Spring MVC 之 请求url 带后缀的情况

RequestMappingInfoHandlerMapping 在处理http请求的时候， 如果 请求url 有后缀，如果找不到精确匹配的那个@RequestMapping方法。
那么，就把后缀去掉，然后.* 去匹配，这样，一般都可以匹配。 比如有一个@RequestMapping("/rest"), 那么精确匹配的情况下， 只会匹配/rest请求。 但如果我前端发来一个 /rest.abcdef 这样的请求， 又没有配置 @RequestMapping("/rest.abcdef") 这样映射的情况下， 那么@RequestMapping("/rest") 就会生效。

原理呢？处理链是这样的：
at org.springframework.web.servlet.mvc.condition.PatternsRequestCondition.getMatchingPattern(PatternsRequestCondition.java:254)
at org.springframework.web.servlet.mvc.condition.PatternsRequestCondition.getMatchingPatterns(PatternsRequestCondition.java:230)
at org.springframework.web.servlet.mvc.condition.PatternsRequestCondition.getMatchingCondition(PatternsRequestCondition.java:210)
at org.springframework.web.servlet.mvc.method.RequestMappingInfo.getMatchingCondition(RequestMappingInfo.java:214)
at org.springframework.web.servlet.mvc.method.RequestMappingInfoHandlerMapping.getMatchingMapping(RequestMappingInfoHandlerMapping.java:79)
at org.springframework.web.servlet.mvc.method.RequestMappingInfoHandlerMapping.getMatchingMapping(RequestMappingInfoHandlerMapping.java:56)
at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.addMatchingMappings(AbstractHandlerMethodMapping.java:358)
at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.lookupHandlerMethod(AbstractHandlerMethodMapping.java:328)
at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.getHandlerInternal(AbstractHandlerMethodMapping.java:299)
at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.getHandlerInternal(AbstractHandlerMethodMapping.java:57)
at org.springframework.web.servlet.handler.AbstractHandlerMapping.getHandler(AbstractHandlerMapping.java:299)
at org.springframework.web.servlet.DispatcherServlet.getHandler(DispatcherServlet.java:1104)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:916)

关键是PatternsRequestCondition， 具体来说是这个方法：

AbstractHandlerMethodMapping 的getHandlerInternal：
    protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
        String lookupPath = this.getUrlPathHelper().getLookupPathForRequest(request);
        if (this.logger.isDebugEnabled()) {
            this.logger.debug("Looking up handler method for path " + lookupPath);
        }

        HandlerMethod handlerMethod = this.lookupHandlerMethod(lookupPath, request);// 这里是关键，它去寻找，找到了就找到了，找不到就不会再去寻找了
        if (this.logger.isDebugEnabled()) {
            if (handlerMethod != null) {
                this.logger.debug("Returning handler method [" + handlerMethod + "]");
            } else {
                this.logger.debug("Did not find handler method for [" + lookupPath + "]");
            }
        }

        return handlerMethod != null ? handlerMethod.createWithResolvedBean() : null;
    }

    protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
        List<AbstractHandlerMethodMapping<T>.Match> matches = new ArrayList();
        List<T> directPathMatches = (List)this.urlMap.get(lookupPath); // directPathMatches， 直接匹配， 也可以说是 精确匹配
        if (directPathMatches != null) {
            this.addMatchingMappings(directPathMatches, matches, request);// 如果能够精确匹配， 就会进来这里
        }

        if (matches.isEmpty()) {
            this.addMatchingMappings(this.handlerMethods.keySet(), matches, request);// 如果无法精确匹配， 就会进来这里
        }

        if (!matches.isEmpty()) {
            Comparator<AbstractHandlerMethodMapping<T>.Match> comparator = new AbstractHandlerMethodMapping.MatchComparator(this.getMappingComparator(request));
            Collections.sort(matches, comparator);
            if (this.logger.isTraceEnabled()) {
                this.logger.trace("Found " + matches.size() + " matching mapping(s) for [" + lookupPath + "] : " + matches);
            }

            AbstractHandlerMethodMapping<T>.Match bestMatch = (AbstractHandlerMethodMapping.Match)matches.get(0);
            if (matches.size() > 1) {
                AbstractHandlerMethodMapping<T>.Match secondBestMatch = (AbstractHandlerMethodMapping.Match)matches.get(1);
                if (comparator.compare(bestMatch, secondBestMatch) == 0) {
                    Method m1 = bestMatch.handlerMethod.getMethod();
                    Method m2 = secondBestMatch.handlerMethod.getMethod();
                    throw new IllegalStateException("Ambiguous handler methods mapped for HTTP path '" + request.getRequestURL() + "': {" + m1 + ", " + m2 + "}");
                }
            }

            this.handleMatch(bestMatch.mapping, lookupPath, request);
            return bestMatch.handlerMethod;
        } else {
            return this.handleNoMatch(this.handlerMethods.keySet(), lookupPath, request);
        }
    }

    public List<String> getMatchingPatterns(String lookupPath) {
        List<String> matches = new ArrayList();
        Iterator var3 = this.patterns.iterator();

        while(var3.hasNext()) {
            String pattern = (String)var3.next(); // pattern 是 @RequestMapping 提供的映射
            String match = this.getMatchingPattern(pattern, lookupPath); //  lookupPath + .*  后能够匹配pattern， 那么就不为空
            if (match != null) {
                matches.add(match);// 对于有后缀的情况， .* 后
            }
        }

