建站公司跑路了域名怎么办,深圳网络营销网站建设,镇江市建设工程招投标网站,哪些网站做翻译可以赚钱十、拦截器
1、拦截器的配置
SpringMVC中的拦截器用于拦截控制器方法的执行
SpringMVC中的拦截器需要实现HandlerInterceptor
SpringMVC的拦截器必须在SpringMVC的配置文件中进行配置#xff1a;
bean classcom.atguigu.interceptor.FirstInterceptor
bean classcom.atguigu.interceptor.FirstInterceptor/bean
ref beanfirstInterceptor/ref
!-- 以上两种配置方式都是对DispatcherServlet所处理的所有的请求进行拦截 --
mvc:interceptormvc:mapping path/**/mvc:exclude-mapping path/testRequestEntity/ref beanfirstInterceptor/ref
/mvc:interceptor
!-- 以上配置方式可以通过ref或bean标签设置拦截器通过mvc:mapping设置需要拦截的请求通过mvc:exclude-mapping设置需要排除的请求即不需要拦截的请求
--2、拦截器的三个抽象方法
SpringMVC中的拦截器有三个抽象方法
preHandle控制器方法执行之前执行preHandle()其boolean类型的返回值表示是否拦截或放行返回true为放行即调用控制器方法返回false表示拦截即不调用控制器方法
postHandle控制器方法执行之后执行postHandle()
afterComplation处理完视图和模型数据渲染视图完毕之后执行afterComplation()
3、多个拦截器的执行顺序
a若每个拦截器的preHandle()都返回true
此时多个拦截器的执行顺序和拦截器在SpringMVC的配置文件的配置顺序有关
preHandle()会按照配置的顺序执行而postHandle()和afterComplation()会按照配置的反序执行
b若某个拦截器的preHandle()返回了false
preHandle()返回false和它之前的拦截器的preHandle()都会执行postHandle()都不执行返回false的拦截器之前的拦截器的afterComplation()会执行
十一、异常处理器
1、基于配置的异常处理
SpringMVC提供了一个处理控制器方法执行过程中所出现的异常的接口HandlerExceptionResolver
HandlerExceptionResolver接口的实现类有DefaultHandlerExceptionResolver和SimpleMappingExceptionResolver
SpringMVC提供了自定义的异常处理器SimpleMappingExceptionResolver使用方式
bean classorg.springframework.web.servlet.handler.SimpleMappingExceptionResolverproperty nameexceptionMappingsprops!--properties的键表示处理器方法执行过程中出现的异常properties的值表示若出现指定异常时设置一个新的视图名称跳转到指定页面--prop keyjava.lang.ArithmeticExceptionerror/prop/props/property!--exceptionAttribute属性设置一个属性名将出现的异常信息在请求域中进行共享--property nameexceptionAttribute valueex/property
/bean2、基于注解的异常处理
//ControllerAdvice将当前类标识为异常处理的组件
ControllerAdvice
public class ExceptionController {//ExceptionHandler用于设置所标识方法处理的异常ExceptionHandler(ArithmeticException.class)//ex表示当前请求处理中出现的异常对象public String handleArithmeticException(Exception ex, Model model){model.addAttribute(ex, ex);return error;}}十二、注解配置SpringMVC
使用配置类和注解代替web.xml和SpringMVC配置文件的功能
1、创建初始化类代替web.xml
在Servlet3.0环境中容器会在类路径中查找实现javax.servlet.ServletContainerInitializer接口的类如果找到的话就用它来配置Servlet容器。 Spring提供了这个接口的实现名为SpringServletContainerInitializer这个类反过来又会查找实现WebApplicationInitializer的类并将配置的任务交给它们来完成。Spring3.2引入了一个便利的WebApplicationInitializer基础实现名为AbstractAnnotationConfigDispatcherServletInitializer当我们的类扩展了AbstractAnnotationConfigDispatcherServletInitializer并将其部署到Servlet3.0容器的时候容器会自动发现它并用它来配置Servlet上下文。
public class WebInit extends AbstractAnnotationConfigDispatcherServletInitializer {/*** 指定spring的配置类* return*/Overrideprotected Class?[] getRootConfigClasses() {return new Class[]{SpringConfig.class};}/*** 指定SpringMVC的配置类* return*/Overrideprotected Class?[] getServletConfigClasses() {return new Class[]{WebConfig.class};}/*** 指定DispatcherServlet的映射规则即url-pattern* return*/Overrideprotected String[] getServletMappings() {return new String[]{/};}/*** 添加过滤器* return*/Overrideprotected Filter[] getServletFilters() {CharacterEncodingFilter encodingFilter new CharacterEncodingFilter();encodingFilter.setEncoding(UTF-8);encodingFilter.setForceRequestEncoding(true);HiddenHttpMethodFilter hiddenHttpMethodFilter new HiddenHttpMethodFilter();return new Filter[]{encodingFilter, hiddenHttpMethodFilter};}
}2、创建SpringConfig配置类代替spring的配置文件
Configuration
public class SpringConfig {//ssm整合之后spring的配置信息写在此类中
}3、创建WebConfig配置类代替SpringMVC的配置文件
