spring cloud 入门实践系列 - zuul源码理解

从两条线分析zuul的源代码

1 启动加载配置

ZuulProxyConfiguration

2 请求访问zuul服务

http://172.16.153.1:8963/firstapi/firstapi/speak?words=zxlhgggggggg

列表内容

StandardHostValve invoke方法 （tomcat） 入口

DispatcherServlet 类的doDispatch方法 拦截

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
...
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;
}
...
}

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;
}

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[/code]

AbstractHandlerMapping 类的getHandler方法

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.corsConfigSource.getCorsConfiguration(request);
CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
}
return executionChain;
}

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[/code]

AbstractUrlHandlerMapping 类的getHandlerInternal方法

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;
}

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[/code]

ZuulHandlerMapping 类的lookupHandler方法

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);
}

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[/code]

最终是在super的lookupHandler方法中找到handler了，也就是在AbstractUrlHandlerMapping类的lookupHandler方法中获取到。



可见path最终都是映射到同一个handler即ZuulController。

ZuulController handler

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();
}
}

}

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[/code]

ServletWrappingController handleRequestInternal

protected ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response)
throws Exception {

this.servletInstance.service(request, response);
return null;
}

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[/code]

ZuulServlet handler

@Override
public void service(javax.servlet.ServletRequest servletRequest, javax.servlet.ServletResponse servletResponse) throws ServletException, IOException {
try {
init((HttpServletRequest) servletRequest, (HttpServletResponse) servletResponse);
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();
}
}

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[/code]

ZuulRunner

public void preRoute() throws ZuulException {
FilterProcessor.getInstance().preRoute();
}
public void route() throws ZuulException {
FilterProcessor.getInstance().route();
}
public void postRoute() throws ZuulException {
FilterProcessor.getInstance().postRoute();
}

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[/code]

FilterProcessor

public void preRoute() throws ZuulException {
try {
runFilters("pre");
} catch (ZuulException e) {
throw e;
} catch (Throwable e) {
throw new ZuulException(e, 500, "UNCAUGHT_EXCEPTION_IN_PRE_FILTER_" + e.getClass().getName());
}
}
public void route() throws ZuulException {
try {
runFilters("route");
} catch (ZuulException e) {
throw e;
} catch (Throwable e) {
throw new ZuulException(e, 500, "UNCAUGHT_EXCEPTION_IN_ROUTE_FILTER_" + e.getClass().getName());
}
}
public void postRoute() throws ZuulException {
try {
runFilters("post");
} catch (ZuulException e) {
throw e;
} catch (Throwable e) {
throw new ZuulException(e, 500, "UNCAUGHT_EXCEPTION_IN_POST_FILTER_" + e.getClass().getName());
}
}
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;
}

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[/code]

pre包含如下filter



route包含如下filter



post包含如下filter



那么对远程服务调用的封装，也是在Filter里面，我们可以看下

@Override
public Object run() {
RequestContext context = RequestContext.getCurrentContext();
this.helper.addIgnoredHeaders();
try {
RibbonCommandContext commandContext = buildCommandContext(context);
ClientHttpResponse response = forward(commandContext);
setResponse(response);
return response;
}
catch (ZuulException ex) {
throw new ZuulRuntimeException(ex);
}
catch (Exception ex) {
throw new ZuulRuntimeException(ex);
}
}
protected ClientHttpResponse forward(RibbonCommandContext context) throws Exception {
Map<String, Object> info = this.helper.debug(context.getMethod(),
context.getUri(), context.getHeaders(), context.getParams(),
context.getRequestEntity());

RibbonCommand command = this.ribbonCommandFactory.create(context);
try {
ClientHttpResponse response = command.execute();
this.helper.appendDebug(info, response.getStatusCode().value(),
response.getHeaders());
return response;
}
catch (HystrixRuntimeException ex) {
return handleException(info, ex);
}

}

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[/code]

forward方法中的command.execute即是对远程服务的调用。

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