一，开启ZUUL支持标识

加入zuul一般如下

@EnableZuulProxy @SpringCloudApplication public class Application {      public static void main(String[] args) {     new SpringApplicationBuilder(Application.class).web(true).run(args);   }    }

其中@EnableZuulProxy是开启zuul的功能支持。

跟踪进EnableZuulProxy，源码如下

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

除了引入discoveryClient注册eureka外，主要就做了一件事，引入了ZuulProxyMarkerConfiguration，@Import(ZuulProxyMarkerConfiguration.class), ZuulProxyMarkerConfiguration新建了个Marker的bean返回。

如下：

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

后面的zuul配置会根据是否有这个maker对象而使配置生效

@ConditionalOnBean(ZuulServerMarkerConfiguration.Marker.class)

二，zuul初始化配置

更多初始化具体的配置，zuul是用的SPI方式进行

SPI入口

用SPI管理所有注册，spring.factories如下：

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\ org.springframework.cloud.netflix.archaius.ArchaiusAutoConfiguration,\ org.springframework.cloud.netflix.feign.ribbon.FeignRibbonClientAutoConfiguration,\ org.springframework.cloud.netflix.feign.FeignAutoConfiguration,\ org.springframework.cloud.netflix.feign.encoding.FeignAcceptGzipEncodingAutoConfiguration,\ org.springframework.cloud.netflix.feign.encoding.FeignContentGzipEncodingAutoConfiguration,\ org.springframework.cloud.netflix.hystrix.HystrixAutoConfiguration,\ org.springframework.cloud.netflix.hystrix.security.HystrixSecurityAutoConfiguration,\ org.springframework.cloud.netflix.ribbon.RibbonAutoConfiguration,\ org.springframework.cloud.netflix.rx.RxJavaAutoConfiguration,\ org.springframework.cloud.netflix.metrics.servo.ServoMetricsAutoConfiguration,\ org.springframework.cloud.netflix.zuul.ZuulServerAutoConfiguration,\ org.springframework.cloud.netflix.zuul.ZuulProxyAutoConfiguration org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker=\ org.springframework.cloud.netflix.hystrix.HystrixCircuitBreakerConfiguration org.springframework.boot.env.EnvironmentPostProcessor=\ org.springframework.cloud.netflix.metrics.ServoEnvironmentPostProcessor

其中和zuul相关初始化的主要是

org.springframework.cloud.netflix.zuul.ZuulServerAutoConfiguration

和

org.springframework.cloud.netflix.zuul.ZuulProxyAutoConfiguration

1. ZuulServerAutoConfiguration

@Configuration @EnableConfigurationProperties({ ZuulProperties.class }) @ConditionalOnClass(ZuulServlet.class) @ConditionalOnBean(ZuulServerMarkerConfiguration.Marker.class)   //这里用到上面的@EnableZuulProxy的引入做判断  // 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;  ... ...

属性相关

ZuulProperties zuulProperties;   // yml里的配置，zuul开头相关配置在这注入

ServerProperties server;    // yml里的配置，zuul开头相关配置在这注入

ErrorController errorController; //处理错误的controller,自定义实现

几个重要bean：

ZuulController   接管所有的请求，把所有请求交给zuulServlet去处理,所有请求会先到zuulcontroler再转到zuulServlet

ZuulRefreshListener   通过监听spring Context发布机制事件，监听心跳消息

几个重要Filter：

按ORDER的从小到大排列

ServletDetectionFilter  -- PRE -3.  判断是否是走spring MVC还是直接走zuulservlet的， 并赋值 IS_DISPATCHER_SERVLET_REQUEST_KEY

Servlet30RequestWrapper -PRE -2. 把RequestServlet转换Servlet30RequestWrapper

FormBodyWrapperFilter -PRE -1. 封装成FormBodyRequestWrapper

DebugFilter   -PRE  1.  用于动态开启debug日志，zuul.debug.request=true 开启debug模式

还几个核心flter注册在 org.springframework.cloud.netflix.zuul.ZuulProxyAutoConfiguration

PreDecorationFilter PRE 5,  PreDecorationFilter  添加头，serviceId信息处理等

2, ZuulProxyAutoConfiguration

@Configuration @Import({ RibbonCommandFactoryConfiguration.RestClientRibbonConfiguration.class, 		RibbonCommandFactoryConfiguration.OkHttpRibbonConfiguration.class, 		RibbonCommandFactoryConfiguration.HttpClientRibbonConfiguration.class }) @ConditionalOnBean(ZuulProxyMarkerConfiguration.Marker.class) public class ZuulProxyAutoConfiguration extends ZuulServerAutoConfiguration {  	@SuppressWarnings("rawtypes") 	@Autowired(required = false) 	private List<RibbonRequestCustomizer> requestCustomizers = Collections.emptyList();  	@Autowired 	private DiscoveryClient discovery;  	@Autowired 	private ServiceRouteMapper serviceRouteMapper;

导入Ribbon相关的类

属性相关

DiscoveryClient discovery; // eureka客户端, eureka相关操作，如：根据serviceId获取实例所有机器列表

重要的Filter

PreDecorationFilter   // 处理请求头，serviceId等信息的地方

RibbonRoutingFilter.  //真正做转发的Filter，封装了nitfilx 全家桶的地方

SimpleHostRoutingFilter // 转发不走eureka的请求