Configuration
//扫描组件
ComponentScan(com.atguigu.mvc.controller)
//开启MVC注解驱动
EnableWebMvc
public class WebConfig implements WebMvcConfigurer {//使用默认的servlet处理静态资源Overridepublic void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {configurer.enable();}//配置文件上传解析器Beanpublic CommonsMultipartResolver multipartResolver(){return new CommonsMultipartResolver();}//配置拦截器Overridepublic void addInterceptors(InterceptorRegistry registry) {FirstInterceptor firstInterceptor new FirstInterceptor();registry.addInterceptor(firstInterceptor).addPathPatterns(/**);}//配置视图控制/*Overridepublic void addViewControllers(ViewControllerRegistry registry) {registry.addViewController(/).setViewName(index);}*///配置异常映射/*Overridepublic void configureHandlerExceptionResolvers(ListHandlerExceptionResolver resolvers) {SimpleMappingExceptionResolver exceptionResolver new SimpleMappingExceptionResolver();Properties prop new Properties();prop.setProperty(java.lang.ArithmeticException, error);//设置异常映射exceptionResolver.setExceptionMappings(prop);//设置共享异常信息的键exceptionResolver.setExceptionAttribute(ex);resolvers.add(exceptionResolver);}*///配置生成模板解析器Beanpublic ITemplateResolver templateResolver() {WebApplicationContext webApplicationContext ContextLoader.getCurrentWebApplicationContext();// ServletContextTemplateResolver需要一个ServletContext作为构造参数可通过WebApplicationContext 的方法获得ServletContextTemplateResolver templateResolver new ServletContextTemplateResolver(webApplicationContext.getServletContext());templateResolver.setPrefix(/WEB-INF/templates/);templateResolver.setSuffix(.html);templateResolver.setCharacterEncoding(UTF-8);templateResolver.setTemplateMode(TemplateMode.HTML);return templateResolver;}//生成模板引擎并为模板引擎注入模板解析器Beanpublic SpringTemplateEngine templateEngine(ITemplateResolver templateResolver) {SpringTemplateEngine templateEngine new SpringTemplateEngine();templateEngine.setTemplateResolver(templateResolver);return templateEngine;}//生成视图解析器并未解析器注入模板引擎Beanpublic ViewResolver viewResolver(SpringTemplateEngine templateEngine) {ThymeleafViewResolver viewResolver new ThymeleafViewResolver();viewResolver.setCharacterEncoding(UTF-8);viewResolver.setTemplateEngine(templateEngine);return viewResolver;}}4、测试功能
RequestMapping(/)
public String index(){return index;
}十三、SpringMVC执行流程
1、SpringMVC常用组件
DispatcherServlet前端控制器不需要工程师开发由框架提供
作用统一处理请求和响应整个流程控制的中心由它调用其它组件处理用户的请求
HandlerMapping处理器映射器不需要工程师开发由框架提供
作用根据请求的url、method等信息查找Handler即控制器方法
Handler处理器需要工程师开发
作用在DispatcherServlet的控制下Handler对具体的用户请求进行处理
HandlerAdapter处理器适配器不需要工程师开发由框架提供
作用通过HandlerAdapter对处理器控制器方法进行执行
ViewResolver视图解析器不需要工程师开发由框架提供
作用进行视图解析得到相应的视图例如ThymeleafView、InternalResourceView、RedirectView
View视图
作用将模型数据通过页面展示给用户
2、DispatcherServlet初始化过程
DispatcherServlet 本质上是一个 Servlet所以天然的遵循 Servlet 的生命周期。所以宏观上是 Servlet 生命周期来进行调度。 a初始化WebApplicationContext
所在类org.springframework.web.servlet.FrameworkServlet
