浅谈SpringCloud之zuul源码解析

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<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

@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<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

/**
 * @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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