@RestController
@RequestMapping("/bind")
public class BinderController {
    @GetMapping("str")
    String bindString(String p) {
        return "Bind: " + p;
    }
}

bindString:25, BinderController (com.example.springbootdemo)
invoke0:-1, NativeMethodAccessorImpl (jdk.internal.reflect)
invoke:77, NativeMethodAccessorImpl (jdk.internal.reflect)
invoke:43, DelegatingMethodAccessorImpl (jdk.internal.reflect)
invoke:568, Method (java.lang.reflect)
doInvoke:207, InvocableHandlerMethod (org.springframework.web.method.support)
invokeForRequest:152, InvocableHandlerMethod (org.springframework.web.method.support)
invokeAndHandle:118, ServletInvocableHandlerMethod (org.springframework.web.servlet.mvc.method.annotation)
invokeHandlerMethod:884, RequestMappingHandlerAdapter (org.springframework.web.servlet.mvc.method.annotation)
handleInternal:797, RequestMappingHandlerAdapter (org.springframework.web.servlet.mvc.method.annotation)
handle:87, AbstractHandlerMethodAdapter (org.springframework.web.servlet.mvc.method)
doDispatch:1081, DispatcherServlet (org.springframework.web.servlet)
doService:974, DispatcherServlet (org.springframework.web.servlet)
processRequest:1011, FrameworkServlet (org.springframework.web.servlet)
doGet:903, FrameworkServlet (org.springframework.web.servlet)
service:564, HttpServlet (jakarta.servlet.http)
service:885, FrameworkServlet (org.springframework.web.servlet)
service:658, HttpServlet (jakarta.servlet.http)
// ...

protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
    logRequest(request);
    // ...
    if (this.parseRequestPath) {
		previousRequestPath = (RequestPath) request.getAttribute(ServletRequestPathUtils.PATH_ATTRIBUTE);
		ServletRequestPathUtils.parseAndCache(request);
	}
	try {
		doDispatch(request, response);
	}
    // ...
}

public static RequestPath parseAndCache(HttpServletRequest request) {
    RequestPath requestPath = ServletRequestPath.parse(request);
    request.setAttribute(PATH_ATTRIBUTE, requestPath);
    return requestPath;
}

public void invoke(Request request, Response response) throws IOException, ServletException {
    // ...
    if (!response.isErrorReportRequired()) {
        context.getPipeline().getFirst().invoke(request, response); // 第一次调用
    }
    response.setSuspended(false);
    Throwable t = (Throwable) request.getAttribute(RequestDispatcher.ERROR_EXCEPTION);
    // Look for (and render if found) an application level error page
    if (response.isErrorReportRequired()) {
        // If an error has occurred that prevents further I/O, don't waste time
        // producing an error report that will never be read
        AtomicBoolean result = new AtomicBoolean(false);
        response.getCoyoteResponse().action(ActionCode.IS_IO_ALLOWED, result);
        if (result.get()) {
            if (t != null) {
                throwable(request, response, t);
            } else {
                status(request, response); // 第二次调用
            }
        }
    }
}

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
    processedRequest = checkMultipart(request);
    HandlerExecutionChain mappedHandler = getHandler(processedRequest);
    if (mappedHandler == null) {
        noHandlerFound(processedRequest, response);
        return;
    }
    HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
    ModelAndView mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
    processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}

public interface HandlerMapping {
	HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;
}

public interface HandlerAdapter {
    boolean supports(Object handler);
	ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception;
}

protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
    if (this.handlerMappings != null) {
        for (HandlerMapping mapping : this.handlerMappings) {
            HandlerExecutionChain handler = mapping.getHandler(request);
            if (handler != null) {
                return handler;
            }
        }
    }
    return null;
}

public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
    Object handler = getHandlerInternal(request);
	if (handler == null) {
		handler = getDefaultHandler();
	}
	if (handler == null) {
		return null;
	}
	// Bean name or resolved handler?
	if (handler instanceof String handlerName) {
		handler = obtainApplicationContext().getBean(handlerName);
	}
	HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
	return executionChain;
}

protected Object lookupHandler(
		RequestPath path, String lookupPath, HttpServletRequest request) throws Exception {

