SpringWeb 拦截器(spring中拦截器)

  本篇文章为你整理了SpringWeb 拦截器(spring中拦截器)的详细内容,包含有springweb拦截器登录 spring中拦截器 拦截器springmvc springboot web拦截器 SpringWeb 拦截器,希望能帮助你了解 SpringWeb 拦截器。

  spring拦截器能帮我们实现验证是否登陆、验签校验请求是否合法、预先设置数据等功能,那么该如何设置拦截器以及它的原理如何呢,下面将进行简单的介绍

  HandlerInterceptor接口

  

public interface HandlerInterceptor {

 

   * Intercept the execution of a handler. Called after HandlerMapping determined

   * an appropriate handler object, but before HandlerAdapter invokes the handler.

   * p DispatcherServlet processes a handler in an execution chain, consisting

   * of any number of interceptors, with the handler itself at the end.

   * With this method, each interceptor can decide to abort the execution chain,

   * typically sending a HTTP error or writing a custom response.

   * p strong Note: /strong special considerations apply for asynchronous

   * request processing. For more details see

   * {@link org.springframework.web.servlet.AsyncHandlerInterceptor}.

   * p The default implementation returns {@code true}.

   * @param request current HTTP request

   * @param response current HTTP response

   * @param handler chosen handler to execute, for type and/or instance evaluation

   * @return {@code true} if the execution chain should proceed with the

   * next interceptor or the handler itself. Else, DispatcherServlet assumes

   * that this interceptor has already dealt with the response itself.

   * @throws Exception in case of errors

   default boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)

   throws Exception {

   return true;

   * Intercept the execution of a handler. Called after HandlerAdapter actually

   * invoked the handler, but before the DispatcherServlet renders the view.

   * Can expose additional model objects to the view via the given ModelAndView.

   * p DispatcherServlet processes a handler in an execution chain, consisting

   * of any number of interceptors, with the handler itself at the end.

   * With this method, each interceptor can post-process an execution,

   * getting applied in inverse order of the execution chain.

   * p strong Note: /strong special considerations apply for asynchronous

   * request processing. For more details see

   * {@link org.springframework.web.servlet.AsyncHandlerInterceptor}.

   * p The default implementation is empty.

   * @param request current HTTP request

   * @param response current HTTP response

   * @param handler handler (or {@link HandlerMethod}) that started asynchronous

   * execution, for type and/or instance examination

   * @param modelAndView the {@code ModelAndView} that the handler returned

   * (can also be {@code null})

   * @throws Exception in case of errors

   default void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,

   @Nullable ModelAndView modelAndView) throws Exception {

   * Callback after completion of request processing, that is, after rendering

   * the view. Will be called on any outcome of handler execution, thus allows

   * for proper resource cleanup.

   * p Note: Will only be called if this interceptors {@code preHandle}

   * method has successfully completed and returned {@code true}!

   * p As with the {@code postHandle} method, the method will be invoked on each

   * interceptor in the chain in reverse order, so the first interceptor will be

   * the last to be invoked.

   * p strong Note: /strong special considerations apply for asynchronous

   * request processing. For more details see

   * {@link org.springframework.web.servlet.AsyncHandlerInterceptor}.

   * p The default implementation is empty.

   * @param request current HTTP request

   * @param response current HTTP response

   * @param handler handler (or {@link HandlerMethod}) that started asynchronous

   * execution, for type and/or instance examination

   * @param ex exception thrown on handler execution, if any

   * @throws Exception in case of errors

   default void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler,

   @Nullable Exception ex) throws Exception {

  }

 

  自定义拦截器需要实现HandlerInteceptor接口,该接口有三个方法:

  preHandle:主要在映射适配器执行handler之前调用,若返回为true则继续往下执行handler,若返回为false则直接返回不继续处理请求

  postHandle:主要在适配器执行handler之后调用

  afterCompletion:在postHandle后调用可清理一些数据,若preHandle返回false那么会调用完此方法后再返回

  

@Component

 

  @Slf4j(topic = "e")

  public class CustomInterceptor implements HandlerInterceptor {

   @Override

   public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)

   throws Exception {

   log.info("-------------拦截请求:" + request.getRequestURI() + "-------------");

   // 可以根据request设置请求头、或从请求头提取信息等等...

   return true;

   @Override

   public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,

   @Nullable ModelAndView modelAndView) throws Exception {

   log.info("postHandle ....");

   @Override

   public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler,

   @Nullable Exception ex) throws Exception {

   log.info("afterCompletion ....");

  }

 

  接着创建配置类,实现WebMvcConfigurer接口,重写addInterceptors方法将自定义拦截器添加,并且加上@EnableWebMvc注解 (springboot项目会自动配置)

  

@Configuration

 

  @EnableWebMvc

  public class MyMvcConfigurer implements WebMvcConfigurer {

   @Resource

   private CustomInterceptor customInterceptor;

   @Override

   public void addInterceptors(InterceptorRegistry registry) {

   registry.addInterceptor(customInterceptor)

   .addPathPatterns("/**");

  }

 

  配置完之后启动项目访问某个url路径,从控制台可以看到拦截器确实生效了

  

  首先是@EnableWebMvc注解,spring会解析并导入DelegatingWebMvcConfiguration这个bean,继承关系如下,主要逻辑都写在父类WebMvcConfigurationSupport中

