spring mvc如何计算BEST_MATCHING_PATTERN_ATTRIBUTE

DispatcherServlet

spring-webmvc-4.3.10.RELEASE-sources.jar!/org/springframework/web/servlet/DispatcherServlet.java
代码语言：javascript
复制
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
        HttpServletRequest processedRequest = request;
        HandlerExecutionChain mappedHandler = null;
        boolean multipartRequestParsed = false;
    WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

    try {
        ModelAndView mv = null;
        Exception dispatchException = null;

        try {
            processedRequest = checkMultipart(request);
            multipartRequestParsed = (processedRequest != request);

            // Determine handler for the current request.
            mappedHandler = getHandler(processedRequest);
            if (mappedHandler == null || mappedHandler.getHandler() == null) {
                noHandlerFound(processedRequest, response);
                return;
            }

            // Determine handler adapter for the current request.
            HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

            // Process last-modified header, if supported by the handler.
            String method = request.getMethod();
            boolean isGet = &#34;GET&#34;.equals(method);
            if (isGet || &#34;HEAD&#34;.equals(method)) {
                long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
                if (logger.isDebugEnabled()) {
                    logger.debug(&#34;Last-Modified value for [&#34; + getRequestUri(request) + &#34;] is: &#34; + lastModified);
                }
                if (new ServletWebRequest(request, response).checkNotModified(lastModified) &amp;&amp; isGet) {
                    return;
                }
            }

            if (!mappedHandler.applyPreHandle(processedRequest, response)) {
                return;
            }

            // Actually invoke the handler.
            mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

            if (asyncManager.isConcurrentHandlingStarted()) {
                return;
            }

            applyDefaultViewName(processedRequest, mv);
            mappedHandler.applyPostHandle(processedRequest, response, mv);
        }
        catch (Exception ex) {
            dispatchException = ex;
        }
        catch (Throwable err) {
            // As of 4.3, we&#39;re processing Errors thrown from handler methods as well,
            // making them available for @ExceptionHandler methods and other scenarios.
            dispatchException = new NestedServletException(&#34;Handler dispatch failed&#34;, err);
        }
        processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
    }
    catch (Exception ex) {
        triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
    }
    catch (Throwable err) {
        triggerAfterCompletion(processedRequest, response, mappedHandler,
                new NestedServletException(&#34;Handler processing failed&#34;, err));
    }
    finally {
        if (asyncManager.isConcurrentHandlingStarted()) {
            // Instead of postHandle and afterCompletion
            if (mappedHandler != null) {
                mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
            }
        }
        else {
            // Clean up any resources used by a multipart request.
            if (multipartRequestParsed) {
                cleanupMultipart(processedRequest);
            }
        }
    }
}</code></pre></div></div><blockquote><p>主要看mappedHandler = getHandler(processedRequest);这段</p></blockquote><div class="rno-markdown-code"><div class="rno-markdown-code-toolbar"><div class="rno-markdown-code-toolbar-info"><div class="rno-markdown-code-toolbar-item is-type"><span class="is-m-hidden">代码语言：</span>javascript</div></div><div class="rno-markdown-code-toolbar-opt"><div class="rno-markdown-code-toolbar-copy"><i class="icon-copy"></i><span class="is-m-hidden">复制</span></div></div></div><div class="developer-code-block"><pre class="prism-token token line-numbers language-javascript"><code class="language-javascript" style="margin-left:0">/**
 * Return the HandlerExecutionChain for this request.
 * &lt;p&gt;Tries all handler mappings in order.
 * @param request current HTTP request
 * @return the HandlerExecutionChain, or {@code null} if no handler could be found
 */
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
    for (HandlerMapping hm : this.handlerMappings) {
        if (logger.isTraceEnabled()) {
            logger.trace(
                    &#34;Testing handler map [&#34; + hm + &#34;] in DispatcherServlet with name &#39;&#34; + getServletName() + &#34;&#39;&#34;);
        }
        HandlerExecutionChain handler = hm.getHandler(request);
        if (handler != null) {
            return handler;
        }
    }
    return null;
}</code></pre></div></div><blockquote><p>这里的handlerMappings主要有：

