[TOC]

ZUUL 流程分析

开始

注解@EnableZuulProxy 上有一个 @Import(ZuulProxyMarkerConfiguration.class)-> 把 Maker初始化为Spring的Bean.

这时可以通过源码的注释,或者MATA-INF/spring.factories

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.cloud.netflix.zuul.ZuulServerAutoConfiguration,\
org.springframework.cloud.netflix.zuul.ZuulProxyAutoConfiguration

源码如下:

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/**
 * Responsible for adding in a marker bean to trigger activation of
 * {@link ZuulProxyAutoConfiguration}.  // 源码注释里有写
 *
 * @author Biju Kunjummen
 */

@Configuration(proxyBeanMethods = false)
public class ZuulProxyMarkerConfiguration {
	@Bean
	public Marker zuulProxyMarkerBean() {
		return new Marker();
	}
	class Marker {
	}
}

上面的两个类都是通过 @EnableAutoConfiguration加载, 这两个类上都有

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@ConditionalOnBean(ZuulServerMarkerConfiguration.Marker.class)

表示,要有这个Maker这个Bean才会加载,这就是开始的 EnableZuulProxy 开始的标志.

ZuulServerAutoConfiguration

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@Bean
@ConditionalOnMissingBean(name = "zuulServlet")
@ConditionalOnProperty(name = "zuul.use-filter", havingValue = "false",
                       matchIfMissing = true)
public ServletRegistrationBean zuulServlet() {
    ServletRegistrationBean<ZuulServlet> servlet = new ServletRegistrationBean<>(
        new ZuulServlet(), this.zuulProperties.getServletPattern());
    // The whole point of exposing this servlet is to provide a route that doesn't
    // buffer requests.
    servlet.addInitParameter("buffer-requests", "false");
    return servlet;
}

@Bean
@ConditionalOnMissingBean(name = "zuulServletFilter")
@ConditionalOnProperty(name = "zuul.use-filter", havingValue = "true",
                       matchIfMissing = false)
public FilterRegistrationBean zuulServletFilter() {
    final FilterRegistrationBean<ZuulServletFilter> filterRegistration = new FilterRegistrationBean<>();
    filterRegistration.setUrlPatterns(
        Collections.singleton(this.zuulProperties.getServletPattern()));
    filterRegistration.setFilter(new ZuulServletFilter());
    // 顺序为 Integer.MAX_VALUE
    filterRegistration.setOrder(Ordered.LOWEST_PRECEDENCE);
    // The whole point of exposing this servlet is to provide a route that doesn't
    // buffer requests.
    filterRegistration.addInitParameter("buffer-requests", "false");
    return filterRegistration;
}

ZuulServlet和ZuulServletFilter 是zuul提供的两种启动方式, 对应了servlet和servlet Filter. 通过配置文件切换,默认为ZuulServlet

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zuul:
  use-filter: true # ZuulServletFilter

这两种方式,处理逻辑基本是差不多的.关键是ZuulRunner,FilterProcessor核心处理类.

4种类型对应的ZuulFilter列表

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# com.netflix.zuul.FilterLoader
private final ConcurrentHashMap<String, List<ZuulFilter>> hashFiltersByType = new ConcurrentHashMap<String, List<ZuulFilter>>();

ZuulServlet

com.netflix.zuul.http.ZuulServlet#service

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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 {
             // 按顺序执行 pre ZuulFilter
            preRoute();
        } catch (ZuulException e) {
            // 按顺序执行 error ZuulFilter
            error(e);
            // 按顺序执行 post ZuulFilter
            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();
    }
}

ZuulServletFilter

还有一个是. ZuulServletFilter 中 init 方法 生成了 ZuulRunner zuulRunner;

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zuul:
  use-filter: true
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@Override
   public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
       try {
           init((HttpServletRequest) servletRequest, (HttpServletResponse) servletResponse);
           try {
               // 按顺序执行 pre ZuulFilter
               preRouting();
           } catch (ZuulException e) {
                // 按顺序执行 error ZuulFilter
               error(e);
               // 按顺序执行 post ZuulFilter
               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 {
                // 按顺序执行 route ZuulFilter
               routing();
           } catch (ZuulException e) {
                // 按顺序执行 error ZuulFilter
               error(e);
                 // 按顺序执行 post ZuulFilter
               postRouting();
               return;
           }
           try {
               // 按顺序执行 post ZuulFilter
               postRouting();
           } catch (ZuulException e) {
                // 按顺序执行 error ZuulFilter
               error(e);
               return;
           }
       } catch (Throwable e) {
           error(new ZuulException(e, 500, "UNCAUGHT_EXCEPTION_FROM_FILTER_" + e.getClass().getName()));
       } finally {
           RequestContext.getCurrentContext().unset();
       }
   }