网关Zuul——url请求流转路径

在springcloud的网关组件zuul中，网关本身能够接收url请求,那么请求在网关zuul组件中是怎么流转的呢？

从前面的文章可以看出，当外部请求传递到网关（Zuul）时，请求会传递到ZuulController类中

public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
        ModelAndView var3;
        try {
            var3 = super.handleRequestInternal(request, response);
        } finally {
            RequestContext.getCurrentContext().unset();
        }

        return var3;
    }

这里可以看出，外部请求会进入ZuulController类中，交由handleRequest方法处理，而该方法实际调用其父类的handleRequestInternal方法

查看ZuulController的父类ServletWrappingController

protected ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response) throws Exception {
        Assert.state(this.servletInstance != null, "No Servlet instance");
        this.servletInstance.service(request, response);
        return null;
    }

在ServletWrappingController类的handleRequestInternal方法中，请求是由ZuulServlet的service方法处理

public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        try {
            this.init((HttpServletRequest)servletRequest, (HttpServletResponse)servletResponse);
            RequestContext context = RequestContext.getCurrentContext();
            context.setZuulEngineRan();

            try {
                this.preRoute();
            } catch (ZuulException var12) {
                this.error(var12);
                this.postRoute();
                return;
            }

            try {
                this.route();
            } catch (ZuulException var13) {
                this.error(var13);
                this.postRoute();
                return;
            }

            try {
                this.postRoute();
            } catch (ZuulException var11) {
                this.error(var11);
            }
        } catch (Throwable var14) {
            this.error(new ZuulException(var14, 500, "UNHANDLED_EXCEPTION_" + var14.getClass().getName()));
        } finally {
            RequestContext.getCurrentContext().unset();
        }
    }

//处理http请求
 void init(HttpServletRequest servletRequest, HttpServletResponse servletResponse) {
        this.zuulRunner.init(servletRequest, servletResponse);
    }

从上述代码可以看出，http请求会传递到ZuulRunner类中进行处理

查看ZuulRunner中的处理方式

   public void init(HttpServletRequest servletRequest, HttpServletResponse servletResponse) {
        RequestContext ctx = RequestContext.getCurrentContext();
        if (this.bufferRequests) {
            ctx.setRequest(new HttpServletRequestWrapper(servletRequest));
        } else {
            ctx.setRequest(servletRequest);
        }

        ctx.setResponse(new HttpServletResponseWrapper(servletResponse));
    }

查看上述代码，可以看出请求最后被存放在RequestContext类中，而RequestContext是一个静态单例的，所以在程序的任何位置都可以通过获取RequestContext的实例来获取到http请求信息。而这也就是过滤器用以进行请求过滤的基础。

总结:

http请求的流转路径：

ZuulController的handleRequest方法——>ServletWrappingController的handleRequestInternal方法——>ZuulServlet的service方法——>ZuulServlet的init方法——>

ZuulRunner的init方法——>RequestContext的实例中

原文地址：https://www.cnblogs.com/AWSL/p/10624204.html