spring cloud 網關，依賴于netflix 下的zuul 組件
zuul 的流程是，自定義 了zuulservletfilter和zuulservlet兩種方式，讓開發者可以去實現，并調用
先來看下zuulservletfilter的實現片段
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@override public void dofilter(servletrequest servletrequest, servletresponse servletresponse, filterchain filterchain) throws ioexception, servletexception { try { init((httpservletrequest) servletrequest, (httpservletresponse) servletresponse); try { prerouting(); } catch (zuulexception e) { error(e); postrouting(); return; } // only forward onto to the chain if a zuul response is not being sent if (!requestcontext.getcurrentcontext().sendzuulresponse()) { filterchain.dofilter(servletrequest, servletresponse); return; } try { routing(); } catch (zuulexception e) { error(e); postrouting(); return; } try { postrouting(); } catch (zuulexception e) { error(e); return; } } catch (throwable e) { error(new zuulexception(e, 500, "uncaught_exception_from_filter_" + e.getclass().getname())); } finally { requestcontext.getcurrentcontext().unset(); } } |
從上面的代碼可以看到，比較關心的是prerouting、routing,postrouting三個方法 ，這三個方法會調用 注冊為zuulfilter的子類，首先來看下這三個方法
prerouting: 是路由前會做一些內容
routing():開始路由事項
postrouting：路由結束，不管是否有錯誤都會經過該方法
那這三個方法是怎么和zuulfilter聯系在一起的呢？
先來分析下 prerouting:
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void postrouting() throws zuulexception { zuulrunner.postroute(); } |
同時 zuulrunner再來調用
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public void postroute() throws zuulexception { filterprocessor.getinstance().postroute();} |
最終調用 filterprocessor 的 runfilters
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public void preroute() throws zuulexception { try { runfilters("pre"); } catch (zuulexception e) { throw e; } catch (throwable e) { throw new zuulexception(e, 500, "uncaught_exception_in_pre_filter_" + e.getclass().getname()); }} |
看到了runfilters 是通過 filtertype(pre ,route ,post )來過濾出已經注冊的 zuulfilter:
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public object runfilters(string stype) throws throwable { if (requestcontext.getcurrentcontext().debugrouting()) { debug.addroutingdebug("invoking {" + stype + "} type filters"); } boolean bresult = false; //通過stype獲取 zuulfilter的列表 list<zuulfilter> list = filterloader.getinstance().getfiltersbytype(stype); if (list != null) { for (int i = 0; i < list.size(); i++) { zuulfilter zuulfilter = list.get(i); object result = processzuulfilter(zuulfilter); if (result != null && result instanceof boolean) { bresult |= ((boolean) result); } } } return bresult; } |
再來看下 zuulfilter的定義
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public abstract class zuulfilter implements izuulfilter, comparable<zuulfilter> { private final dynamicbooleanproperty filterdisabled = dynamicpropertyfactory.getinstance().getbooleanproperty(disablepropertyname(), false); /** * to classify a filter by type. standard types in zuul are "pre" for pre-routing filtering, * "route" for routing to an origin, "post" for post-routing filters, "error" for error handling. * we also support a "static" type for static responses see staticresponsefilter. * any filtertype made be created or added and run by calling filterprocessor.runfilters(type) * * @return a string representing that type */ abstract public string filtertype(); /** * filterorder() must also be defined for a filter. filters may have the same filterorder if precedence is not * important for a filter. filterorders do not need to be sequential. * * @return the int order of a filter */ abstract public int filterorder(); /** * by default zuulfilters are static; they don't carry state. this may be overridden by overriding the isstaticfilter() property to false * * @return true by default */ public boolean isstaticfilter() { return true; } |
只列出了一部分字段，但可以看到filtertype和filterorder兩個字段，這兩個分別是指定filter是什么類型，排序
這兩個決定了實現的zuulfilter會在什么階段被執行，按什么順序執行
當選擇好已經注冊的zuulfilter后，會調用zuulfilter的runfilter
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public zuulfilterresult runfilter() { zuulfilterresult zr = new zuulfilterresult(); if (!isfilterdisabled()) { if (shouldfilter()) { tracer t = tracerfactory.instance().startmicrotracer("zuul::" + this.getclass().getsimplename()); try { object res = run(); zr = new zuulfilterresult(res, executionstatus.success); } catch (throwable e) { t.setname("zuul::" + this.getclass().getsimplename() + " failed"); zr = new zuulfilterresult(executionstatus.failed); zr.setexception(e); } finally { t.stopandlog(); } } else { zr = new zuulfilterresult(executionstatus.skipped); } } return zr; } |
其中run 是一個zuulfilter的一個抽象方法
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public interface izuulfilter { /** * a "true" return from this method means that the run() method should be invoked * * @return true if the run() method should be invoked. false will not invoke the run() method */ boolean shouldfilter(); /** * if shouldfilter() is true, this method will be invoked. this method is the core method of a zuulfilter * * @return some arbitrary artifact may be returned. current implementation ignores it. */ object run();} |
