springMVC是如何做url映射到controller的？

背景

最近要做一个URL到权限的控制，需要根据实际的URL匹配到配置文件，一般的url好处理，但是对于path parameter 的URL就需要做匹配了，所以研读了一下springmvc的源码，看看是如何做的

• 入口 FrameworkServlet
• • .doPost(HttpServletRequest request, HttpServletResponse response)
• DispatcherServlet
• • .doService
• • DispatcherServlet.doDispatch
• • HandlerExecutionChain mappedHandler =getHandler(processedRequest)
    这里有多个handlerMapping,实际用到的是RequestMappingHandlerMapping

this.handlerMappings ={ArrayList@14007} size =7
0={WebMvcEndpointHandlerMapping@13963}
1={ControllerEndpointHandlerMapping@14199}
2={RequestMappingHandlerMapping@9698}
3={BeanNameUrlHandlerMapping@14200}
4= {RouterFunctionMapping@14201}
5={SimpleUrlHandlerMapping@14202}
6={WelcomePageHandlerMapping@14203}

• AbstractHandlerMethodMapping
  从这个mapping 中获取RequestMappingHandlerMapping
• • HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request)

	protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
		List<Match> matches = new ArrayList<>();
		List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
		if (directPathMatches != null) {
			addMatchingMappings(directPathMatches, matches, request);
		}
		if (matches.isEmpty()) {
			// No choice but to go through all mappings...
			addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);
		}

这段代码有意思，先去根据url 去map中找RequestMappingInfo （封装了URL匹配相关信息） ，然后去做URL匹配

• • MappingRegistry 保存了所有的配置

mappingLookup 保存了RequestMappingInfo 和 HandlerMethod 的映射
MultiValueMap<String, T> urlLookup 保存了路径和方法的映射

• 所有的配置信息封装在 RequestMappingInfo

	public RequestMappingInfo getMatchingCondition(HttpServletRequest request) {
		RequestMethodsRequestCondition methods = this.methodsCondition.getMatchingCondition(request);
		if (methods == null) {
			return null;
		}
		ParamsRequestCondition params = this.paramsCondition.getMatchingCondition(request);
		if (params == null) {
			return null;
		}
		HeadersRequestCondition headers = this.headersCondition.getMatchingCondition(request);
		if (headers == null) {
			return null;
		}
		ConsumesRequestCondition consumes = this.consumesCondition.getMatchingCondition(request);
		if (consumes == null) {
			return null;
		}
		ProducesRequestCondition produces = this.producesCondition.getMatchingCondition(request);
		if (produces == null) {
			return null;
		}
		PatternsRequestCondition patterns = this.patternsCondition.getMatchingCondition(request);
		if (patterns == null) {
			return null;
		}
		RequestConditionHolder custom = this.customConditionHolder.getMatchingCondition(request);
		if (custom == null) {
			return null;
		}

		return new RequestMappingInfo(this.name, patterns,
				methods, params, headers, consumes, produces, custom.getCondition());
	}

找到PatternsRequestCondition ，用来做和url做模式匹配

• PatternsRequestCondition

this.pathMatcher = pathMatcher != null ? pathMatcher : new AntPathMatcher();

this.pathMatcher.match("/Task/GetTaskById/{taskid}", "/Task/GetTaskById/123")

这里实际上是spring 的AntPathMatcher 类，直接调用即可匹配带参数的URL

总结

springMVC 做URL匹配，实际上分两步，1，用url去map中找List directPathMatches
2, 遍历List directPathMatches，逐个做pathMatcher