        Collections.sort(matches, this.pathMatcher.getPatternComparator(lookupPath));
        return matches;
    }

    最关键是这里 getMatchingPatterns ：
    private String getMatchingPattern(String pattern, String lookupPath) {
        if (pattern.equals(lookupPath)) {
            return pattern;
        } else {
            if (this.useSuffixPatternMatch) {
                if (!this.fileExtensions.isEmpty() && lookupPath.indexOf(46) != -1) {
                    Iterator var5 = this.fileExtensions.iterator();

                    while(var5.hasNext()) {
                        String extension = (String)var5.next();
                        if (this.pathMatcher.match(pattern + extension, lookupPath)) {
                            return pattern + extension;
                        }
                    }
                } else {
                    boolean hasSuffix = pattern.indexOf(46) != -1;
                    if (!hasSuffix && this.pathMatcher.match(pattern + ".*", lookupPath)) {
                        return pattern + ".*"; // 关键是这里
                    }
                }
            }

            if (this.pathMatcher.match(pattern, lookupPath)) {
                return pattern;
            } else {
                return this.useTrailingSlashMatch && !pattern.endsWith("/") && this.pathMatcher.match(pattern + "/", lookupPath) ? pattern + "/" : null;
            }
        }
    }

而对于AbstractUrlHandlerMapping ，匹配不上就是匹配不上， 不会进行 +.* 后在匹配。

关键方法是这个：

    protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {
        Object handler = this.handlerMap.get(urlPath);
        if (handler != null) {
            if (handler instanceof String) {
                String handlerName = (String)handler;
                handler = this.getApplicationContext().getBean(handlerName);
            }

            this.validateHandler(handler, request);
            return this.buildPathExposingHandler(handler, urlPath, urlPath, (Map)null);
        } else {
            List<String> matchingPatterns = new ArrayList();
            Iterator var5 = this.handlerMap.keySet().iterator();

            while(var5.hasNext()) {
                String registeredPattern = (String)var5.next();
                if (this.getPathMatcher().match(registeredPattern, urlPath)) {
                    matchingPatterns.add(registeredPattern);
                }
            }

            String bestPatternMatch = null;
            Comparator<String> patternComparator = this.getPathMatcher().getPatternComparator(urlPath);
            if (!matchingPatterns.isEmpty()) {
                Collections.sort(matchingPatterns, patternComparator);
                if (this.logger.isDebugEnabled()) {
                    this.logger.debug("Matching patterns for request [" + urlPath + "] are " + matchingPatterns);
                }

                bestPatternMatch = (String)matchingPatterns.get(0);
            }

            if (bestPatternMatch != null) {
                handler = this.handlerMap.get(bestPatternMatch);
                String pathWithinMapping;
                if (handler instanceof String) {
                    pathWithinMapping = (String)handler;
                    handler = this.getApplicationContext().getBean(pathWithinMapping);
                }

                this.validateHandler(handler, request);
                pathWithinMapping = this.getPathMatcher().extractPathWithinPattern(bestPatternMatch, urlPath);
                Map<String, String> uriTemplateVariables = new LinkedHashMap();
                Iterator var9 = matchingPatterns.iterator();

                while(var9.hasNext()) {
                    String matchingPattern = (String)var9.next();
                    if (patternComparator.compare(bestPatternMatch, matchingPattern) == 0) {
                        Map<String, String> vars = this.getPathMatcher().extractUriTemplateVariables(matchingPattern, urlPath);
                        Map<String, String> decodedVars = this.getUrlPathHelper().decodePathVariables(request, vars);
                        uriTemplateVariables.putAll(decodedVars);
                    }
                }

                if (this.logger.isDebugEnabled()) {
                    this.logger.debug("URI Template variables for request [" + urlPath + "] are " + uriTemplateVariables);
                }

                return this.buildPathExposingHandler(handler, bestPatternMatch, pathWithinMapping, uriTemplateVariables);
            } else {
                return null;
            }
        }
    }

当然， 或许我们可以设置自定义的PathMatcher ，从而到达目的。 默认的 是AntPathMatcher 。