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我们的产品主打金融服务领域#xff0c;以B端客户为我们的核心合作伙伴#xff0c;然而#xff0c;我们的服务最终将惠及C端消费者。在技术实现上#xff0c;我们采用了公司自主研发的微服务框架#xff0c;该框架基于SpringBoot#xff0c;旨在提供高效、可靠的服…引言
我们的产品主打金融服务领域以B端客户为我们的核心合作伙伴然而我们的服务最终将惠及C端消费者。在技术实现上我们采用了公司自主研发的微服务框架该框架基于SpringBoot旨在提供高效、可靠的服务支持。
本文继《生产问题排查系列——未知404状态接口请求》之后深入探讨并扩展了对我们公司自主研发框架的理解。在上一篇文章中我们通过应用性能管理工具定位并解决了持续出现的404请求问题。
代码实例
下面给出一个简单的示例方面读者在后续源码阅读中能着我们的排查思路一起来看上述问题。
pom.xml中引入Spring Boot以及Spring MVC
?xml version1.0 encodingUTF-8?
project xmlnshttp://maven.apache.org/POM/4.0.0xmlns:xsihttp://www.w3.org/2001/XMLSchema-instancexsi:schemaLocationhttp://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsdmodelVersion4.0.0/modelVersionparentgroupIdorg.springframework.boot/groupIdartifactIdspring-boot-starter-parent/artifactIdversion2.7.14/versionrelativePath/ !-- lookup parent from repository --/parentgroupIdorg.example/groupIdartifactIdspringmvc/artifactIdversion1.0-SNAPSHOT/versionpropertiesmaven.compiler.source8/maven.compiler.sourcemaven.compiler.target8/maven.compiler.target/propertiesdependenciesdependencygroupIdorg.springframework.boot/groupIdartifactIdspring-boot-starter-web/artifactId/dependencydependencygroupIdorg.springframework.boot/groupIdartifactIdspring-boot-starter-test/artifactIdscopetest/scope/dependencydependencygroupIdorg.springframework.boot/groupIdartifactIdspring-boot-starter-actuator/artifactId/dependency/dependenciesbuildpluginsplugingroupIdorg.springframework.boot/groupIdartifactIdspring-boot-maven-plugin/artifactId/plugin/plugins/build/projectTestController定义一个请求接口
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;Controller
public class TestController {RequestMapping(/test)ResponseBodypublic String test(){return ok;}
}
源码阅读
下面我们将从一个Spring提供的Health监控请求一步一步分析Spring MVC是如何转发请求的。
Spring MVC所有的接口请求都将由doDispatch方法负责转发。源码如下
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);// 确定当前请求处理的实际处理类mappedHandler getHandler(processedRequest);if (mappedHandler null) {noHandlerFound(processedRequest, response);return;}// 确定当前请求的处理程序适配器。HandlerAdapter ha getHandlerAdapter(mappedHandler.getHandler());// 如果处理程序支持则处理上次修改的标头。String method request.getMethod();boolean isGet HttpMethod.GET.matches(method);if (isGet || HttpMethod.HEAD.matches(method)) {long lastModified ha.getLastModified(request, mappedHandler.getHandler());if (new ServletWebRequest(request, response).checkNotModified(lastModified) isGet) {return;}}if (!mappedHandler.applyPreHandle(processedRequest, response)) {return;}// 调用处理程序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) {// 从4.3开始我们也在处理处理程序方法抛出的错误//使它们可用于ExceptionHandler方法和其他场景。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()) {// 而不是postHandle和afterCompletionif (mappedHandler ! null) {mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);}}else {// 清理由多部分请求使用的所有资源。if (multipartRequestParsed) {cleanupMultipart(processedRequest);}}}}监控接口请求会转发给AbstractHandlerMethodAdapter.handle方法处理源码如下
public final ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)throws Exception {return handleInternal(request, response, (HandlerMethod) handler);}
然后请求会转发到AbstractHandlerMethodAdapter.handleInternal方法中源码如下
protected ModelAndView handleInternal(HttpServletRequest request,HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {ModelAndView mav;checkRequest(request);// 如果需要在同步块中执行invokeHandlerMethod。if (this.synchronizeOnSession) {HttpSession session request.getSession(false);if (session ! null) {Object mutex WebUtils.getSessionMutex(session);synchronized (mutex) {mav invokeHandlerMethod(request, response, handlerMethod);}}else {// 没有可用的HttpSession-不需要互斥mav invokeHandlerMethod(request, response, handlerMethod);}}else {// 根本不需要对会话进行同步。。。mav invokeHandlerMethod(request, response, handlerMethod);}if (!response.containsHeader(HEADER_CACHE_CONTROL)) {if (getSessionAttributesHandler(handlerMethod).hasSessionAttributes()) {applyCacheSeconds(response, this.cacheSecondsForSessionAttributeHandlers);}else {prepareResponse(response);}}return mav;}然后接口请求会转发到RequestMappingHandlerAdapter.invokeHandlerMethod进行一系列参数填充后调用invokeAndHandle方法源码如下
