SpringCloud之zuul源码的示例分析

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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

 //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 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

@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

private void registerHandlers() { Collection 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

/** * @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

 @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

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