zuul1.3源码扒一扒（1）

先开个头吧

作为偶尔点进源码的时候看到东西，或是学到，或是不解，或是惊讶，之后的一些记录。从springcloud各个组件开始吧，计划文段保持间断，只道出核心点，不过各个文段保持连续。

zuul作为spring cloud 推荐网关，搭建起来很方便。

Spring Cloud 1.4.4 core jar包里面的package基本描述了整个微服务架构的核心部分，其中zuul也囊括其中。

在使用zuul时我们会使用EnableZuulProxy注解，配合使用spring cloud。

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

@EnableCircuitBreaker 默认使用断路器 参考文档：https://martinfowler.com/bliki/CircuitBreaker.html

@Import(ZuulProxyMarkerConfiguration.class)就技巧了。

@Configuration
public class ZuulProxyMarkerConfiguration {
   @Bean
   public Marker zuulProxyMarkerBean() {
      return new Marker();
   }

   class Marker {
   }
}

啥都没干，就是配置了个zuulProxyMarkerBean。看字面意思就猜差不多了，这个东西可以用于标记，标记都是用来判断什么用的。
用于ZuulProxyAutoConfiguration的ConditionalOnBean，也就是使用EnableZuulProxy注解连带的开启了ZuulProxyAutoConfiguration的配置。

还有个注解 EnableZuulServer 一样有个ZuulServerMarkerConfiguration 一样的道理。
事实上EnableZuulProxy是EnableZuulServer的增强版，为什么，因为ZuulProxyAutoConfiguration继承ZuulServerAutoConfiguration。

那么zuul的配置文件里有什么呢？我觉得最重要的一个spring cloud网关要组合两个组件：一个是Ribbon，一个是hystrix，后者签名通过EnableCircuitBreaker搞进来了，后续在写。
核心关注两个类：ZuulProxyAutoConfiguration 和 ZuulServerAutoConfiguration

@Configuration
@Import({ RibbonCommandFactoryConfiguration.RestClientRibbonConfiguration.class,
		RibbonCommandFactoryConfiguration.OkHttpRibbonConfiguration.class,
		RibbonCommandFactoryConfiguration.HttpClientRibbonConfiguration.class,
		HttpClientConfiguration.class })
@ConditionalOnBean(ZuulProxyMarkerConfiguration.Marker.class)
public class ZuulProxyAutoConfiguration extends ZuulServerAutoConfiguration {

	@SuppressWarnings("rawtypes")
	@Autowired(required = false)
	private List<RibbonRequestCustomizer> requestCustomizers = Collections.emptyList();

	@Autowired(required = false)
	private Registration registration;

	@Autowired
	private DiscoveryClient discovery;

	@Autowired
	private ServiceRouteMapper serviceRouteMapper;

	@Override
	public HasFeatures zuulFeature() {
		return HasFeatures.namedFeature("Zuul (Discovery)",
				ZuulProxyAutoConfiguration.class);
	}

	@Bean
	@ConditionalOnMissingBean(DiscoveryClientRouteLocator.class)
	public DiscoveryClientRouteLocator discoveryRouteLocator() {
		return new DiscoveryClientRouteLocator(this.server.getServletPrefix(),
				this.discovery, this.zuulProperties, this.serviceRouteMapper, this.registration);
	}

	// pre filters
	@Bean
	public PreDecorationFilter preDecorationFilter(RouteLocator routeLocator,
			ProxyRequestHelper proxyRequestHelper) {
		return new PreDecorationFilter(routeLocator, this.server.getServletPrefix(),
				this.zuulProperties, proxyRequestHelper);
	}

	// route filters
	@Bean
	public RibbonRoutingFilter ribbonRoutingFilter(ProxyRequestHelper helper,
			RibbonCommandFactory<?> ribbonCommandFactory) {
		RibbonRoutingFilter filter = new RibbonRoutingFilter(helper, ribbonCommandFactory,
				this.requestCustomizers);
		return filter;
	}