	Object handler = getDirectMatch(lookupPath, request);
	if (handler != null) {
		return handler;
	}

	// Pattern match?
	List<PathPattern> matches = null;
	for (PathPattern pattern : this.pathPatternHandlerMap.keySet()) {
		if (pattern.matches(path.pathWithinApplication())) {
			matches = (matches != null ? matches : new ArrayList<>());
			matches.add(pattern);
		}
	}
	if (matches == null) {
		return null;
	}
	if (matches.size() > 1) {
		matches.sort(PathPattern.SPECIFICITY_COMPARATOR);
		if (logger.isTraceEnabled()) {
			logger.trace("Matching patterns " + matches);
		}
	}
	PathPattern pattern = matches.get(0);
	handler = this.pathPatternHandlerMap.get(pattern);
	if (handler instanceof String handlerName) {
		handler = obtainApplicationContext().getBean(handlerName);
	}
	validateHandler(handler, request);
	String pathWithinMapping = pattern.extractPathWithinPattern(path.pathWithinApplication()).value();
	pathWithinMapping = UrlPathHelper.defaultInstance.removeSemicolonContent(pathWithinMapping);
	return buildPathExposingHandler(handler, pattern.getPatternString(), pathWithinMapping, null);
}

public boolean matches(PathContainer pathContainer) {
    if (this.head == null) {
        return !hasLength(pathContainer) ||
            (this.matchOptionalTrailingSeparator && pathContainerIsJustSeparator(pathContainer));
    }
    else if (!hasLength(pathContainer)) {
        if (this.head instanceof WildcardTheRestPathElement || this.head instanceof CaptureTheRestPathElement) {
            pathContainer = EMPTY_PATH; // Will allow CaptureTheRest to bind the variable to empty
        }
        else {
            return false;
        }
    }
    MatchingContext matchingContext = new MatchingContext(pathContainer, false);
    return this.head.matches(0, matchingContext);
}

public boolean matches(int pathIndex, MatchingContext matchingContext) {
    if (pathIndex < matchingContext.pathLength && matchingContext.isSeparator(pathIndex)) {
        if (isNoMorePattern()) {
            if (matchingContext.determineRemainingPath) {
                matchingContext.remainingPathIndex = pathIndex + 1;
                return true;
            }
            else {
                return (pathIndex + 1 == matchingContext.pathLength);
            }
        }
        else {
            pathIndex++;
            return (this.next != null && this.next.matches(pathIndex, matchingContext));
        }
    }
    return false;
}

public boolean matches(int pathIndex, MatchingContext matchingContext) {
    if (pathIndex >= matchingContext.pathLength) {
        // no more path left to match this element
        return false;
    }
    Element element = matchingContext.pathElements.get(pathIndex);
    if (!(element instanceof PathSegment pathSegment)) {
        return false;
    }
    String value = pathSegment.valueToMatch();
    if (value.length() != this.len) {
        // Not enough data to match this path element
        return false;
    }

    if (this.caseSensitive) {
        if (!this.text.equals(value)) {
            return false;
        }
    }
    pathIndex++;
    // ...
    return (this.next != null && this.next.matches(pathIndex, matchingContext));
}

interface PathSegment extends Element {

    /**
     * Return the path segment value, decoded and sanitized, for path matching.
     */
    String valueToMatch();
    char[] valueToMatchAsChars();

    /**
     * Path parameters associated with this path segment.
     * @return an unmodifiable map containing the parameters
     */
    MultiValueMap<String, String> parameters();
}

public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
        throws Exception {

    ((HttpRequestHandler) handler).handleRequest(request, response);
    return null;
}

public void handleRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    // For very general mappings (e.g. "/") we need to check 404 first
    Resource resource = getResource(request);
    if (resource == null) {
        logger.debug("Resource not found");
        response.sendError(HttpServletResponse.SC_NOT_FOUND);
        return;
    }
    // Supported methods and required session
    checkRequest(request);
    // Header phase
	// Apply cache settings, if any
	// Check the media type for the resource
	// Content phase
	if (request.getHeader(HttpHeaders.RANGE) == null) {
        this.resourceHttpMessageConverter.write(resource, mediaType, outputMessage);
    } else {
        ServletServerHttpRequest inputMessage = new ServletServerHttpRequest(request);
        List<HttpRange> httpRanges = inputMessage.getHeaders().getRange();
        response.setStatus(HttpServletResponse.SC_PARTIAL_CONTENT);
        this.resourceRegionHttpMessageConverter.write(
        HttpRange.toResourceRegions(httpRanges, resource), mediaType, outputMessage);
    }
}

