SpringMVC具体执行流程
-
用户发送请求至前端控制器DispatcherServlet
-
DispatcherServlet收到请求调用处理器映射器HandlerMapping
处理器映射器根据请求url找到具体的处理器,生成处理器执行链HandlerExecutionChain(包括处理器对象和处理器拦截器)一并返回给DispatcherServlet -
DispatcherServlet根据处理器Handler获取处理器适配器
HandlerAdapter,执行HandlerAdapter处理一系列的操作,如:参数封装,数据格式转换,数据验证等操作 -
HandlerAdapter执行处理器Handler(Controller,也叫页面控制器)
Handler执行完成返回ModelAndView, 将执行结果ModelAndView返回到DispatcherServlet -
DispatcherServlet将ModelAndView传给ViewReslover视图解析器
ViewReslover解析后返回具体View -
DispatcherServlet对View进行渲染视图(即将模型数据model填充至视图中)
-
DispatcherServlet响应用户
一个URL请求执行流程
- 执行 HttpServlet 的 service(HttpServletRequest req, HttpServletResponse resp) 方法
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException
{
String method = req.getMethod();
if (method.equals(METHOD_GET)) {
long lastModified = getLastModified(req);
if (lastModified == -1) {
// servlet doesn't support if-modified-since, no reason
// to go through further expensive logic
doGet(req, resp);
} else {
long ifModifiedSince = req.getDateHeader(HEADER_IFMODSINCE);
if (ifModifiedSince < lastModified) {
// If the servlet mod time is later, call doGet()
// Round down to the nearest second for a proper compare
// A ifModifiedSince of -1 will always be less
maybeSetLastModified(resp, lastModified);
doGet(req, resp);
} else {
resp.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
}
}
} else if (method.equals(METHOD_HEAD)) {
long lastModified = getLastModified(req);
maybeSetLastModified(resp, lastModified);
doHead(req, resp);
} else if (method.equals(METHOD_POST)) {
doPost(req, resp);
} else if (method.equals(METHOD_PUT)) {
doPut(req, resp);
} else if (method.equals(METHOD_DELETE)) {
doDelete(req, resp);
} else if (method.equals(METHOD_OPTIONS)) {
doOptions(req,resp);
} else if (method.equals(METHOD_TRACE)) {
doTrace(req,resp);
} else {
//
// Note that this means NO servlet supports whatever
// method was requested, anywhere on this server.
//
String errMsg = lStrings.getString("http.method_not_implemented");
Object[] errArgs = new Object[1];
errArgs[0] = method;
errMsg = MessageFormat.format(errMsg, errArgs);
resp.sendError(HttpServletResponse.SC_NOT_IMPLEMENTED, errMsg);
}
}
- 执行demo请求 HttpServlet的doGet(HttpServletRequest req, HttpServletResponse resp)方法 子类 FrameworkServlet
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
process(request, response);
}
- FrameworkServlet的process方法
protected final void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
。。。。。。。
doService(request, response);
。。。。。。。
}
- FrameworkServlet 子类 DispatcherServlet 的doService(HttpServletRequest request, HttpServletResponse response)方法
protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
.......
doDispatch(request, response);
.......
