1. ZuulController，ZuulHanlderMapping內建
1.1 ZuulHanlderMapping
ZuulHanlderMapping的初始化情況如下，在spring mvc的DispatcherServelet的initHandlerMapping方法會初始化ZuulHanlderMapping，BeanFactoryUtils.beansOfTypeIncludingAncestors會找type類型為HandlerMapping.class的所有類注入到handlerMappings.而前面的章節分析過ZuulHanlderMapping在ZuulServer中被注入。
/** List of HandlerMappings used by this servlet */
private List<HandlerMapping> handlerMappings;
private void initHandlerMappings(ApplicationContext context) {
this.handlerMappings = null;
if (this.detectAllHandlerMappings) {
// Find all HandlerMappings in the ApplicationContext, including ancestor contexts.
Map<String, HandlerMapping> matchingBeans =
BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerMappings = new ArrayList<HandlerMapping>(matchingBeans.values());
// We keep HandlerMappings in sorted order.
AnnotationAwareOrderComparator.sort(this.handlerMappings);
}
}
else {
try {
HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class);
this.handlerMappings = Collections.singletonList(hm);
}
catch (NoSuchBeanDefinitionException ex) {
// Ignore, we'll add a default HandlerMapping later.
}
}
// Ensure we have at least one HandlerMapping, by registering
// a default HandlerMapping if no other mappings are found.
if (this.handlerMappings == null) {
this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class);
if (logger.isDebugEnabled()) {
logger.debug("No HandlerMappings found in servlet '" + getServletName() + "': using default");
}
}
}
ZuulHanlderMapping的源碼如下圖：可以看到ZuulHanlderMapping在registerHandlers中擷取了所有路由關系，然後把path跟ZuulController作為key，value寫入到handlerMap，this.handlerMap.put(urlPath,ResolvedHandler).這樣會根據相關的path，找到相對應的controller處理請求。
public class ZuulHandlerMapping extends AbstractUrlHandlerMapping {
private final RouteLocator routeLocator;
private final ZuulController zuul;
private ErrorController errorController;
private PathMatcher pathMatcher = new AntPathMatcher();
private volatile boolean dirty = true;
public ZuulHandlerMapping(RouteLocator routeLocator, ZuulController zuul) {
this.routeLocator = routeLocator;
this.zuul = zuul;
setOrder(-200);
}
@Override
protected HandlerExecutionChain getCorsHandlerExecutionChain(HttpServletRequest request,
HandlerExecutionChain chain, CorsConfiguration config) {
if (config == null) {
// Allow CORS requests to go to the backend
return chain;
}
return super.getCorsHandlerExecutionChain(request, chain, config);
}
public void setErrorController(ErrorController errorController) {
this.errorController = errorController;
}
public void setDirty(boolean dirty) {
this.dirty = dirty;
if (this.routeLocator instanceof RefreshableRouteLocator) {
((RefreshableRouteLocator) this.routeLocator).refresh();
}
}
@Override
protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {
if (this.errorController != null && urlPath.equals(this.errorController.getErrorPath())) {
return null;
}
if (isIgnoredPath(urlPath, this.routeLocator.getIgnoredPaths())) 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);
}
private boolean isIgnoredPath(String urlPath, Collection<String> ignored) {
if (ignored != null) {
for (String ignoredPath : ignored) {
if (this.pathMatcher.match(ignoredPath, urlPath)) {
return true;
}
}
}
return false;
}
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);
}
}
}
}
1.2 ZuulController
zuulController繼承ServletWrappingController，并設定ServletClass為zuul的核心類zuulServlet，在實際調用中，相關邏輯委托給了zuulServlet處理。
import org.springframework.web.servlet.mvc.ServletWrappingController;
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();
}
}
}
1.3 調用鍊路
網關啟動後，請求的鍊路怎麼到達zuul的filter處理，這裡主要是容器跟spring mvc web相關的内容，隻做簡單分析。
zuul過濾器的入口處理類是ZuulServlet.service方法。下圖是其調用方法棧。
DiapatchServlet.doDispatch的主要邏輯如下
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
HttpServletRequest processedRequest = request;
HandlerExecutionChain mappedHandler = null;
boolean multipartRequestParsed = false;
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
try {
ModelAndView mv = null;
Exception dispatchException = null;
try {
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request);
// Determine handler for the current request.
mappedHandler = getHandler(processedRequest);
if (mappedHandler == null || mappedHandler.getHandler() == null) {
noHandlerFound(processedRequest, response);
return;
}
// Determine handler adapter for the current request.
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
// Process last-modified header, if supported by the handler.
String method = request.getMethod();
boolean isGet = "GET".equals(method);
if (isGet || "HEAD".equals(method)) {
long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
if (logger.isDebugEnabled()) {
logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);
}
if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
return;
}
}
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
// Actually invoke the handler.