  

@Retention(RetentionPolicy.RUNTIME)

 

  @Target(ElementType.TYPE)

  @Documented

  @Import(DelegatingWebMvcConfiguration.class)

  public @interface EnableWebMvc {

  }

 

  WebMvcConfigurationSupport中会创建一个映射处理器RequestMappingHandlerMapping

  

@Bean

 

  public RequestMappingHandlerMapping requestMappingHandlerMapping() {

   RequestMappingHandlerMapping mapping = createRequestMappingHandlerMapping();

   mapping.setOrder(0);

   // 设置拦截器到mapping

   mapping.setInterceptors(getInterceptors());

   // 设置内容协商管理器

   mapping.setContentNegotiationManager(mvcContentNegotiationManager());

   // 跨域配置

   mapping.setCorsConfigurations(getCorsConfigurations());

   // 路径匹配设置

   PathMatchConfigurer configurer = getPathMatchConfigurer();

   Boolean useSuffixPatternMatch = configurer.isUseSuffixPatternMatch();

   if (useSuffixPatternMatch != null) {

   mapping.setUseSuffixPatternMatch(useSuffixPatternMatch);

   Boolean useRegisteredSuffixPatternMatch = configurer.isUseRegisteredSuffixPatternMatch();

   if (useRegisteredSuffixPatternMatch != null) {

   mapping.setUseRegisteredSuffixPatternMatch(useRegisteredSuffixPatternMatch);

   Boolean useTrailingSlashMatch = configurer.isUseTrailingSlashMatch();

   if (useTrailingSlashMatch != null) {

   mapping.setUseTrailingSlashMatch(useTrailingSlashMatch);

   UrlPathHelper pathHelper = configurer.getUrlPathHelper();

   if (pathHelper != null) {

   mapping.setUrlPathHelper(pathHelper);

   PathMatcher pathMatcher = configurer.getPathMatcher();

   if (pathMatcher != null) {

   mapping.setPathMatcher(pathMatcher);

   return mapping;

  
if (this.interceptors == null) {

   InterceptorRegistry registry = new InterceptorRegistry();

   // 调用DelegatingWebMvcConfiguration.addInterceptors 添加自定义的拦截器

   addInterceptors(registry);

   registry.addInterceptor(new ConversionServiceExposingInterceptor(mvcConversionService()));

   registry.addInterceptor(new ResourceUrlProviderExposingInterceptor(mvcResourceUrlProvider()));

   // 获取拦截器并根据order排序,若有匹配路径则封装成MappedInterceptor

   this.interceptors = registry.getInterceptors();

   return this.interceptors.toArray();

  }

 

  注意这一行代码mapping.setInterceptors(getInterceptors()); getInterceptors方法会调用子类DelegatingWebMvcConfiguration的addInterceptors方法,接着会调用委托类即我们自定义配置类MyMvcConfigurer类的addInterceptors方法,将自定义的拦截器添加到拦截器注册类中,而后通过拦截器注册类获取到拦截器列表,最后将拦截器添加到映射处理器handlerMapping中,供后续使用。

  最后看下请求处理的DispatcherServlet#doDispatch方法 (为了看的更清楚一点删掉了一些代码)

  

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

 

   HttpServletRequest processedRequest = request;

   // 处理程序执行链

   HandlerExecutionChain mappedHandler = null;

   try {

   ModelAndView mv = null;

   Exception dispatchException = null;

   try {

   // Determine handler for the current request.

   // 遍历handlerMapping获取能处理request的处理器,mappedHandler里封装着之前我们定义的拦截器供后续调用

   mappedHandler = getHandler(processedRequest);

   if (mappedHandler == null) {

   noHandlerFound(processedRequest, response);

   return;

   // Determine handler adapter for the current request.

   // 确定处理当前请求的处理适配器 RequestMappingHandlerAdapter

   HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

   // 执行handler之前应用拦截器执行拦截器的后置方法 返回为false表示请求不合理直接返回了

   if (!mappedHandler.applyPreHandle(processedRequest, response)) {

   return;

   // Actually invoke the handler.

   // 真正执行这个HandlerMethod

   mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

   applyDefaultViewName(processedRequest, mv);

   // 执行拦截器的后置方法

   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);

   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 {

  
#mappedHandler.applyPreHandle

  boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {

   HandlerInterceptor[] interceptors = getInterceptors();

   if (!ObjectUtils.isEmpty(interceptors)) {

   for (int i = 0; i interceptors.length; i++) {

   HandlerInterceptor interceptor = interceptors[i];

   // 前置处理为false时

   if (!interceptor.preHandle(request, response, this.handler)) {

   // 触发拦截器的afterCompletion方法

   triggerAfterCompletion(request, response, null);

   return false;

   this.interceptorIndex = i;

   return true;

  }

 

  可以看到再真正执行handler之前会调用mappedHandler.applyPreHandle 方法,遍历拦截器执行preHandle方法,若返回false则根据先前执行过的拦截器顺序倒序执行afterCompletion方法,都通过的话后续执行handler获取请求结果,再接着执行拦截器的postHandle方法最后执行afterCompletion方法。

  以上就是SpringWeb 拦截器(spring中拦截器)的详细内容,想要了解更多 SpringWeb 拦截器的内容,请持续关注盛行IT软件开发工作室。

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