Zuul- 启动

@EnableZuulProxy

我们使用zuul的时候，就会用这个注解，这个主键的功能和Eureka Server一样。import了ZuulProxyMarkerConfiguration类。

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

}

ZuulProxyMarkerConfiguration类的主要作用是加载了ZuulProxyMarkerConfiguration#Marker类。

@Configuration(proxyBeanMethods = false)
public class ZuulProxyMarkerConfiguration {

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

    class Marker {

    }

}

ZuulServerAutoConfiguration

我们从spring.factories看，可以看到他包括了ZuulServerAutoConfiguration和ZuulProxyAutoConfiguration，这两个类能不能被加载，他的条件就是有没有ZuulProxyMarkerConfiguration#Marker类。

zuulRefreshRoutesListener

这个类是ApplicationListener<ApplicationEvent>，当有ContextRefreshedEvent、RefreshScopeRefreshedEvent、RoutesRefreshedEvent、InstanceRegisteredEvent的时候，就会触发重置，动态路由就是通过这个来实现的。

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

zuulServlet

创建ZuulServlet，这个是HttpServlet，初始化会调用init方法，在ZuulServlet#init方法中，会创建一个ZuulRunner对象。

@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;
}

与zuulServlet类似的是ZuulServletFilter，默认没有加载。

ZuulRouteApplicationContextInitializer

我们看过Ribbon - 懒加载就知道了，懒加载转直接加载。

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

ZuulFilterInitializer

先获取ZuulFilter，然后实例化ZuulFilterInitializer，他有个@PostConstruct注解，所以会调用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

在这个方法中，比较重要的就是把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());
    }
}

总结

所以zuul启动的时候，就会把ZuulFilter集合存入FilterRegistry的filters中。