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浅谈SpringCloud之zuul源码解析

时间:2021-04-06 11:48     来源/作者:小兵成长记

zuul各版本实现存在一些微小的变化,总的实现思想未改变,以spring-cloud-netflix-core-1.3.6.RELEASE为例

一、zuul的重要的初始化类

org.springframework.cloud.netflix.zuul.ZuulServerAutoConfiguration

org.springframework.cloud.netflix.zuul.ZuulProxyAutoConfiguration

org.springframework.cloud.netflix.zuul.ZuulFilterInitializer

org.springframework.cloud.netflix.zuul.RibbonCommandFactoryConfiguration

ZuulServerAutoConfiguration

初始化路由规则

初始化一些重要的filter如 PreDecorationFilter,RibbonRoutingFilter

初始化ZuulFilterInitializer

初始化ZuulHandlerMapping

代码如下

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

ZuulProxyAutoConfiguration

zuulProxAutoConfiguration继承ZuulServerAutoConfiguration功能上和zuulServerAutoConfiguration

主要功能是增加了RibbonCommandFactoryConfiguration的配置,初始化所有的实现ribbon的方式如apache,okhttp。

ZuulFilterInitializer

该类的作用主要是把初始化的过滤器注册到zuul的FilterRegistry,FilterRegistry是一个单例用于初始化路由信息,在ZuulRunner中使用

RibbonCommandFactoryConfiguration

  主要作用是配置转发的实现,实现主要有apache,okhttp

二、zuul的转发实现

首先第一步转到ZuulHandlerMapping中的lookupHandler方法,把转发转到zuulController中

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@Override
 protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {
 if (this.errorController != null && urlPath.equals(this.errorController.getErrorPath())) {
  return null;
 }
 String[] ignored = this.routeLocator.getIgnoredPaths().toArray(new String[0]);
 if (PatternMatchUtils.simpleMatch(ignored, urlPath)) {
  return null;
 }
 RequestContext ctx = RequestContext.getCurrentContext();
 if (ctx.containsKey("forward.to")) {
  return null;
 }
 if (this.dirty) {
  synchronized (this) {
  if (this.dirty) {
   registerHandlers();
   this.dirty = false;
  }
  }
 }
 return super.lookupHandler(urlPath, request);
 }

第一次访问时dirty为true会初始化一次请求规则如下

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private void registerHandlers() {
 Collection<Route> routes = this.routeLocator.getRoutes();
 if (routes.isEmpty()) {
  this.logger.warn("No routes found from RouteLocator");
 }
 else {
  for (Route route : routes) {
  registerHandler(route.getFullPath(), this.zuul);
  }
 }
 }

第二步ZuulController继承ServletWrappingController的会把请求转到ZuulServlet中如下

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/**
 * @author Spencer Gibb
 */
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();
 }
 }
}

第三步ZuulServlet的service方法如下主要执行pre,route,postRoute三种路由器

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@Override
 public void service(javax.servlet.ServletRequest servletRequest, javax.servlet.ServletResponse servletResponse) throws ServletException, IOException {
   try {
     init((HttpServletRequest) servletRequest, (HttpServletResponse) servletResponse);
     // Marks this request as having passed through the "Zuul engine", as opposed to servlets
     // explicitly bound in web.xml, for which requests will not have the same data attached
     RequestContext context = RequestContext.getCurrentContext();
     context.setZuulEngineRan();
     try {
       preRoute();
     } catch (ZuulException e) {
       error(e);
       postRoute();
       return;
     }
     try {
       route();
     } catch (ZuulException e) {
       error(e);
       postRoute();
       return;
     }
     try {
       postRoute();
     } catch (ZuulException e) {
       error(e);
       return;
     }
   } catch (Throwable e) {
     error(new ZuulException(e, 500, "UNHANDLED_EXCEPTION_" + e.getClass().getName()));
   } finally {
     RequestContext.getCurrentContext().unset();
   }
 }

四、最后由SendResponseFilter执行返回结果,filterOrder为1000所以最好post的filter不要超过1000否则影响返回结果

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持服务器之家。

原文链接:https://my.oschina.net/u/136848/blog/1621259

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