protected Resource getResource(HttpServletRequest request) throws IOException {
	String path = (String) request.getAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE);
	if (path == null) {
		throw new IllegalStateException("Required request attribute '" +
				HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE + "' is not set");
	}

	path = processPath(path);
	if (!StringUtils.hasText(path) || isInvalidPath(path)) {
		return null;
	}
	if (isInvalidEncodedPath(path)) {
		return null;
	}

	Assert.state(this.resolverChain != null, "ResourceResolverChain not initialized.");
	Assert.state(this.transformerChain != null, "ResourceTransformerChain not initialized.");

	Resource resource = this.resolverChain.resolveResource(request, path, getLocations());
	if (resource != null) {
		resource = this.transformerChain.transform(request, resource);
	}
	return resource;
}

String pathWithinMapping = pattern.extractPathWithinPattern(path.pathWithinApplication()).value();
pathWithinMapping = UrlPathHelper.defaultInstance.removeSemicolonContent(pathWithinMapping);
return buildPathExposingHandler(handler, pattern.getPatternString(), pathWithinMapping, null);

request.setAttribute(PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, pathWithinMapping);

protected String processPath(String path) {
    path = StringUtils.replace(path, "\\", "/");
    path = cleanDuplicateSlashes(path);
    return cleanLeadingSlash(path);
}
private String cleanLeadingSlash(String path) {
    boolean slash = false;
    for (int i = 0; i < path.length(); i++) {
        if (path.charAt(i) == '/') {
            slash = true;
        }
        else if (path.charAt(i) > ' ' && path.charAt(i) != 127) {
            if (i == 0 || (i == 1 && slash)) {
                return path;
            }
            return (slash ? "/" + path.substring(i) : path.substring(i));
        }
    }
    return (slash ? "/" : "");
}

protected boolean isInvalidPath(String path) {
	if (path.contains("WEB-INF") || path.contains("META-INF")) {
		return true;
	}
	if (path.contains(":/")) {
		String relativePath = (path.charAt(0) == '/' ? path.substring(1) : path);
		if (ResourceUtils.isUrl(relativePath) || relativePath.startsWith("url:")) {
			return true;
        }
    }
	if (path.contains("..") && StringUtils.cleanPath(path).contains("../")) {
		return true;
    }
	return false;
}

public static boolean isUrl(String resourceLocation) {
    if (resourceLocation.startsWith("classpath:")) {
        return true;
    }	
    try {
        new URL(location);
        return true;
    } catch (MalformedURLException ex) {
        return false;
    }
}

public static String cleanPath(String path) {
	String normalizedPath = replace(path, WINDOWS_FOLDER_SEPARATOR, FOLDER_SEPARATOR);
	String pathToUse = normalizedPath;

    // 去除协议部分
	int prefixIndex = pathToUse.indexOf(':');
	String prefix = "";
	if (prefixIndex != -1) {
		prefix = pathToUse.substring(0, prefixIndex + 1);
		if (prefix.contains(FOLDER_SEPARATOR)) {
			prefix = "";
		}
		else {
			pathToUse = pathToUse.substring(prefixIndex + 1);
		}
	}
	if (pathToUse.startsWith(FOLDER_SEPARATOR)) {
		prefix = prefix + FOLDER_SEPARATOR;
		pathToUse = pathToUse.substring(1);
	}

