简介
WebSocket提供了在客户端和服务端通过单一TCP连接建立全双工双向通信的通道。它是和HTTP不同的TCP协议,但是却建立在HTTP之上,使用80,443端口并且允许重用防火墙规则。
WebSocket通过HTTP请求的Upgrade
头开启交互,如下:
GET /spring-websocket-portfolio/portfolio HTTP/1.1
Host: localhost:8080
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: Uc9l9TMkWGbHFD2qnFHltg==
Sec-WebSocket-Protocol: v10.stomp, v11.stomp
Sec-WebSocket-Version: 13
Origin: http://localhost:8080
服务端返回一个如下信息:
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: 1qVdfYHU9hPOl4JYYNXF623Gzn0=
Sec-WebSocket-Protocol: v10.stomp
关于WebSocket的详细信息可以参考RFC 6455。 注意:如果websocket服务器运行在web服务器(例如nginx)之后,需要在web服务器开启websockt以便升级请求能够到到websocket服务器,如果使用云服务,需要确定云服务提供商提供这项功能。
虽然WebSocket的设计是HTTP兼容的并且也是以一个HTTP请求开始,但是它和HTTP有完全不同的架构和编程模型。
在HTTP和REST中,应用有许多URL,客户端通过不同的URL,以请求-响应的模式和服务器交互。服务器通过请求的URL,方法,头将服务路由到合适的处理器。
与之相反,WebSocket通常只有一个URL用来初始化链接。剩下的应用消息都通过同样的TCP连接交流。是一个完全不同的异步,事件驱动,消息架构。
与HTTP协议不同,websocket并不固定内容的任何语义。
WebSocket的客户端和服务端通过Sec-WebSocket-Protocol
头可以协商使用高级消息协议(例如STOMP)。
只需要继承WebSocketHandler
就可以创建一个WebSocket的服务器,或者更具体一点,可以继承TextWebSocketHandler
或者BinaryWebSocketHandler
import org.springframework.web.socket.WebSocketHandler;
import org.springframework.web.socket.WebSocketSession;
import org.springframework.web.socket.TextMessage;
public class MyHandler extends TextWebSocketHandler {
@Override
public void handleTextMessage(WebSocketSession session, TextMessage message) {
// ...
}
}
配置WebSocket的映射URL: Java配置:
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 registry) {
registry.addHandler(myHandler(), "/myHandler");
}
@Bean
public WebSocketHandler myHandler() {
return new MyHandler();
}
}
XML 配置:
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:websocket="http://www.springframework.org/schema/websocket"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/websocket
http://www.springframework.org/schema/websocket/spring-websocket.xsd">
<websocket:handlers>
<websocket:mapping path="/myHandler" handler="myHandler"/>
</websocket:handlers>
<bean id="myHandler" class="org.springframework.samples.MyHandler"/>
</beans>
初始化WebSocket握手最简单的方式是通过HandshakeInterceptor
。它暴露了握手开始前后的两个方法。这样的拦截器可以用来阻止握手或者将有用的信息添加到WebSocketSession
中。例如,内置的HttpSessionHandshakeInterceptor
就可以将HTTP Session的属性添加到WebSocket session中。
Java 配置
@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {
@Override
public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
registry.addHandler(new MyHandler(), "/myHandler")
.addInterceptors(new HttpSessionHandshakeInterceptor());
}
}
XML 配置:
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:websocket="http://www.springframework.org/schema/websocket"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/websocket
http://www.springframework.org/schema/websocket/spring-websocket.xsd">
<websocket:handlers>
<websocket:mapping path="/myHandler" handler="myHandler"/>
<websocket:handshake-interceptors>
<bean class="org.springframework.web.socket.server.support.HttpSessionHandshakeInterceptor"/>
</websocket:handshake-interceptors>
</websocket:handlers>
<bean id="myHandler" class="org.springframework.samples.MyHandler"/>
</beans>
可以通过继承DefaultHandshakeHandler
实现定制握手实现,包括客户端域检查,协商子协议等。
Java WebSocket API(JSR-356)提供了两种部署方式
以上这两种方式都不适合只有一个前端控制器的设计模式。
由于JSR-356的限制,Spring使用RequestUpgradeStrategy
策略部署,Tomcat,Jetty,GlassFish,WebLogic,WebSphere和Undertow都支持这个策略。
JSR-356的另一个缺点是需要在启动的时候进行classpath扫描,这会明显拖慢容器启动速度。