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
if (asyncManager.isConcurrentHandlingStarted()) {
return;
}
applyDefaultViewName(processedRequest, mv);
mappedHandler.applyPostHandle(processedRequest, response, mv);
}
catch (Exception ex) {
dispatchException = ex;
}
catch (Throwable err) {
// As of 4.3, we're processing Errors thrown from handler methods as well,
// making them available for @ExceptionHandler methods and other scenarios.
dispatchException = new NestedServletException("Handler dispatch failed", err);
}
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}
catch (Exception ex) {
triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
}
catch (Throwable err) {
triggerAfterCompletion(processedRequest, response, mappedHandler,
new NestedServletException("Handler processing failed", err));
}
finally {
if (asyncManager.isConcurrentHandlingStarted()) {
// Instead of postHandle and afterCompletion
if (mappedHandler != null) {
mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
}
}
else {
// Clean up any resources used by a multipart request.
if (multipartRequestParsed) {
cleanupMultipart(processedRequest);
}
}
}
}
主要過一下ZuulHandlerMapping跟zuulController在其中的邏輯，ZuulHandlerMapping在mappedHandler = getHandler(processedRequest);這段代碼的邏輯中，周遊handlerMappings（前面提了ZuulHandlerMapping會被初始化到該集合中）
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
for (HandlerMapping hm : this.handlerMappings) {
if (logger.isTraceEnabled()) {
logger.trace(
"Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'");
}
HandlerExecutionChain handler = hm.getHandler(request);
if (handler != null) {
return handler;
}
}
return null;
}
hm.getHandler(request)代碼如下：
@Override
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
Object handler = getHandlerInternal(request);
if (handler == null) {
handler = getDefaultHandler();
}
if (handler == null) {
return null;
}
// Bean name or resolved handler?
if (handler instanceof String) {
String handlerName = (String) handler;
handler = getApplicationContext().getBean(handlerName);
}
HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
if (CorsUtils.isCorsRequest(request)) {
CorsConfiguration globalConfig = this.globalCorsConfigSource.getCorsConfiguration(request);
CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
}
return executionChain;
}
Object handler = getHandlerInternal(request);代碼調用如下：
@Override
protected Object getHandlerInternal(HttpServletRequest request) throws Exception {
String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
Object handler = lookupHandler(lookupPath, request);
if (handler == null) {
// We need to care for the default handler directly, since we need to
// expose the PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE for it as well.
Object rawHandler = null;
if ("/".equals(lookupPath)) {
rawHandler = getRootHandler();
}
if (rawHandler == null) {
rawHandler = getDefaultHandler();
}
if (rawHandler != null) {
// Bean name or resolved handler?
if (rawHandler instanceof String) {
String handlerName = (String) rawHandler;
rawHandler = getApplicationContext().getBean(handlerName);
}
validateHandler(rawHandler, request);
handler = buildPathExposingHandler(rawHandler, lookupPath, lookupPath, null);
}
}
if (handler != null && logger.isDebugEnabled()) {
logger.debug("Mapping [" + lookupPath + "] to " + handler);
}
else if (handler == null && logger.isTraceEnabled()) {
logger.trace("No handler mapping found for [" + lookupPath + "]");
}
return handler;
}
走到Object handler = lookupHandler(lookupPath, request)；調用ZuulHandlerMapping.lookupHandler方法。該方法會根據前一章節分析的路由規則，把urlPath跟zuulController對應關聯起來。
@Override
protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {
if (this.errorController != null && urlPath.equals(this.errorController.getErrorPath())) {
return null;
}
if (isIgnoredPath(urlPath, this.routeLocator.getIgnoredPaths())) 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);
}
private boolean isIgnoredPath(String urlPath, Collection<String> ignored) {
if (ignored != null) {
for (String ignoredPath : ignored) {
if (this.pathMatcher.match(ignoredPath, urlPath)) {
return true;
}
}
}
return false;
}
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);
}
}
}
整個鍊路調用如下：
回到DispatcherServlet中，真正處理handle時會傳入mappedHandler.getHandler()，即該path對應的controller：ZuulController，前面說了ZuulController的真正處理類是ZuulServlet。這裡需要注意的是，如果該path在路由關系中不存在，則handler為null，通過/error調用相關的錯誤處理controller（BasicErrorController）傳回404錯誤頁面。
1.4 zuul-core ZuulServlet調用邏輯
ZuulServlet.service方法，代碼邏輯比較清晰，執行preRoute->route->postRoute，在執行preRoute跟route出現zuulException是執行error，postRoute。postRoute異常則執行error。無法捕獲的異常，則轉換成error(new ZuulException(e, 500, “UNHANDLED_EXCEPTION_” + e.getClass().getName()));
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();
}
}
preRoute,route,postRoute,error調用相關的filter邏輯一樣，責任鍊模式，執行類找到相關類型（filterType）的過濾器按順序（filterOrder）執行。核心邏輯如下：至于怎麼找到相關的filter，在前面篇章@EnableZuulServer初始化已經說明。
public Object runFilters(String sType) throws Throwable {
if (RequestContext.getCurrentContext().debugRouting()) {
Debug.addRoutingDebug("Invoking {" + sType + "} type filters");
}
boolean bResult = false;
List<ZuulFilter> list = FilterLoader.getInstance().getFiltersByType(sType);
if (list != null) {
for (int i = 0; i < list.size(); i++) {
ZuulFilter zuulFilter = list.get(i);
Object result = processZuulFilter(zuulFilter);
if (result != null && result instanceof Boolean) {
bResult |= ((Boolean) result);
}
}
}
return bResult;
}