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)

复制代码

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

复制代码

  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