    // 处理路径树
	String[] pathArray = delimitedListToStringArray(pathToUse, FOLDER_SEPARATOR);
	Deque<String> pathElements = new ArrayDeque<>(pathArray.length);
	int tops = 0;
	for (int i = pathArray.length - 1; i >= 0; i--) {
		String element = pathArray[i];
		if (".".equals(element)) {
			// Points to current directory - drop it.
		} else if ("..".equals(element)) {
			// Registering top path found.
			tops++;
		} else {
			if (tops > 0) {
				// Merging path element with element corresponding to top path.
				tops--;
			}
			else {
				// Normal path element found.
				pathElements.addFirst(element);
			}
		}
	}
	// All path elements stayed the same - shortcut
	if (pathArray.length == pathElements.size()) {
		return normalizedPath;
	}
	// Remaining top paths need to be retained.
	for (int i = 0; i < tops; i++) {
		pathElements.addFirst(TOP_PATH);
	}
	// If nothing else left, at least explicitly point to current path.
	if (pathElements.size() == 1 && pathElements.getLast().isEmpty() && !prefix.endsWith(FOLDER_SEPARATOR)) {
		pathElements.addFirst(CURRENT_PATH);
	}

	final String joined = collectionToDelimitedString(pathElements, FOLDER_SEPARATOR);
	// avoid string concatenation with empty prefix
	return prefix.isEmpty() ? joined : prefix + joined;
   }

private boolean isInvalidEncodedPath(String path) {
    if (path.contains("%")) {
        try {
            // Use URLDecoder (vs UriUtils) to preserve potentially decoded UTF-8 chars
            String decodedPath = URLDecoder.decode(path, StandardCharsets.UTF_8);
            if (isInvalidPath(decodedPath)) {
                return true;
            }
            decodedPath = processPath(decodedPath);
            if (isInvalidPath(decodedPath)) {
                return true;
            }
        }
        catch (IllegalArgumentException ex) {
            // May not be possible to decode...
        }
    }
    return false;
}

// org.springframework.web.servlet.resource.PathResourceResolver#getResource()
for (Resource location : locations) {
    String pathToUse = encodeOrDecodeIfNecessary(resourcePath, request, location);
    Resource resource = getResource(pathToUse, location);
    if (resource != null) {
        return resource;
    }
}

protected Resource getResource(String resourcePath, Resource location) throws IOException {
    Resource resource = location.createRelative(resourcePath);
    if (resource.isReadable()) {
        if (checkResource(resource, location)) {
            return resource;
        }
        else if (logger.isWarnEnabled()) {
            Resource[] allowed = getAllowedLocations();
            logger.warn(LogFormatUtils.formatValue(
                "Resource path \"" + resourcePath + "\" was successfully resolved " +
                "but resource \"" + resource.getURL() + "\" is neither under " +
                "the current location \"" + location.getURL() + "\" nor under any of " +
                "the allowed locations " + (allowed != null ? Arrays.asList(allowed) : "[]"), -1, true));
        }
    }
    return null;
}

@Configuration
@EnableWebSecurity
public class SecurityConfig {
    @Bean
    public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
        http.csrf().disable()
                .authorizeHttpRequests((requests) -> requests
                        .requestMatchers("/secret.txt").hasRole("USER")
                        .requestMatchers("/api/flag").hasRole("USER")
                        .requestMatchers("/**").permitAll()
                )
                .formLogin((form) -> form
                        .loginPage("/login").permitAll()
                )
                .logout(LogoutConfigurer::permitAll);
        return http.build();
    }
}

// org.springframework.security.web.FilterChainProxy
private void doFilterInternal(ServletRequest request, ServletResponse response, FilterChain chain)
		throws IOException, ServletException {
	FirewalledRequest firewallRequest = this.firewall.getFirewalledRequest((HttpServletRequest) request);
	HttpServletResponse firewallResponse = this.firewall.getFirewalledResponse((HttpServletResponse) response);
	List<Filter> filters = getFilters(firewallRequest);
	if (filters == null || filters.size() == 0) {
		if (logger.isTraceEnabled()) {
			logger.trace(LogMessage.of(() -> "No security for " + requestLine(firewallRequest)));
		}
		firewallRequest.reset();
		this.filterChainDecorator.decorate(chain).doFilter(firewallRequest, firewallResponse);
		return;
	}
	if (logger.isDebugEnabled()) {
		logger.debug(LogMessage.of(() -> "Securing " + requestLine(firewallRequest)));
	}
	FilterChain reset = (req, res) -> {
		if (logger.isDebugEnabled()) {
			logger.debug(LogMessage.of(() -> "Secured " + requestLine(firewallRequest)));
		}
		// Deactivate path stripping as we exit the security filter chain
		firewallRequest.reset();
		chain.doFilter(req, res);
	};
	this.filterChainDecorator.decorate(reset, filters).doFilter(firewallRequest, firewallResponse);
}

