SpringCloud源码| zuul源码

zuul主要使用责任链设计模式

其中有如下过滤器

pre过滤器

-3：ServletDetectionFilter
-2：Servlet30WrapperFilter
-1：FromBodyWrapperFilter
1：DebugFilter
5：PreDecorationFilter

routing过滤器

10：RibbonRoutingFilter
100：SimpleHostRoutingFilter
500：SendForwardFilter

post过滤器

0：SendErrorFilter
900：LocationRewriteFilter
1000：SendResponseFilter

@EnableZuulProxy为spring cloud中zuul的入口

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@EnableCircuitBreaker
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Import(ZuulProxyMarkerConfiguration.class)
public @interface EnableZuulProxy {

}

然后在ZuulProxyAutoConfiguration进行相关类的注册

经过断点调试，核心逻辑为此方法ZuulServlet#service

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@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
        //从threadlocal中获取线程独有的RequestContext
        RequestContext context = RequestContext.getCurrentContext();
        context.setZuulEngineRan();
		
        //先执行pre过滤器
        try {
            preRoute();
        } catch (ZuulException e) {
            //若执行失败，则执行post过滤器 并返回
            error(e);
            postRoute();
            return;
        }
        //执行route过滤器
        try {
            route();
        } catch (ZuulException e) {
            //报错则执行post过滤器 并返回
            error(e);
            postRoute();
            return;
        }
        //若报错则再重试一遍
        try {
            postRoute();
        } catch (ZuulException e) {
            error(e);
            return;
        }

    } catch (Throwable e) {
        error(new ZuulException(e, 500, "UNHANDLED_EXCEPTION_" + e.getClass().getName()));
    } finally {
        //执行完毕之后，回收threadlocal中的context
        RequestContext.getCurrentContext().unset();
    }
}