protected WebApplicationContext initWebApplicationContext() {WebApplicationContext rootContext WebApplicationContextUtils.getWebApplicationContext(getServletContext());WebApplicationContext wac null;if (this.webApplicationContext ! null) {// A context instance was injected at construction time - use itwac this.webApplicationContext;if (wac instanceof ConfigurableWebApplicationContext) {ConfigurableWebApplicationContext cwac (ConfigurableWebApplicationContext) wac;if (!cwac.isActive()) {// The context has not yet been refreshed - provide services such as// setting the parent context, setting the application context id, etcif (cwac.getParent() null) {// The context instance was injected without an explicit parent - set// the root application context (if any; may be null) as the parentcwac.setParent(rootContext);}configureAndRefreshWebApplicationContext(cwac);}}}if (wac null) {// No context instance was injected at construction time - see if one// has been registered in the servlet context. If one exists, it is assumed// that the parent context (if any) has already been set and that the// user has performed any initialization such as setting the context idwac findWebApplicationContext();}if (wac null) {// No context instance is defined for this servlet - create a local one// 创建WebApplicationContextwac createWebApplicationContext(rootContext);}if (!this.refreshEventReceived) {// Either the context is not a ConfigurableApplicationContext with refresh// support or the context injected at construction time had already been// refreshed - trigger initial onRefresh manually here.synchronized (this.onRefreshMonitor) {// 刷新WebApplicationContextonRefresh(wac);}}if (this.publishContext) {// Publish the context as a servlet context attribute.// 将IOC容器在应用域共享String attrName getServletContextAttributeName();getServletContext().setAttribute(attrName, wac);}return wac;
}b创建WebApplicationContext
所在类org.springframework.web.servlet.FrameworkServlet
protected WebApplicationContext createWebApplicationContext(Nullable ApplicationContext parent) {Class? contextClass getContextClass();if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {throw new ApplicationContextException(Fatal initialization error in servlet with name getServletName() : custom WebApplicationContext class [ contextClass.getName() ] is not of type ConfigurableWebApplicationContext);}// 通过反射创建 IOC 容器对象ConfigurableWebApplicationContext wac (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);wac.setEnvironment(getEnvironment());// 设置父容器wac.setParent(parent);String configLocation getContextConfigLocation();if (configLocation ! null) {wac.setConfigLocation(configLocation);}configureAndRefreshWebApplicationContext(wac);return wac;
}cDispatcherServlet初始化策略
FrameworkServlet创建WebApplicationContext后刷新容器调用onRefresh(wac)此方法在DispatcherServlet中进行了重写调用了initStrategies(context)方法初始化策略即初始化DispatcherServlet的各个组件
所在类org.springframework.web.servlet.DispatcherServlet
protected void initStrategies(ApplicationContext context) {initMultipartResolver(context);initLocaleResolver(context);initThemeResolver(context);initHandlerMappings(context);initHandlerAdapters(context);initHandlerExceptionResolvers(context);initRequestToViewNameTranslator(context);initViewResolvers(context);initFlashMapManager(context);
}3、DispatcherServlet调用组件处理请求
aprocessRequest()
FrameworkServlet重写HttpServlet中的service()和doXxx()这些方法中调用了processRequest(request, response)
所在类org.springframework.web.servlet.FrameworkServlet