}
- DispatcherServlet的doDispatch(HttpServletRequest request, HttpServletResponse response)方法 主方法(重点)
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 {
//文件上传相关
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request);
// DispatcherServlet收到请求调用处理器映射器HandlerMapping
// 处理器映射器根据请求url找到具体的处理器,生成处理器执行链HandlerExecutionChain(包括处理器对象和处理器拦截器)
// 并返回给DispatcherServlet
mappedHandler = getHandler(processedRequest);
if (mappedHandler == null) {
noHandlerFound(processedRequest, response);
return;
}
// DispatcherServlet根据处理器Handler获取处理器适配器HandlerAdapter
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
// Process last-modified header, if supported by the handler. HTTP缓存相关
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;
}
}
// 前置拦截器
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
// 返回false就不进行后续处理了
return;
}
// 执行HandlerAdapter处理一系列的操作,如:参数封装,数据格式转换,数据验证等操作
// 执行处理器Handler(Controller,也叫页面控制器)
// Handler执行完成返回ModelAndView
// HandlerAdapter将Handler执行结果ModelAndView返回到DispatcherServlet
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
if (asyncManager.isConcurrentHandlingStarted()) {
return;
}
// 如果没有视图,给你设置默认视图json忽略
applyDefaultViewName(processedRequest, mv);
//后置拦截器
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);
}
// DispatcherServlet将ModelAndView传给ViewReslover视图解析器
// ViewReslover解析后返回具体View
// DispatcherServlet对View进行渲染视图(即将模型数据model填充至视图中)
// DispatcherServlet响应用户
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);
}
}
}
}
默认的HandlerMapping根据URL匹配选择合适的
RequestMapping
HandlerMapping
SimpleUrlHandler
MappingBeanNameUrlHandlerMapping
默认的HandlerAdapter根据mappedHandler选择合适的
HttpRequestHandlerAdapter
SimpleControllerHandlerAdapter
RequestMappingHandlerAdapter
HandlerFunctionAdapter
@RequestMapping解析与请求映射
参考流程图: https://www.processon.com/view/link/615ea79e1efad4070b2d6707
执行处理器Handler
- 执行处理器Handler, 以RequestMappingHandlerAdapter为例
执行:
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
@Override
protected ModelAndView handleInternal(HttpServletRequest request,
HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
ModelAndView mav;
// 检查当前请求的method是否为支持的method(默认Null,可通过继承AbstractController设置supportedMethods)
// 检查当前请求是否必须session (默认false,可通过继承AbstractController设置requireSession)
checkRequest(request);
/**
* 判断当前是否需要支持在同一个session中只能线性地处理请求
* 因为锁是通过 synchronized 是 JVM 进程级,所以在分布式环境下,
* 无法达到同步相同 Session 的功能。默认情况下,synchronizeOnSession 为 false
*/
if (this.synchronizeOnSession) {
// 获取当前请求的session对象
HttpSession session = request.getSession(false);
if (session != null) {
// 为当前session生成一个唯一的可以用于锁定的key
Object mutex = WebUtils.getSessionMutex(session);
synchronized (mutex) {
// 对HandlerMethod进行参数等的适配处理,并调用目标handler
mav = invokeHandlerMethod(request, response, handlerMethod);
}
}
else {
// 如果当前不存在session,则直接对HandlerMethod进行适配
mav = invokeHandlerMethod(request, response, handlerMethod);
}
}
else {
// *如果当前不需要对session进行同步处理,则直接对HandlerMethod进行适配
mav = invokeHandlerMethod(request, response, handlerMethod);
}
//判断当前请求头中是否包含Cache-Control请求头,如果不包含,则对当前response进行处理
if (!response.containsHeader(HEADER_CACHE_CONTROL)) {
// 如果当前SessionAttribute中存在配置的attributes,则为其设置过期时间。
// 这里SessionAttribute主要是通过@SessionAttribute注解生成的
if (getSessionAttributesHandler(handlerMethod).hasSessionAttributes()) {
applyCacheSeconds(response, this.cacheSecondsForSessionAttributeHandlers);
}
else {
// 如果当前不存在SessionAttributes,则判断当前是否存在Cache-Control设置,
// 如果存在,则按照该设置进行response处理,如果不存在,则设置response中的
// Cache的过期时间为-1,即立即失效
prepareResponse(response);
}
}
return mav;
}
- 对HandlerMethod进行适配
@Nullable
protected ModelAndView invokeHandlerMethod(HttpServletRequest request,
HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
// 把我们的请求req resp包装成 ServletWebRequest
ServletWebRequest webRequest = new ServletWebRequest(request, response);
try {
// 获取容器中全局配置的InitBinder和当前HandlerMethod所对应的Controller中
// 配置的InitBinder,用于进行参数的绑定
WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod);