	@Bean
	@ConditionalOnMissingBean({SimpleHostRoutingFilter.class, CloseableHttpClient.class})
	public SimpleHostRoutingFilter simpleHostRoutingFilter(ProxyRequestHelper helper,
			ZuulProperties zuulProperties,
			ApacheHttpClientConnectionManagerFactory connectionManagerFactory,
			ApacheHttpClientFactory httpClientFactory) {
		return new SimpleHostRoutingFilter(helper, zuulProperties,
				connectionManagerFactory, httpClientFactory);
	}

	@Bean
	@ConditionalOnMissingBean({SimpleHostRoutingFilter.class})
	public SimpleHostRoutingFilter simpleHostRoutingFilter2(ProxyRequestHelper helper,
														   ZuulProperties zuulProperties,
														   CloseableHttpClient httpClient) {
		return new SimpleHostRoutingFilter(helper, zuulProperties,
				httpClient);
	}

	@Bean
	public ApplicationListener<ApplicationEvent> zuulDiscoveryRefreshRoutesListener() {
		return new ZuulDiscoveryRefreshListener();
	}

	@Bean
	@ConditionalOnMissingBean(ServiceRouteMapper.class)
	public ServiceRouteMapper serviceRouteMapper() {
		return new SimpleServiceRouteMapper();
	}

	@Configuration
	@ConditionalOnMissingClass("org.springframework.boot.actuate.endpoint.Endpoint")
	protected static class NoActuatorConfiguration {

		@Bean
		public ProxyRequestHelper proxyRequestHelper(ZuulProperties zuulProperties) {
			ProxyRequestHelper helper = new ProxyRequestHelper();
			helper.setIgnoredHeaders(zuulProperties.getIgnoredHeaders());
			helper.setTraceRequestBody(zuulProperties.isTraceRequestBody());
			return helper;
		}

	}

	@Configuration
	@ConditionalOnClass(Endpoint.class)
	protected static class EndpointConfiguration {

		@Autowired(required = false)
		private TraceRepository traces;

		@ConditionalOnEnabledEndpoint("routes")
		@Bean
		public RoutesEndpoint routesEndpoint(RouteLocator routeLocator) {
			return new RoutesEndpoint(routeLocator);
		}

		@ConditionalOnEnabledEndpoint("routes")
		@Bean
		public RoutesMvcEndpoint routesMvcEndpoint(RouteLocator routeLocator,
				RoutesEndpoint endpoint) {
			return new RoutesMvcEndpoint(endpoint, routeLocator);
		}

		@ConditionalOnEnabledEndpoint("filters")
		@Bean
		public FiltersEndpoint filtersEndpoint() {
			FilterRegistry filterRegistry = FilterRegistry.instance();
			return new FiltersEndpoint(filterRegistry);
		}

		@Bean
		public ProxyRequestHelper proxyRequestHelper(ZuulProperties zuulProperties) {
			TraceProxyRequestHelper helper = new TraceProxyRequestHelper();
			if (this.traces != null) {
				helper.setTraces(this.traces);
			}
			helper.setIgnoredHeaders(zuulProperties.getIgnoredHeaders());
			helper.setTraceRequestBody(zuulProperties.isTraceRequestBody());
			return helper;
		}
	}

	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);
		}

	}

}

@Configuration
@EnableConfigurationProperties({ ZuulProperties.class })
@ConditionalOnClass(ZuulServlet.class)
@ConditionalOnBean(ZuulServerMarkerConfiguration.Marker.class)
// Make sure to get the ServerProperties from the same place as a normal web app would
@Import(ServerPropertiesAutoConfiguration.class)
public class ZuulServerAutoConfiguration {

	@Autowired
	protected ZuulProperties zuulProperties;

	@Autowired
	protected ServerProperties server;

	@Autowired(required = false)
	private ErrorController errorController;

	@Bean
	public HasFeatures zuulFeature() {
		return HasFeatures.namedFeature("Zuul (Simple)", ZuulServerAutoConfiguration.class);
	}

	@Bean
	@Primary
	public CompositeRouteLocator primaryRouteLocator(
			Collection<RouteLocator> routeLocators) {
		return new CompositeRouteLocator(routeLocators);
	}

	@Bean
	@ConditionalOnMissingBean(SimpleRouteLocator.class)
	public SimpleRouteLocator simpleRouteLocator() {
		return new SimpleRouteLocator(this.server.getServletPrefix(),
				this.zuulProperties);
	}