protected final void processRequest(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {long startTime System.currentTimeMillis();Throwable failureCause null;LocaleContext previousLocaleContext LocaleContextHolder.getLocaleContext();LocaleContext localeContext buildLocaleContext(request);RequestAttributes previousAttributes RequestContextHolder.getRequestAttributes();ServletRequestAttributes requestAttributes buildRequestAttributes(request, response, previousAttributes);WebAsyncManager asyncManager WebAsyncUtils.getAsyncManager(request);asyncManager.registerCallableInterceptor(FrameworkServlet.class.getName(), new RequestBindingInterceptor());initContextHolders(request, localeContext, requestAttributes);try {// 执行服务doService()是一个抽象方法在DispatcherServlet中进行了重写doService(request, response);}catch (ServletException | IOException ex) {failureCause ex;throw ex;}catch (Throwable ex) {failureCause ex;throw new NestedServletException(Request processing failed, ex);}finally {resetContextHolders(request, previousLocaleContext, previousAttributes);if (requestAttributes ! null) {requestAttributes.requestCompleted();}logResult(request, response, failureCause, asyncManager);publishRequestHandledEvent(request, response, startTime, failureCause);}
}bdoService()
所在类org.springframework.web.servlet.DispatcherServlet
Override
protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {logRequest(request);// Keep a snapshot of the request attributes in case of an include,// to be able to restore the original attributes after the include.MapString, Object attributesSnapshot null;if (WebUtils.isIncludeRequest(request)) {attributesSnapshot new HashMap();Enumeration? attrNames request.getAttributeNames();while (attrNames.hasMoreElements()) {String attrName (String) attrNames.nextElement();if (this.cleanupAfterInclude || attrName.startsWith(DEFAULT_STRATEGIES_PREFIX)) {attributesSnapshot.put(attrName, request.getAttribute(attrName));}}}// Make framework objects available to handlers and view objects.request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, getWebApplicationContext());request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver);request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver);request.setAttribute(THEME_SOURCE_ATTRIBUTE, getThemeSource());if (this.flashMapManager ! null) {FlashMap inputFlashMap this.flashMapManager.retrieveAndUpdate(request, response);if (inputFlashMap ! null) {request.setAttribute(INPUT_FLASH_MAP_ATTRIBUTE, Collections.unmodifiableMap(inputFlashMap));}request.setAttribute(OUTPUT_FLASH_MAP_ATTRIBUTE, new FlashMap());request.setAttribute(FLASH_MAP_MANAGER_ATTRIBUTE, this.flashMapManager);}RequestPath requestPath null;if (this.parseRequestPath !ServletRequestPathUtils.hasParsedRequestPath(request)) {requestPath ServletRequestPathUtils.parseAndCache(request);}try {// 处理请求和响应doDispatch(request, response);}finally {if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {// Restore the original attribute snapshot, in case of an include.if (attributesSnapshot ! null) {restoreAttributesAfterInclude(request, attributesSnapshot);}}if (requestPath ! null) {ServletRequestPathUtils.clearParsedRequestPath(request);}}
}cdoDispatch()
所在类org.springframework.web.servlet.DispatcherServlet
