Spring Cloud Zuul遗失的世界(一)

@SpringBootApplication
@EnableZuulProxy
public class SpringCloudZuulApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringCloudZuulApplication.class, args);
    }
}

@EnableCircuitBreaker
@EnableDiscoveryClient
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Import(ZuulProxyConfiguration.class)
public @interface EnableZuulProxy {
}

@Configuration
@Import({ RibbonCommandFactoryConfiguration.RestClientRibbonConfiguration.class,
		RibbonCommandFactoryConfiguration.OkHttpRibbonConfiguration.class,
		RibbonCommandFactoryConfiguration.HttpClientRibbonConfiguration.class })
public class ZuulProxyConfiguration extends ZuulConfiguration {
	@SuppressWarnings("rawtypes")
	@Autowired(required = false)
	private List<RibbonRequestCustomizer> requestCustomizers = Collections.emptyList();
    // DiscoveryClient肩负着从Eureka中获取服务列表,获取对应实例的功能
	@Autowired
	private DiscoveryClient discovery;
	@Autowired
	private ServiceRouteMapper serviceRouteMapper;
   
    // zuulFeature 依然是将Zuul标识为Discovery模式.
    @Override
	public HasFeatures zuulFeature() {
		return HasFeatures.namedFeature("Zuul (Discovery)", ZuulProxyConfiguration.class);
	}
    @Bean
	@ConditionalOnMissingBean(DiscoveryClientRouteLocator.class)
	public DiscoveryClientRouteLocator discoveryRouteLocator() {
		return new DiscoveryClientRouteLocator(this.server.getServletPrefix(), this.discovery, this.zuulProperties,
				this.serviceRouteMapper);
	}
  
    // 依然是注册了这么个ApplicationEvent来触发上文中的dirty状态.
    @Bean
	public ApplicationListener<ApplicationEvent> zuulDiscoveryRefreshRoutesListener() {
		return new ZuulDiscoveryRefreshListener();
	}
    
    private static class ZuulDiscoveryRefreshListener implements ApplicationListener<ApplicationEvent> {
		private HeartbeatMonitor monitor = new HeartbeatMonitor();
		@Autowired
		private ZuulHandlerMapping zuulHandlerMapping;
		@Override
		public void onApplicationEvent(ApplicationEvent event) {
			if (event instanceof InstanceRegisteredEvent) {
				reset();
			}
			else if (event instanceof ParentHeartbeatEvent) {
				ParentHeartbeatEvent e = (ParentHeartbeatEvent) event;
				resetIfNeeded(e.getValue());
			}
			else if (event instanceof HeartbeatEvent) {
				HeartbeatEvent e = (HeartbeatEvent) event;
				resetIfNeeded(e.getValue());
			}
		}
		private void resetIfNeeded(Object value) {
			if (this.monitor.update(value)) {
				reset();
			}
		}
		private void reset() {
			this.zuulHandlerMapping.setDirty(true);
		}
	}
    //其余省略
}

@Configuration
@EnableConfigurationProperties({ ZuulProperties.class })
@ConditionalOnClass(ZuulServlet.class)
// Make sure to get the ServerProperties from the same place as a normal web app would
@Import(ServerPropertiesAutoConfiguration.class)
public class ZuulConfiguration {
    //zuulProperties 对应配置文件的内容
	@Autowired
	protected ZuulProperties zuulProperties;
	@Autowired
	protected ServerProperties server;
	@Autowired(required = false)
	private ErrorController errorController;
    //告知actuator监控当前模式:Simple/Discovery
    @Override
	public HasFeatures zuulFeature() {
		return HasFeatures.namedFeature("Zuul (Discovery)", ZuulProxyConfiguration.class);
	}
    
   //通过继承ServletWrappingController接管了上文定义的ZuulServlet,因此ZuulController就是Zuul的入口
   @Bean
	public ZuulController zuulController() {
		return new ZuulController();
	}
   /**
    *ZuulHandlerMapping,响应器模式,其实目前就是把所有路径的请求导入到ZuulController上.</br>
    *另外的功效是当觉察RouteLocator路由表变更,则更新自己dirty状态,重新注册所有Route到ZuulController.
    */
   @Bean
	public ZuulHandlerMapping zuulHandlerMapping(RouteLocator routes) {
		ZuulHandlerMapping mapping = new ZuulHandlerMapping(routes, zuulController());
		mapping.setErrorController(this.errorController);
		return mapping;
	}
   /**
   * ZuulRefreshListener,
   */
   private static class ZuulRefreshListener
			implements ApplicationListener<ApplicationEvent> {
		@Autowired
		private ZuulHandlerMapping zuulHandlerMapping;
		private HeartbeatMonitor heartbeatMonitor = new HeartbeatMonitor();
		@Override
		public void onApplicationEvent(ApplicationEvent event) {
            // Simple模式下注册RoutesRefreshedEvent,解析配置文件,
            // 维护路由表并监听变化,将请求都导向ZuulController去历经filters
			if (event instanceof ContextRefreshedEvent
					|| event instanceof RefreshScopeRefreshedEvent
					|| event instanceof RoutesRefreshedEvent) {
				this.zuulHandlerMapping.setDirty(true);
			} 
            // Endpoint模式下又添加了HeartbeatEvent
			else if (event instanceof HeartbeatEvent) {
				if (this.heartbeatMonitor.update(((HeartbeatEvent) event).getValue())) {
					this.zuulHandlerMapping.setDirty(true);
				}
			}
		}
	}
   //其余省略
}

public class ZuulController extends ServletWrappingController {
	public ZuulController() {
		setServletClass(ZuulServlet.class);
		setServletName("zuul");
		setSupportedMethods((String[]) null); // Allow all
	}
	@Override
	public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
		try {
			// We don't care about the other features of the base class, just want to
			// handle the request
			return super.handleRequestInternal(request, response);
		}
		finally {
			// @see com.netflix.zuul.context.ContextLifecycleFilter.doFilter
			RequestContext.getCurrentContext().unset();
		}
	}
}