初识 Netflix Zuul

private void initGroovyFilterManager() {
    //设置GroovyCompiler
    //GroovyCompiler是DynamicCompiler的实现类
    FilterLoader.getInstance().setCompiler(new GroovyCompiler());

    //从配置中是获取过滤器源文件的根目录
    String scriptRoot = System.getProperty("zuul.filter.root", "");
    if (scriptRoot.length() > 0) scriptRoot = scriptRoot + File.separator;
    try {
        //设置文件名过滤器, 这里只过滤`.groovy`类型文件.
        FilterFileManager.setFilenameFilter(new GroovyFileFilter());
        //初始化过滤器文件管理器
        //第一个参数是扫描目录的间隔时间, 单位为秒
        //后面跟要扫描的子目录
        //1. 初始化的时候会扫描各个子目录, 使用文件名过滤器获取到所有的过滤器源文件. 
        //2. 遍历这些文件, 使用`FilterLoader.getInstance().putFilter(file)`, compiler编译之后使用FilterFactory进行实例化, 并添加到过滤器注册表中. 是否实例化的逻辑判断是否在上次修改且文件最后修改时间是否相同. 如果是上次修改之后又有改动, 要重建改类型过滤器的列表. 如果没有修改, 对改文件不做任何处理.
        //3. 启动线程, 每个5秒执行一个1和2的操作.
        FilterFileManager.init(5, scriptRoot + "pre", scriptRoot + "route", scriptRoot + "post");
    } catch (Exception e) {
        throw new RuntimeException(e);
    }
}

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();
    }
}

/**
 * runFilter checks !isFilterDisabled() and shouldFilter(). The run() method is invoked if both are true.
 *
 * @return the return from ZuulFilterResult
 */
public ZuulFilterResult runFilter() {
    ZuulFilterResult zr = new ZuulFilterResult();
    //动态获取`zuul.filerClassName.filterType.disable`的值
    //动态获取使用Archaius的DynamicPropertyFactory获取*, 通过这个可实现动态配置
    if (!isFilterDisabled()) {
        //调用filter类的校验逻辑
        if (shouldFilter()) {
            Tracer t = TracerFactory.instance().startMicroTracer("ZUUL::" + this.getClass().getSimpleName());
            try {
                //执行filter的逻辑处理
                Object res = run();
                //执行成功
                zr = new ZuulFilterResult(res, ExecutionStatus.SUCCESS);
            } catch (Throwable e) {
                t.setName("ZUUL::" + this.getClass().getSimpleName() + " failed");
                //执行失败
                zr = new ZuulFilterResult(ExecutionStatus.FAILED);
                zr.setException(e);
            } finally {
                t.stopAndLog();
            }
        } else {
            //filter不适用, 直接跳过
            zr = new ZuulFilterResult(ExecutionStatus.SKIPPED);
        }
    }
    return zr;
}

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
    throws IOException, ServletException {
    try {
        chain.doFilter(req, res);
    } finally {
        RequestContext.getCurrentContext().unset();
    }
}

public ZuulFilter newInstance(Class clazz) throws InstantiationException, IllegalAccessException {
    return (ZuulFilter) clazz.newInstance();
}