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调用链包含handler、interceptorList、interceptorIndexhandler浏览器发送的请求所匹配的控制器方法interceptorList处理控制器方法的所有拦截器集合interceptorIndex拦截器索引控制拦截器afterCompletion()的执行*/mappedHandler getHandler(processedRequest);if (mappedHandler null) {noHandlerFound(processedRequest, response);return;}// Determine handler adapter for the current request.// 通过控制器方法创建相应的处理器适配器调用所对应的控制器方法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 (new ServletWebRequest(request, response).checkNotModified(lastModified) isGet) {return;}}// 调用拦截器的preHandle()if (!mappedHandler.applyPreHandle(processedRequest, response)) {return;}// Actually invoke the handler.// 由处理器适配器调用具体的控制器方法最终获得ModelAndView对象mv ha.handle(processedRequest, response, mappedHandler.getHandler());if (asyncManager.isConcurrentHandlingStarted()) {return;}applyDefaultViewName(processedRequest, mv);// 调用拦截器的postHandle()mappedHandler.applyPostHandle(processedRequest, response, mv);}catch (Exception ex) {dispatchException ex;}catch (Throwable err) {// As of 4.3, were processing Errors thrown from handler methods as well,// making them available for ExceptionHandler methods and other scenarios.dispatchException new NestedServletException(Handler dispatch failed, err);}// 后续处理处理模型数据和渲染视图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 afterCompletionif (mappedHandler ! null) {mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);}}else {// Clean up any resources used by a multipart request.if (multipartRequestParsed) {cleanupMultipart(processedRequest);}}}
}dprocessDispatchResult()
private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,Nullable HandlerExecutionChain mappedHandler, Nullable ModelAndView mv,Nullable Exception exception) throws Exception {boolean errorView false;if (exception ! null) {if (exception instanceof ModelAndViewDefiningException) {logger.debug(ModelAndViewDefiningException encountered, exception);mv ((ModelAndViewDefiningException) exception).getModelAndView();}else {Object handler (mappedHandler ! null ? mappedHandler.getHandler() : null);mv processHandlerException(request, response, handler, exception);errorView (mv ! null);}}// Did the handler return a view to render?if (mv ! null !mv.wasCleared()) {// 处理模型数据和渲染视图render(mv, request, response);if (errorView) {WebUtils.clearErrorRequestAttributes(request);}}else {if (logger.isTraceEnabled()) {logger.trace(No view rendering, null ModelAndView returned.);}}if (WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {// Concurrent handling started during a forwardreturn;}if (mappedHandler ! null) {// Exception (if any) is already handled..// 调用拦截器的afterCompletion()mappedHandler.triggerAfterCompletion(request, response, null);}
}4、SpringMVC的执行流程 用户向服务器发送请求请求被SpringMVC 前端控制器 DispatcherServlet捕获。 DispatcherServlet对请求URL进行解析得到请求资源标识符URI判断请求URI对应的映射
a) 不存在
i. 再判断是否配置了mvc:default-servlet-handler
ii. 如果没配置则控制台报映射查找不到客户端展示404错误 iii. 如果有配置则访问目标资源一般为静态资源如JS,CSS,HTML找不到客户端也会展示404错误 b) 存在则执行下面的流程 根据该URI调用HandlerMapping获得该Handler配置的所有相关的对象包括Handler对象以及Handler对象对应的拦截器最后以HandlerExecutionChain执行链对象的形式返回。 DispatcherServlet 根据获得的Handler选择一个合适的HandlerAdapter。 如果成功获得HandlerAdapter此时将开始执行拦截器的preHandler(…)方法【正向】 提取Request中的模型数据填充Handler入参开始执行HandlerController)方法处理请求。在填充Handler的入参过程中根据你的配置Spring将帮你做一些额外的工作
a) HttpMessageConveter 将请求消息如Json、xml等数据转换成一个对象将对象转换为指定的响应信息
b) 数据转换对请求消息进行数据转换。如String转换成Integer、Double等
c) 数据格式化对请求消息进行数据格式化。 如将字符串转换成格式化数字或格式化日期等
d) 数据验证 验证数据的有效性长度、格式等验证结果存储到BindingResult或Error中 Handler执行完成后向DispatcherServlet 返回一个ModelAndView对象。 此时将开始执行拦截器的postHandle(…)方法【逆向】。 根据返回的ModelAndView此时会判断是否存在异常如果存在异常则执行HandlerExceptionResolver进行异常处理选择一个适合的ViewResolver进行视图解析根据Model和View来渲染视图。 渲染视图完毕执行拦截器的afterCompletion(…)方法【逆向】。 将渲染结果返回给客户端。
