Spring5高级编程------Spring-WebSocket中STOMP配置的加载机制

技术2022-07-12 64

Spring-WebSocket中STOMP配置的加载机制

WebSocketMessageBrokerConfigurer配置类的加载一、注解@EnableWebSocketMessageBroker二、DelegatingWebSocketMessageBrokerConfiguration配置类三、WebSocketMessageBrokerConfigurationSupport抽象类四、AbstractMessageBrokerConfiguration抽象类五、STOMP配置中的三个关键接口1、StompEndpointRegistry2、StompWebSocketEndpointRegistration3、SockJsServiceRegistration

WebSocketMessageBrokerConfigurer配置类的加载

一、注解@EnableWebSocketMessageBroker

将这个注释添加到一个@Configuration类中，这样就可以使用更高级的消息传递子协议在WebSocket上启用代理支持的消息传递。@EnableWebSocketMessageBroker注解的主要作用就是引入一个配置类DelegatingWebSocketMessageBrokerConfiguration

package org.springframework.web.socket.config.annotation; import java.lang.annotation.Documented; import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; import org.springframework.context.annotation.Import; /** * Add this annotation to an {@code @Configuration} class to enable broker-backed * messaging over WebSocket using a higher-level messaging sub-protocol. * */ @Retention(RetentionPolicy.RUNTIME) @Target(ElementType.TYPE) @Documented @Import(DelegatingWebSocketMessageBrokerConfiguration.class) public @interface EnableWebSocketMessageBroker { }

将这个注解放在自定义的WebSocketMessageBrokerConfigurer实现类上即可实现STOMP配置的自动加载，自定义STOMP配置类如下（@Configuration注解不是必须的，也可以使用@Import注解直接在主配置类中引入该配置类）：

import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker; import org.springframework.context.annotation.Configuration; @EnableWebSocketMessageBroker @Configuration public class WebSocketStompConfiguration implements WebSocketMessageBrokerConfigurer { }

注意：WebSocketMessageBrokerConfigurer有一个空实现的抽象类AbstractWebSocketMessageBrokerConfigurer，由于WebSocketMessageBrokerConfigurer接口提供了默认实现，所以AbstractWebSocketMessageBrokerConfigurer已被废弃，这里不建议使用继承AbstractWebSocketMessageBrokerConfigurer的方式配置。

二、DelegatingWebSocketMessageBrokerConfiguration配置类

@EnableWebSocketMessageBroker 注解使用@Import()注解引入了该配置类源码如下：

package org.springframework.web.socket.config.annotation; import java.util.ArrayList; import java.util.List; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.annotation.Configuration; import org.springframework.messaging.converter.MessageConverter; import org.springframework.messaging.handler.invocation.HandlerMethodArgumentResolver; import org.springframework.messaging.handler.invocation.HandlerMethodReturnValueHandler; import org.springframework.messaging.simp.config.ChannelRegistration; import org.springframework.messaging.simp.config.MessageBrokerRegistry; import org.springframework.util.CollectionUtils; /** * A {@link WebSocketMessageBrokerConfigurationSupport} extension that detects * beans of type {@link WebSocketMessageBrokerConfigurer} and delegates to all * of them allowing callback style customization of the configuration provided * in {@link WebSocketMessageBrokerConfigurationSupport}. * * <p>This class is typically imported via {@link EnableWebSocketMessageBroker}. * * @author Rossen Stoyanchev * @since 4.0 */ @Configuration public class DelegatingWebSocketMessageBrokerConfiguration extends WebSocketMessageBrokerConfigurationSupport { private final List<WebSocketMessageBrokerConfigurer> configurers = new ArrayList<>(); @Autowired(required = false) public void setConfigurers(List<WebSocketMessageBrokerConfigurer> configurers) { if (!CollectionUtils.isEmpty(configurers)) { this.configurers.addAll(configurers); } } @Override protected void registerStompEndpoints(StompEndpointRegistry registry) { for (WebSocketMessageBrokerConfigurer configurer : this.configurers) { configurer.registerStompEndpoints(registry); } } @Override protected void configureWebSocketTransport(WebSocketTransportRegistration registration) { for (WebSocketMessageBrokerConfigurer configurer : this.configurers) { configurer.configureWebSocketTransport(registration); } } @Override protected void configureClientInboundChannel(ChannelRegistration registration) { for (WebSocketMessageBrokerConfigurer configurer : this.configurers) { configurer.configureClientInboundChannel(registration); } } @Override protected void configureClientOutboundChannel(ChannelRegistration registration) { for (WebSocketMessageBrokerConfigurer configurer : this.configurers) { configurer.configureClientOutboundChannel(registration); } } @Override protected void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) { for (WebSocketMessageBrokerConfigurer configurer : this.configurers) { configurer.addArgumentResolvers(argumentResolvers); } } @Override protected void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> returnValueHandlers) { for (WebSocketMessageBrokerConfigurer configurer : this.configurers) { configurer.addReturnValueHandlers(returnValueHandlers); } } @Override protected boolean configureMessageConverters(List<MessageConverter> messageConverters) { boolean registerDefaults = true; for (WebSocketMessageBrokerConfigurer configurer : this.configurers) { if (!configurer.configureMessageConverters(messageConverters)) { registerDefaults = false; } } return registerDefaults; } @Override protected void configureMessageBroker(MessageBrokerRegistry registry) { for (WebSocketMessageBrokerConfigurer configurer : this.configurers) { configurer.configureMessageBroker(registry); } } }

这个配置类的第一个作用是发现并收集Spring容器中的所有WebSocketMessageBrokerConfigurer类型的配置类，代码如下：

private final List<WebSocketMessageBrokerConfigurer> configurers = new ArrayList<>(); @Autowired(required = false) public void setConfigurers(List<WebSocketMessageBrokerConfigurer> configurers) { if (!CollectionUtils.isEmpty(configurers)) { this.configurers.addAll(configurers); } }

这个配置类的第二个作用是实现父类的8个方法，在这8个方法中会遍历获取所有WebSocketMessageBrokerConfigurer 类并分别调用对应的配置方法，从而引入用户自定义的配置，代码如下（这里只列举一个，其他7个类似）：

@Override protected void registerStompEndpoints(StompEndpointRegistry registry) { for (WebSocketMessageBrokerConfigurer configurer : this.configurers) { configurer.registerStompEndpoints(registry); } }

三、WebSocketMessageBrokerConfigurationSupport抽象类

WebSocketMessageBrokerConfigurationSupport是DelegatingWebSocketMessageBrokerConfiguration的抽象父类。其中包含2个需要DelegatingWebSocketMessageBrokerConfiguration实现的方法：

public abstract class WebSocketMessageBrokerConfigurationSupport extends AbstractMessageBrokerConfiguration { protected void configureWebSocketTransport(WebSocketTransportRegistration registry) { } protected abstract void registerStompEndpoints(StompEndpointRegistry registry); }

四、AbstractMessageBrokerConfiguration抽象类

AbstractMessageBrokerConfiguration是DelegatingWebSocketMessageBrokerConfiguration的抽象父类。其中包含6个需要DelegatingWebSocketMessageBrokerConfiguration实现的方法：

public abstract class AbstractMessageBrokerConfiguration implements ApplicationContextAware { protected void configureClientInboundChannel(ChannelRegistration registration) { } protected void configureClientOutboundChannel(ChannelRegistration registration) { } protected void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) { } protected void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> returnValueHandlers) { } protected boolean configureMessageConverters(List<MessageConverter> messageConverters) { return true; } protected void configureMessageBroker(MessageBrokerRegistry registry) { } }