对于Tomcat,WildFly和GlassFish可以配置ServletServerContainerFactoryBean
Java 配置:
@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {
@Bean
public ServletServerContainerFactoryBean createWebSocketContainer() {
ServletServerContainerFactoryBean container = new ServletServerContainerFactoryBean();
container.setMaxTextMessageBufferSize(8192);
container.setMaxBinaryMessageBufferSize(8192);
return container;
}
}
XML 配置:
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:websocket="http://www.springframework.org/schema/websocket"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/websocket
http://www.springframework.org/schema/websocket/spring-websocket.xsd">
<bean class="org.springframework...ServletServerContainerFactoryBean">
<property name="maxTextMessageBufferSize" value="8192"/>
<property name="maxBinaryMessageBufferSize" value="8192"/>
</bean>
</beans>
对于Jetty:
@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {
@Override
public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
registry.addHandler(echoWebSocketHandler(),
"/echo").setHandshakeHandler(handshakeHandler());
}
@Bean
public DefaultHandshakeHandler handshakeHandler() {
WebSocketPolicy policy = new WebSocketPolicy(WebSocketBehavior.SERVER);
policy.setInputBufferSize(8192);
policy.setIdleTimeout(600000);
return new DefaultHandshakeHandler(
new JettyRequestUpgradeStrategy(new WebSocketServerFactory(policy)));
}
}
Jetty 的xml 配置
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:websocket="http://www.springframework.org/schema/websocket"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/websocket
http://www.springframework.org/schema/websocket/spring-websocket.xsd">
<websocket:handlers>
<websocket:mapping path="/echo" handler="echoHandler"/>
<websocket:handshake-handler ref="handshakeHandler"/>
</websocket:handlers>
<bean id="handshakeHandler" class="org.springframework...DefaultHandshakeHandler">
<constructor-arg ref="upgradeStrategy"/>
</bean>
<bean id="upgradeStrategy" class="org.springframework...JettyRequestUpgradeStrategy">
<constructor-arg ref="serverFactory"/>
</bean>
<bean id="serverFactory" class="org.eclipse.jetty...WebSocketServerFactory">
<constructor-arg>
<bean class="org.eclipse.jetty...WebSocketPolicy">
<constructor-arg value="SERVER"/>
<property name="inputBufferSize" value="8092"/>
<property name="idleTimeout" value="600000"/>
</bean>
</constructor-arg>
</bean>
</beans>
Spring实现的WebSocket和SockJs默认不支持跨域请求。如需跨域请求需要进行设置。 对于跨域处理的三种方式:
X-Frame-Options=SAMEREGION
,JSONP被禁止。origin
必须以’http://'或者'https://'开头。在这种模式下,SockJS启用,IFrame和JSONP被禁用origin
设置为*
,SockJS,JSONP,Iframe都支持。Java配置:
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 registry) {
registry.addHandler(myHandler(), "/myHandler").setAllowedOrigins("http://mydomain.com");
}
@Bean
public WebSocketHandler myHandler() {
return new MyHandler();
}
}
XML 配置:
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:websocket="http://www.springframework.org/schema/websocket"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/websocket
http://www.springframework.org/schema/websocket/spring-websocket.xsd">
<websocket:handlers allowed-origins="http://mydomain.com">
<websocket:mapping path="/myHandler" handler="myHandler" />
</websocket:handlers>
<bean id="myHandler" class="org.springframework.samples.MyHandler"/>
</beans>