public FirewalledRequest getFirewalledRequest(HttpServletRequest request) throws RequestRejectedException {
    rejectForbiddenHttpMethod(request);
    rejectedBlocklistedUrls(request);
    rejectedUntrustedHosts(request);
    if (!isNormalized(request)) {
        throw new RequestRejectedException("The request was rejected because the URL was not normalized.");
    }
    rejectNonPrintableAsciiCharactersInFieldName(request.getRequestURI(), "requestURI");
    return new StrictFirewalledRequest(request);
}

public StrictHttpFirewall() {
    urlBlocklistsAddAll(FORBIDDEN_SEMICOLON);
    urlBlocklistsAddAll(FORBIDDEN_FORWARDSLASH);
    urlBlocklistsAddAll(FORBIDDEN_DOUBLE_FORWARDSLASH);
    urlBlocklistsAddAll(FORBIDDEN_BACKSLASH);
    urlBlocklistsAddAll(FORBIDDEN_NULL);
    urlBlocklistsAddAll(FORBIDDEN_LF);
    urlBlocklistsAddAll(FORBIDDEN_CR);

    this.encodedUrlBlocklist.add(ENCODED_PERCENT);
    this.encodedUrlBlocklist.addAll(FORBIDDEN_ENCODED_PERIOD);
    this.decodedUrlBlocklist.add(PERCENT);
    this.decodedUrlBlocklist.addAll(FORBIDDEN_LINE_SEPARATOR);
    this.decodedUrlBlocklist.addAll(FORBIDDEN_PARAGRAPH_SEPARATOR);
}

.requestMatchers("/api/flag").hasRole("USER")

List<Filter> filters = getFilters(firewallRequest);

// org.springframework.security.web.access.intercept.AuthorizationFilter#doFilter
AuthorizationDecision decision = this.authorizationManager.check(this::getAuthentication, request);
this.eventPublisher.publishAuthorizationEvent(this::getAuthentication, request, decision);
if (decision != null && !decision.isGranted()) {
    throw new AccessDeniedException("Access Denied");
}
chain.doFilter(request, response);

public AuthorizationDecision check(Supplier<Authentication> authentication, HttpServletRequest request) {
    this.logger.trace(LogMessage.format("Authorizing %s", request));
	for (RequestMatcherEntry<AuthorizationManager<RequestAuthorizationContext>> mapping : this.mappings) {
		RequestMatcher matcher = mapping.getRequestMatcher();
		MatchResult matchResult = matcher.matcher(request);
		if (matchResult.isMatch()) {
			AuthorizationManager<RequestAuthorizationContext> manager = mapping.getEntry();
            this.logger.trace(LogMessage.format("Checking authorization on %s using %s", request, manager));
			return manager.check(authentication,
					new RequestAuthorizationContext(request, matchResult.getVariables()));
		}
	}
    this.logger.trace(LogMessage.of(() -> "Denying request since did not find matching RequestMatcher"));
	return DENY;
}

public MatchResult matcher(HttpServletRequest request) {
	if (notMatchMethodOrServletPath(request)) {
		return MatchResult.notMatch();
	}
	MatchableHandlerMapping mapping = getMapping(request);
	if (mapping == null) {
		return this.defaultMatcher.matcher(request);
	}
	RequestMatchResult result = mapping.match(request, this.pattern);
	return (result != null) ? MatchResult.match(result.extractUriTemplateVariables()) : MatchResult.notMatch();
}

// org.apache.shiro.web.filter.mgt.PathMatchingFilterChainResolver#getChain
final String requestURI = getPathWithinApplication(request);
final String requestURINoTrailingSlash = removeTrailingSlash(requestURI);
for (String pathPattern : filterChainManager.getChainNames()) {
  if (pathMatches(pathPattern, requestURI)) {
    return filterChainManager.proxy(originalChain, pathPattern);
  } else {
    // 针对 Spring Web 的处理
    pathPattern = removeTrailingSlash(pathPattern);
      if (pathMatches(pathPattern, requestURINoTrailingSlash)) {
        return filterChainManager.proxy(originalChain, pathPattern);
      }
  }
}