protected ModelAndView invokeHandlerMethod(HttpServletRequest request,HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {ServletWebRequest webRequest new ServletWebRequest(request, response);try {WebDataBinderFactory binderFactory getDataBinderFactory(handlerMethod);ModelFactory modelFactory getModelFactory(handlerMethod, binderFactory);ServletInvocableHandlerMethod invocableMethod createInvocableHandlerMethod(handlerMethod);if (this.argumentResolvers ! null) {invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);}if (this.returnValueHandlers ! null) {invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);}invocableMethod.setDataBinderFactory(binderFactory);invocableMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);ModelAndViewContainer mavContainer new ModelAndViewContainer();mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));modelFactory.initModel(webRequest, mavContainer, invocableMethod);mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect);AsyncWebRequest asyncWebRequest WebAsyncUtils.createAsyncWebRequest(request, response);asyncWebRequest.setTimeout(this.asyncRequestTimeout);WebAsyncManager asyncManager WebAsyncUtils.getAsyncManager(request);asyncManager.setTaskExecutor(this.taskExecutor);asyncManager.setAsyncWebRequest(asyncWebRequest);asyncManager.registerCallableInterceptors(this.callableInterceptors);asyncManager.registerDeferredResultInterceptors(this.deferredResultInterceptors);if (asyncManager.hasConcurrentResult()) {Object result asyncManager.getConcurrentResult();mavContainer (ModelAndViewContainer) asyncManager.getConcurrentResultContext()[0];asyncManager.clearConcurrentResult();LogFormatUtils.traceDebug(logger, traceOn - {String formatted LogFormatUtils.formatValue(result, !traceOn);return Resume with async result [ formatted ];});invocableMethod invocableMethod.wrapConcurrentResult(result);}invocableMethod.invokeAndHandle(webRequest, mavContainer);if (asyncManager.isConcurrentHandlingStarted()) {return null;}return getModelAndView(mavContainer, modelFactory, webRequest);}finally {webRequest.requestCompleted();}}此时请求会转发到ServletInvocableHandlerMethod.invokeAndHandle,之后调用InvocableHandlerMethod.invokeForRequest执行方法源码如下
public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,Object... providedArgs) throws Exception {Object returnValue invokeForRequest(webRequest, mavContainer, providedArgs);setResponseStatus(webRequest);if (returnValue null) {if (isRequestNotModified(webRequest) || getResponseStatus() ! null || mavContainer.isRequestHandled()) {disableContentCachingIfNecessary(webRequest);mavContainer.setRequestHandled(true);return;}}else if (StringUtils.hasText(getResponseStatusReason())) {mavContainer.setRequestHandled(true);return;}mavContainer.setRequestHandled(false);Assert.state(this.returnValueHandlers ! null, No return value handlers);try {this.returnValueHandlers.handleReturnValue(returnValue, getReturnValueType(returnValue), mavContainer, webRequest);}catch (Exception ex) {if (logger.isTraceEnabled()) {logger.trace(formatErrorForReturnValue(returnValue), ex);}throw ex;}}InvocableHandlerMethod.invokeForRequest会调用InvocableHandlerMethod.doInvoke执行实际方法
public Object invokeForRequest(NativeWebRequest request, Nullable ModelAndViewContainer mavContainer,Object... providedArgs) throws Exception {Object[] args getMethodArgumentValues(request, mavContainer, providedArgs);if (logger.isTraceEnabled()) {logger.trace(Arguments: Arrays.toString(args));}return doInvoke(args);}InvocableHandlerMethod.doInvoke会调用实际的bean执行方法。从这一步的getBean()方法我们就能知道执行spring bean是什么类。
protected Object doInvoke(Object... args) throws Exception {Method method getBridgedMethod();try {if (KotlinDetector.isSuspendingFunction(method)) {return CoroutinesUtils.invokeSuspendingFunction(method, getBean(), args);}return method.invoke(getBean(), args);}catch (IllegalArgumentException ex) {assertTargetBean(method, getBean(), args);String text (ex.getMessage() ! null ? ex.getMessage() : Illegal argument);throw new IllegalStateException(formatInvokeError(text, args), ex);}catch (InvocationTargetException ex) {// Unwrap for HandlerExceptionResolvers ...Throwable targetException ex.getTargetException();if (targetException instanceof RuntimeException) {throw (RuntimeException) targetException;}else if (targetException instanceof Error) {throw (Error) targetException;}else if (targetException instanceof Exception) {throw (Exception) targetException;}else {throw new IllegalStateException(formatInvokeError(Invocation failure, args), targetException);}}}总结
上述源码调用流程如下
在深入研究Spring MVC的源码调用链路后有了以下体会
代码之间的调用关系错综复杂构成了一个深广交织的网络。通过阅读源码我们可以发现从请求的接收到处理再到响应的返回涉及了众多组件和层次的交互。这种深度的耦合使得没有全景图的情况下仅凭对各个类功能的碎片化认识难以形成对框架整体工作机制的实际理解。
为了真正掌握Spring MVC的内在逻辑后续工作需要着手细致地梳理这些类之间的组织结构明确它们如何协同工作以及各自的职责边界。这对于后续的框架使用、问题排查乃至自定义扩展都至关重要。