	@Bean
	public ZuulController zuulController() {
		return new ZuulController();
	}

	@Bean
	public ZuulHandlerMapping zuulHandlerMapping(RouteLocator routes) {
		ZuulHandlerMapping mapping = new ZuulHandlerMapping(routes, zuulController());
		mapping.setErrorController(this.errorController);
		return mapping;
	}

	@Bean
	public ApplicationListener<ApplicationEvent> zuulRefreshRoutesListener() {
		return new ZuulRefreshListener();
	}

	@Bean
	@ConditionalOnMissingBean(name = "zuulServlet")
	public ServletRegistrationBean zuulServlet() {
		ServletRegistrationBean servlet = new ServletRegistrationBean(new ZuulServlet(),
				this.zuulProperties.getServletPattern());
		// The whole point of exposing this servlet is to provide a route that doesn't
		// buffer requests.
		servlet.addInitParameter("buffer-requests", "false");
		return servlet;
	}

	// pre filters

	@Bean
	public ServletDetectionFilter servletDetectionFilter() {
		return new ServletDetectionFilter();
	}

	@Bean
	public FormBodyWrapperFilter formBodyWrapperFilter() {
		return new FormBodyWrapperFilter();
	}

	@Bean
	public DebugFilter debugFilter() {
		return new DebugFilter();
	}

	@Bean
	public Servlet30WrapperFilter servlet30WrapperFilter() {
		return new Servlet30WrapperFilter();
	}

	// post filters

	@Bean
	public SendResponseFilter sendResponseFilter() {
		return new SendResponseFilter();
	}

	@Bean
	public SendErrorFilter sendErrorFilter() {
		return new SendErrorFilter();
	}

	@Bean
	public SendForwardFilter sendForwardFilter() {
		return new SendForwardFilter();
	}

	@Bean
	@ConditionalOnProperty(value = "zuul.ribbon.eager-load.enabled", matchIfMissing = false)
	public ZuulRouteApplicationContextInitializer zuulRoutesApplicationContextInitiazer(
			SpringClientFactory springClientFactory) {
		return new ZuulRouteApplicationContextInitializer(springClientFactory,
				zuulProperties);
	}

	@Configuration
	protected static class ZuulFilterConfiguration {

		@Autowired
		private Map<String, ZuulFilter> filters;

		@Bean
		public ZuulFilterInitializer zuulFilterInitializer(
				CounterFactory counterFactory, TracerFactory tracerFactory) {
			FilterLoader filterLoader = FilterLoader.getInstance();
			FilterRegistry filterRegistry = FilterRegistry.instance();
			return new ZuulFilterInitializer(this.filters, counterFactory, tracerFactory, filterLoader, filterRegistry);
		}

	}

	@Configuration
	@ConditionalOnClass(CounterService.class)
	protected static class ZuulCounterFactoryConfiguration {

		@Bean
		@ConditionalOnBean(CounterService.class)
		public CounterFactory counterFactory(CounterService counterService) {
			return new DefaultCounterFactory(counterService);
		}
	}

	@Configuration
	protected static class ZuulMetricsConfiguration {

		@Bean
		@ConditionalOnMissingBean(CounterFactory.class)
		public CounterFactory counterFactory() {
			return new EmptyCounterFactory();
		}

		@ConditionalOnMissingBean(TracerFactory.class)
		@Bean
		public TracerFactory tracerFactory() {
			return new EmptyTracerFactory();
		}

	}

	private static class ZuulRefreshListener
			implements ApplicationListener<ApplicationEvent> {

		@Autowired
		private ZuulHandlerMapping zuulHandlerMapping;

		private HeartbeatMonitor heartbeatMonitor = new HeartbeatMonitor();

		@Override
		public void onApplicationEvent(ApplicationEvent event) {
			if (event instanceof ContextRefreshedEvent
					|| event instanceof RefreshScopeRefreshedEvent
					|| event instanceof RoutesRefreshedEvent) {
				this.zuulHandlerMapping.setDirty(true);
			}
			else if (event instanceof HeartbeatEvent) {
				if (this.heartbeatMonitor.update(((HeartbeatEvent) event).getValue())) {
					this.zuulHandlerMapping.setDirty(true);
				}
			}
		}

	}

}