所以，實現zuulfilter的子類要重寫 run方法，我們來看下 其中一個階段的實現 predecorationfilter 這個類是spring cloud封裝的在使用zuul 作為轉發的代碼服務器時進行封裝的對象，目的是為了決定當前的要轉發的請求是按serviceid，http請求，還是forward來作轉發
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@override public object run() { requestcontext ctx = requestcontext.getcurrentcontext(); final string requesturi = this.urlpathhelper.getpathwithinapplication(ctx.getrequest()); route route = this.routelocator.getmatchingroute(requesturi); if (route != null) { string location = route.getlocation(); if (location != null) { ctx.put("requesturi", route.getpath()); ctx.put("proxy", route.getid()); if (!route.iscustomsensitiveheaders()) { this.proxyrequesthelper .addignoredheaders(this.properties.getsensitiveheaders().toarray(new string[0])); } else { this.proxyrequesthelper.addignoredheaders(route.getsensitiveheaders().toarray(new string[0])); } if (route.getretryable() != null) { ctx.put("retryable", route.getretryable()); } // 如果配置的轉發地址是http開頭，會設置 routehost if (location.startswith("http:") || location.startswith("https:")) { ctx.setroutehost(geturl(location)); ctx.addoriginresponseheader("x-zuul-service", location); } // 如果配置的轉發地址forward，則會設置forward.to else if (location.startswith("forward:")) { ctx.set("forward.to", stringutils.cleanpath(location.substring("forward:".length()) + route.getpath())); ctx.setroutehost(null); return null; } else { // 否則以serviceid進行轉發 // set serviceid for use in filters.route.ribbonrequest ctx.set("serviceid", location); ctx.setroutehost(null); ctx.addoriginresponseheader("x-zuul-serviceid", location); } if (this.properties.isaddproxyheaders()) { addproxyheaders(ctx, route); string xforwardedfor = ctx.getrequest().getheader("x-forwarded-for"); string remoteaddr = ctx.getrequest().getremoteaddr(); if (xforwardedfor == null) { xforwardedfor = remoteaddr; } else if (!xforwardedfor.contains(remoteaddr)) { // prevent duplicates xforwardedfor += ", " + remoteaddr; } ctx.addzuulrequestheader("x-forwarded-for", xforwardedfor); } if (this.properties.isaddhostheader()) { ctx.addzuulrequestheader("host", tohostheader(ctx.getrequest())); } } } else { log.warn("no route found for uri: " + requesturi); string fallbackuri = requesturi; string fallbackprefix = this.dispatcherservletpath; // default fallback // servlet is // dispatcherservlet if (requestutils.iszuulservletrequest()) { // remove the zuul servletpath from the requesturi log.debug("zuulservletpath=" + this.properties.getservletpath()); fallbackuri = fallbackuri.replacefirst(this.properties.getservletpath(), ""); log.debug("replaced zuul servlet path:" + fallbackuri); } else { // remove the dispatcherservlet servletpath from the requesturi log.debug("dispatcherservletpath=" + this.dispatcherservletpath); fallbackuri = fallbackuri.replacefirst(this.dispatcherservletpath, ""); log.debug("replaced dispatcherservlet servlet path:" + fallbackuri); } if (!fallbackuri.startswith("/")) { fallbackuri = "/" + fallbackuri; } string forwarduri = fallbackprefix + fallbackuri; forwarduri = forwarduri.replaceall("//", "/"); ctx.set("forward.to", forwarduri); } return null; } |
這個前置處理，是為了后面決定以哪種zuulfilter來處理當前的請求 ，如 simplehostroutingfilter，這個的filtertype是post ,當 ``predecorationfilter設置了requestcontext中的 routehost，如 simplehostroutingfilter中的判斷
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@overridepublic boolean shouldfilter() { return requestcontext.getcurrentcontext().getroutehost() != null && requestcontext.getcurrentcontext().sendzuulresponse();} |
在 simplehostroutingfilter中的run中，真正實現地址轉發的內容，其實質是調用 httpclient進行請求
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@override public object run() { requestcontext context = requestcontext.getcurrentcontext(); httpservletrequest request = context.getrequest(); multivaluemap<string, string> headers = this.helper .buildzuulrequestheaders(request); multivaluemap<string, string> params = this.helper .buildzuulrequestqueryparams(request); string verb = getverb(request); inputstream requestentity = getrequestbody(request); if (request.getcontentlength() < 0) { context.setchunkedrequestbody(); } string uri = this.helper.buildzuulrequesturi(request); this.helper.addignoredheaders(); try { httpresponse response = forward(this.httpclient, verb, uri, request, headers, params, requestentity); setresponse(response); } catch (exception ex) { context.set(error_status_code, httpservletresponse.sc_internal_server_error); context.set("error.exception", ex); } return null; } |
最后如果是成功能，會調用 注冊 為post的zuulfilter ,目前有兩個 senderrorfilter 和 sendresponsefilter 這兩個了，一個是處理錯誤，一個是處理成功的結果
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持服務器之家。
原文鏈接：https://www.jianshu.com/p/295e51bc1518
