SpringCloud之zuul源碼解析

                                             Zuul源碼解析    

    zuul各版本實現存在一些微小的變化，總的實現思想未改變，以spring-cloud-netflix-core-1.3.6.RELEASE爲例

  一、zuul的重要的初始化類

    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

初始化路由規則

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

      初始化ZuulFilterInitializer

      初始化ZuulHandlerMapping

      代碼如下

    //路由規則
    @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繼承ZuulServerAutoConfiguration功能上和zuulServerAutoConfiguration

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

 ZuulFilterInitializer

該類的作用主要是把初始化的過濾器註冊到zuul的FilterRegistry，FilterRegistry是一個單例用於初始化路由信息，在ZuulRunner中使用

RibbonCommandFactoryConfiguration

  主要作用是配置轉發的實現，實現主要有apache，okhttp

二、zuul的轉發實現

首先第一步轉到ZuulHandlerMapping中的lookupHandler方法，把轉發轉到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);
    }

  第一次訪問時dirty爲true會初始化一次請求規則如下

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繼承ServletWrappingController的會把請求轉到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方法如下主要執行pre,route,postRoute三種路由器

 @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、最後由SendResponseFilter執行返回結果,filterOrder爲1000所以最好post的filter不要超過1000否則影響返回結果