概述

这是一个Spring MVC助手类，用于集合应用所配置的HandlerMapping(url pattern和请求处理handler之间的映射)表，用于获取针对某个请求的如下信息 :

getMatchableHandlerMapping(javax.servlet.http.HttpServletRequest)

寻找能处理指定请求的HandlerMapping，如果找不到，返回null;如果找到的是一个MatchableHandlerMapping，则返回；如果找得到当并不是MatchableHandlerMapping，则抛出异常IllegalStateException。
getCorsConfiguration(javax.servlet.http.HttpServletRequest)

获取针对指定请求的CORS配置，封装为CorsConfiguration。如果不存在相应配置，返回null。

使用

作为CorsConfigurationSource使用

    // 配置类 WebMvcConfigurationSupport@Bean@Lazypublic HandlerMappingIntrospector mvcHandlerMappingIntrospector() {return new HandlerMappingIntrospector();}

源代码

源代码版本 Spring Web MVC 5.1.5.RELEASE


package org.springframework.web.servlet.handler;// 省略 importspublic class HandlerMappingIntrospectorimplements CorsConfigurationSource, ApplicationContextAware, InitializingBean {@Nullableprivate ApplicationContext applicationContext;@Nullableprivate List<HandlerMapping> handlerMappings;/*** Constructor for use with ApplicationContextAware.*/public HandlerMappingIntrospector() {}/*** Constructor that detects the configured {@code HandlerMapping}s in the* given {@code ApplicationContext} or falls back on* "DispatcherServlet.properties" like the {@code DispatcherServlet}.* @deprecated as of 4.3.12, in favor of {@link #setApplicationContext}*/@Deprecatedpublic HandlerMappingIntrospector(ApplicationContext context) {this.handlerMappings = initHandlerMappings(context);}/*** Return the configured HandlerMapping's.*/public List<HandlerMapping> getHandlerMappings() {return (this.handlerMappings != null ? this.handlerMappings : Collections.emptyList());}@Overridepublic void setApplicationContext(ApplicationContext applicationContext) {this.applicationContext = applicationContext;}// InitializingBean 接口约定的方法，用于获取容器中定义的所有类型为 HandlerMapping 的 bean,// 或者获取缺省定义的类型为 HandlerMapping 的 bean@Overridepublic void afterPropertiesSet() {if (this.handlerMappings == null) {Assert.notNull(this.applicationContext, "No ApplicationContext");this.handlerMappings = initHandlerMappings(this.applicationContext);}}/*** Find the {@link HandlerMapping} that would handle the given request and* return it as a {@link MatchableHandlerMapping} that can be used to test* request-matching criteria.* <p>If the matching HandlerMapping is not an instance of* {@link MatchableHandlerMapping}, an IllegalStateException is raised.* @param request the current request* @return the resolved matcher, or {@code null}* @throws Exception if any of the HandlerMapping's raise an exception*/@Nullablepublic MatchableHandlerMapping getMatchableHandlerMapping(HttpServletRequest request) throws Exception {Assert.notNull(this.handlerMappings, "Handler mappings not initialized");HttpServletRequest wrapper = new RequestAttributeChangeIgnoringWrapper(request);for (HandlerMapping handlerMapping : this.handlerMappings) {Object handler = handlerMapping.getHandler(wrapper);if (handler == null) {continue;}if (handlerMapping instanceof MatchableHandlerMapping) {return ((MatchableHandlerMapping) handlerMapping);}throw new IllegalStateException("HandlerMapping is not a MatchableHandlerMapping");}return null;}// 获取某个 request 请求对应的 CorsConfiguration// 1. 从 handlerMappings 中找到该请求对应的 handler, 形式为 HandlerExecutionChain;// 2. 检索 HandlerExecutionChain 中所有的 @Override@Nullablepublic CorsConfiguration getCorsConfiguration(HttpServletRequest request) {Assert.notNull(this.handlerMappings, "Handler mappings not initialized");HttpServletRequest wrapper = new RequestAttributeChangeIgnoringWrapper(request);for (HandlerMapping handlerMapping : this.handlerMappings) {HandlerExecutionChain handler = null;try {handler = handlerMapping.getHandler(wrapper);}catch (Exception ex) {// Ignore}if (handler == null) {continue;}if (handler.getInterceptors() != null) {for (HandlerInterceptor interceptor : handler.getInterceptors()) {if (interceptor instanceof CorsConfigurationSource) {return ((CorsConfigurationSource) interceptor).getCorsConfiguration(wrapper);}}}if (handler.getHandler() instanceof CorsConfigurationSource) {return ((CorsConfigurationSource) handler.getHandler()).getCorsConfiguration(wrapper);}}return null;}private static List<HandlerMapping> initHandlerMappings(ApplicationContext applicationContext) {// 获取容器中所有类型为 HandlerMapping 的 beanMap<String, HandlerMapping> beans = BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, HandlerMapping.class, true, false);if (!beans.isEmpty()) {List<HandlerMapping> mappings = new ArrayList<>(beans.values());AnnotationAwareOrderComparator.sort(mappings);return Collections.unmodifiableList(mappings);}// 容器中不存在类型为 HandlerMapping 的 bean,// 此时使用 initFallback 创建 DispatcherServlet.properties 文件中// 缺省定义的类型为 HandlerMapping 的 beanreturn Collections.unmodifiableList(initFallback(applicationContext));}private static List<HandlerMapping> initFallback(ApplicationContext applicationContext) {Properties props;String path = "DispatcherServlet.properties";try {Resource resource = new ClassPathResource(path, DispatcherServlet.class);props = PropertiesLoaderUtils.loadProperties(resource);}catch (IOException ex) {throw new IllegalStateException("Could not load '" + path + "': " + ex.getMessage());}String value = props.getProperty(HandlerMapping.class.getName());String[] names = StringUtils.commaDelimitedListToStringArray(value);List<HandlerMapping> result = new ArrayList<>(names.length);for (String name : names) {try {Class<?> clazz = ClassUtils.forName(name, DispatcherServlet.class.getClassLoader());// 使用容器创建 bean，该动作会使所创建的 bean 经历相应的生命周期处理，比如初始化，属性设置等等  Object mapping = applicationContext.getAutowireCapableBeanFactory().createBean(clazz);result.add((HandlerMapping) mapping);}catch (ClassNotFoundException ex) {throw new IllegalStateException("Could not find default HandlerMapping [" + name + "]");}}return result;}/*** Request wrapper that ignores request attribute changes.* 定义一个给当前 HandlerMappingIntrospector 使用的 HttpServletRequestWrapper，* 其方法 setAttribute 实现为空，主要是用于避免属性修改，也就是保持对所访问的 request 不做修改*/private static class RequestAttributeChangeIgnoringWrapper extends HttpServletRequestWrapper {public RequestAttributeChangeIgnoringWrapper(HttpServletRequest request) {super(request);}@Overridepublic void setAttribute(String name, Object value) {// Ignore attribute change...}}}

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Spring MVC : HandlerMappingIntrospector

概述

使用

源代码

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