Zuul- 啟動

@EnableZuulProxy

我們使用zuul的時候，就會用這個註解，這個主鍵的功能和Eureka Server一樣。import了ZuulProxyMarkerConfiguration類。

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

}

ZuulProxyMarkerConfiguration類的主要作用是載入了ZuulProxyMarkerConfiguration#Marker類。

@Configuration(proxyBeanMethods = false)
public class ZuulProxyMarkerConfiguration {

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

    class Marker {

    }

}

ZuulServerAutoConfiguration

我們從spring.factories看，可以看到他包括了ZuulServerAutoConfiguration和ZuulProxyAutoConfiguration，這兩個類能不能被載入，他的條件就是有沒有ZuulProxyMarkerConfiguration#Marker類。

zuulRefreshRoutesListener

這個類是ApplicationListener<ApplicationEvent>，當有ContextRefreshedEvent、RefreshScopeRefreshedEvent、RoutesRefreshedEvent、InstanceRegisteredEvent的時候，就會觸發重置，動態路由就是透過這個來實現的。

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

zuulServlet

建立ZuulServlet，這個是HttpServlet，初始化會呼叫init方法，在ZuulServlet#init方法中，會建立一個ZuulRunner物件。

@Bean
@ConditionalOnMissingBean(name = "zuulServlet")
@ConditionalOnProperty(name = "zuul.use-filter", havingValue = "false",
        matchIfMissing = true)
public ServletRegistrationBean zuulServlet() {
    ServletRegistrationBean<ZuulServlet> 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;
}

與zuulServlet類似的是ZuulServletFilter，預設沒有載入。

ZuulRouteApplicationContextInitializer

我們看過Ribbon - 懶載入就知道了，懶載入轉直接載入。

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

ZuulFilterInitializer

先獲取ZuulFilter，然後例項化ZuulFilterInitializer，他有個@PostConstruct註解，所以會呼叫ZuulFilterInitializer#contextInitialized方法。

@Configuration(proxyBeanMethods = false)
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);
    }

}

ZuulFilterInitializer#contextInitialized

在這個方法中，比較重要的就是把ZuulFilter集合存入FilterRegistry的filters中。

@PostConstruct
public void contextInitialized() {
    log.info("Starting filter initializer");

    TracerFactory.initialize(tracerFactory);
    CounterFactory.initialize(counterFactory);

    for (Map.Entry<String, ZuulFilter> entry : this.filters.entrySet()) {
        filterRegistry.put(entry.getKey(), entry.getValue());
    }
}

總結

所以zuul啟動的時候，就會把ZuulFilter集合存入FilterRegistry的filters中。