// 获取容器中全局配置的ModelAttribute和当前HandlerMethod所对应的Controller 中配置的ModelAttribute,
// 这些配置的方法将会在目标方法调用之前进行调用
ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory);
// 封装handlerMethod,会在调用前解析参数、调用后对返回值进行处理
ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod);
if (this.argumentResolvers != null) {
// 让invocableMethod拥有参数解析能力
invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
}
if (this.returnValueHandlers != null) {
// 让invocableMethod拥有返回值处理能力
invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);
}
// 让invocableMethod拥有InitBinder解析能力
invocableMethod.setDataBinderFactory(binderFactory);
// 设置ParameterNameDiscoverer,该对象将按照一定的规则获取当前参数的名称
invocableMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);
// ModelAndView处理容器
ModelAndViewContainer mavContainer = new ModelAndViewContainer();
// 将request的Attribute复制一份到ModelMap
mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));
// *调用我们标注了@ModelAttribute的方法,主要是为我们的目标方法预加载
modelFactory.initModel(webRequest, mavContainer, invocableMethod);
// 重定向的时候,忽略model中的数据 默认false
mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect);
// 获取当前的AsyncWebRequest,这里AsyncWebRequest的主要作用是用于判断目标
// handler的返回值是否为WebAsyncTask或DeferredResult,如果是这两种中的一种,
// 则说明当前请求的处理应该是异步的。所谓的异步,指的是当前请求会将Controller中
// 封装的业务逻辑放到一个线程池中进行调用,待该调用有返回结果之后再返回到response中。
// 这种处理的优点在于用于请求分发的线程能够解放出来,从而处理更多的请求,提高吞吐。
// 只有待目标任务完成之后才会回来将该异步任务的结果返回。
AsyncWebRequest asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(request, response);
asyncWebRequest.setTimeout(this.asyncRequestTimeout);
// 封装异步任务的线程池、request、interceptors到WebAsyncManager中
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
asyncManager.setTaskExecutor(this.taskExecutor);
asyncManager.setAsyncWebRequest(asyncWebRequest);
asyncManager.registerCallableInterceptors(this.callableInterceptors);
asyncManager.registerDeferredResultInterceptors(this.deferredResultInterceptors);
// 这里就是用于判断当前请求是否有异步任务结果的,如果存在,则对异步任务结果进行封装
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);
}
// *对请求参数进行处理,调用目标HandlerMethod,并且将返回值封装为一个ModelAndView对象
invocableMethod.invokeAndHandle(webRequest, mavContainer);
if (asyncManager.isConcurrentHandlingStarted()) {
return null;
}
// 对封装的ModelAndView进行处理,主要是判断当前请求是否进行了重定向,如果进行了重定向,
// 还会判断是否需要将FlashAttributes封装到新的请求中
return getModelAndView(mavContainer, modelFactory, webRequest);
}
finally {
webRequest.requestCompleted();
}
}
- 对请求参数进行处理,调用目标HandlerMethod,并且将返回值封装为一个ModelAndView对象 ServletInvocableHandlerMethod
invocableMethod.invokeAndHandle(webRequest, mavContainer)
public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception {
/*真正的调用我们的目标对象 很重要 很重要*/
Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);
// 设置相关的返回状态
setResponseStatus(webRequest);
// 如果请求处理完成,则设置requestHandled属性
if (returnValue == null) {
if (isRequestNotModified(webRequest) || getResponseStatus() != null || mavContainer.isRequestHandled()) {
disableContentCachingIfNecessary(webRequest);
mavContainer.setRequestHandled(true);
return;
}
}
// 如果请求失败,但是有错误原因,那么也会设置requestHandled属性
else if (StringUtils.hasText(getResponseStatusReason())) {
mavContainer.setRequestHandled(true);
return;
}
mavContainer.setRequestHandled(false);
Assert.state(this.returnValueHandlers != null, "No return value handlers");
try {
// 遍历当前容器中所有ReturnValueHandler,判断哪种handler支持当前返回值的处理,
// 如果支持,则使用该handler处理该返回值
this.returnValueHandlers.handleReturnValue(
returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
}
catch (Exception ex) {
if (logger.isTraceEnabled()) {
logger.trace(formatErrorForReturnValue(returnValue), ex);
}
throw ex;
}
}
- 真正的调用我们的目标对象 很重要 很重要
Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);
@Nullable
public Object invokeForRequest(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception {
//*获取我们目标方法入参的值
Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);
if (logger.isTraceEnabled()) {
logger.trace("Arguments: " + Arrays.toString(args));
}
//真的的调用我们的目标方法
return doInvoke(args);
}
doInvoke(args) 反射调用