zuul各版本实现存在一些微小的变化，总的实现思想未改变，以spring-cloud-netflix-core-1.3.6.RELEASE为例
一、zuul的重要的初始化类
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
初始化路由规则
初始化一些重要的filter如 PreDecorationFilter，RibbonRoutingFilter
初始化ZuulFilterInitializer
初始化ZuulHandlerMapping
代码如下
//路由规则
@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继承ZuulServerAutoConfiguration功能上和zuulServerAutoConfiguration
主要功能是增加了RibbonCommandFactoryConfiguration的配置，初始化所有的实现ribbon的方式如apache,okhttp。
ZuulFilterInitializer
该类的作用主要是把初始化的过滤器注册到zuul的FilterRegistry，FilterRegistry是一个单例用于初始化路由信息，在ZuulRunner中使用
RibbonCommandFactoryConfiguration
主要作用是配置转发的实现，实现主要有apache，okhttp
二、zuul的转发实现
首先第一步转到ZuulHandlerMapping中的lookupHandler方法，把转发转到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);
}
第一次访问时dirty为true会初始化一次请求规则如下
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继承ServletWrappingController的会把请求转到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方法如下主要执行pre,route,postRoute三种路由器
@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、最后由SendResponseFilter执行返回结果,filterOrder为1000所以最好post的filter不要超过1000否则影响返回结果
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