理连接关闭事件
* @param session
* @param status
* @throws Exception
*/
@Override
public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {
log.info("Connection closed. Status: " + status);
}
}
接下来我们要在DispatcherServlet中配置我们的WebSocket：
<websocket:handlers>
<websocket:mapping path="/myHandler" handler="myHandler"/>
<websocket:sockjs/>
</websocket:handlers>
<bean id="myHandler" class="example.websocket.MyHandler"/>
注意，这段代码应放入dispatcher-servlet.xml中，其中<websocket:sockjs/>标签配置了SockJS
接下来我们创建一个新的Controller类用于加载一个独立的视图：
package example.controller; import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView; @Controller
@RequestMapping(value = "websocket")
public class CommunicationController { @RequestMapping(method = RequestMethod.GET)
public ModelAndView webSocketView() {
ModelAndView modelAndView = new ModelAndView("webSocketClient");
return modelAndView;
}
}
下面我们来编写一个简易的前端代码，创建webSocketClient.jsp文件，需要注意，在使用SockJS之前，需要引入相应的库，
具体参见https://github.com/sockjs/sockjs-client，这里借用了其他博主的代码https://blog.csdn.net/dadiyang/article/details/83715569
<%--
Created by IntelliJ IDEA.
User: asus1
Date: 2019/1/24
Time: 21:58
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>webSocket客户端</title>
</head>
<body>
<h1>Welcome!</h1>
<ul id="ul">
</ul>
<script type="text/javascript" src="${pageContext.request.contextPath}/statics/js/sockjs-1.0.0.min.js"></script>
<script>
var url = '/myHandler';
var sock = new SockJS(url); sock.onopen = function (ev) {
console.log("opening");
sayHey();
};
sock.onmessage = function (ev) {
console.log(ev.data);
var li = document.createElement("li");
li.innerText = ev.data;
document.getElementById("ul").appendChild(li);
setTimeout(sayHey, 2000);
};
sock.onclose = function (ev) {
console.log("closed");
};
function sayHey() {
console.log("sending 'Hey guy!'");
sock.send("Hey guy!");
};
</script>
</body>
</html>
运行项目结果：
二、通过java类配置
完全依照其他博主的方法重新创建了一个项目，整个项目通过java类进行配置
参考资料：https://blog.csdn.net/dadiyang/article/details/83715569
《Spring 实战（第4版）》
下面直接粘代码：
配置类：
RootConfig:
package com.example.config; import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.FilterType;
import org.springframework.web.servlet.config.annotation.EnableWebMvc; @Configuration
@ComponentScan(basePackages = {"com.example"},
excludeFilters = {
@ComponentScan.Filter(type = FilterType.ANNOTATION, value = EnableWebMvc.class)
})
public class RootConfig {
}
WebConfig:
package com.example.config; import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.ViewResolverRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import org.springframework.web.servlet.view.InternalResourceViewResolver; /**
* WebMvcConfigurerAdapter在新版本中已被弃用
* 可以通过实现WebMvcConfigurer或者拓展WebMvcConfigurerSupport
* 替代WebMvcConfigurerAdapter的拓展
*/
@Configuration
@EnableWebMvc
@ComponentScan(basePackages = {"com.example"})
public class WebConfig implements WebMvcConfigurer { /**
* 配置jsp视图解析器
* @param registry
*/
@Override
public void configureViewResolvers(ViewResolverRegistry registry) {
registry.jsp("/WEB-INF/views/", ".jsp");
} /**
* 配置静态资源的处理
* @param configurer
*/
@Override
public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
configurer.enable();
}
}
WebSocketConfig:
package com.example.config; import com.example.websocket.MyHandler;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.socket.config.annotation.EnableWebSocket;
import org.springframework.web.socket.config.annotation.WebSocketConfigurer;
import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry; @Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {
@Override
public void registerWebSocketHandlers(WebSocketHandlerRegistry webSocketHandlerRegistry) {
webSocketHandlerRegistry.addHandler(myHandler(), "/myHandler").withSockJS();
} @Bean
public MyHandler myHandler() {
return new MyHandler();
}
}
WebApp初始化类：
package com.example.webappinit; import com.example.config.RootConfig;
import com.example.config.WebConfig;
import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer; public class wsWebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
@Override
protected Class<?>[] getRootConfigClasses() {
return new Class[] {RootConfig.class};
} @Override
protected String[] getServletMappings() {
return new String[] {"/"};
} @Override
protected Class<?>[] getServletConfigClasses() {
return new Class[] {WebConfig.class};
}
}
其他代码与XML配置一样
运行项目结果：