SimpleUrlHandlerMapping
EndpointHandlerMapping
ReuqestMappingHandlerMapping
BeanNameUrlHandlerMapping
WebMvcConfigurationSupport$EmptyHandlerMapping
主要有抽象类AbstractHandlerMapping来执行
AbstractHandlerMapping#getHandler
spring-webmvc-4.3.10.RELEASE-sources.jar!/org/springframework/web/servlet/handler/AbstractHandlerMapping.java
代码语言：javascript
复制
   /**
     * Look up a handler for the given request, falling back to the default
     * handler if no specific one is found.
     * @param request current HTTP request
     * @return the corresponding handler instance, or the default handler
     * @see #getHandlerInternal
     */
    @Override
    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) {
            String handlerName = (String) handler;
            handler = getApplicationContext().getBean(handlerName);
        }
    HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
    if (CorsUtils.isCorsRequest(request)) {
        CorsConfiguration globalConfig = this.corsConfigSource.getCorsConfiguration(request);
        CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
        CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
        executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
    }
    return executionChain;
}</code></pre></div></div><blockquote><p>这里主要看Object handler = getHandlerInternal(request);这段</p></blockquote><h3 id="7vgs1" name="AbstractUrlHandlerMapping#getHandlerInternal"><strong>AbstractUrlHandlerMapping#getHandlerInternal</strong></h3><p>spring-webmvc-4.3.12.RELEASE-sources.jar!/org/springframework/web/servlet/handler/AbstractUrlHandlerMapping.java</p><div class="rno-markdown-code"><div class="rno-markdown-code-toolbar"><div class="rno-markdown-code-toolbar-info"><div class="rno-markdown-code-toolbar-item is-type"><span class="is-m-hidden">代码语言：</span>javascript</div></div><div class="rno-markdown-code-toolbar-opt"><div class="rno-markdown-code-toolbar-copy"><i class="icon-copy"></i><span class="is-m-hidden">复制</span></div></div></div><div class="developer-code-block"><pre class="prism-token token line-numbers language-javascript"><code class="language-javascript" style="margin-left:0">/**
 * Look up a handler for the URL path of the given request.
 * @param request current HTTP request
 * @return the handler instance, or {@code null} if none found
 */
@Override
protected Object getHandlerInternal(HttpServletRequest request) throws Exception {
    String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
    Object handler = lookupHandler(lookupPath, request);
    if (handler == null) {
        // We need to care for the default handler directly, since we need to
        // expose the PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE for it as well.
        Object rawHandler = null;
        if (&#34;/&#34;.equals(lookupPath)) {
            rawHandler = getRootHandler();
        }
        if (rawHandler == null) {
            rawHandler = getDefaultHandler();
        }
        if (rawHandler != null) {
            // Bean name or resolved handler?
            if (rawHandler instanceof String) {
                String handlerName = (String) rawHandler;
                rawHandler = getApplicationContext().getBean(handlerName);
            }
            validateHandler(rawHandler, request);
            handler = buildPathExposingHandler(rawHandler, lookupPath, lookupPath, null);
        }
    }
    if (handler != null &amp;&amp; logger.isDebugEnabled()) {
        logger.debug(&#34;Mapping [&#34; + lookupPath + &#34;] to &#34; + handler);
    }
    else if (handler == null &amp;&amp; logger.isTraceEnabled()) {
        logger.trace(&#34;No handler mapping found for [&#34; + lookupPath + &#34;]&#34;);
    }
    return handler;
}</code></pre></div></div><blockquote><p>这里主要看lookupHandler</p></blockquote><h3 id="cpuqo" name="AbstractUrlHandlerMapping#lookupHandler"><strong>AbstractUrlHandlerMapping#lookupHandler</strong></h3><p>spring-webmvc-4.3.12.RELEASE-sources.jar!/org/springframework/web/servlet/handler/AbstractUrlHandlerMapping.java</p><div class="rno-markdown-code"><div class="rno-markdown-code-toolbar"><div class="rno-markdown-code-toolbar-info"><div class="rno-markdown-code-toolbar-item is-type"><span class="is-m-hidden">代码语言：</span>javascript</div></div><div class="rno-markdown-code-toolbar-opt"><div class="rno-markdown-code-toolbar-copy"><i class="icon-copy"></i><span class="is-m-hidden">复制</span></div></div></div><div class="developer-code-block"><pre class="prism-token token line-numbers language-javascript"><code class="language-javascript" style="margin-left:0">protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {
    // Direct match?
    Object handler = this.handlerMap.get(urlPath);
    if (handler != null) {
        // Bean name or resolved handler?
        if (handler instanceof String) {
            String handlerName = (String) handler;
            handler = getApplicationContext().getBean(handlerName);
        }
        validateHandler(handler, request);
        return buildPathExposingHandler(handler, urlPath, urlPath, null);
    }

    // Pattern match?
    List&lt;String&gt; matchingPatterns = new ArrayList&lt;String&gt;();
    for (String registeredPattern : this.handlerMap.keySet()) {
        if (getPathMatcher().match(registeredPattern, urlPath)) {
            matchingPatterns.add(registeredPattern);
        }
        else if (useTrailingSlashMatch()) {
            if (!registeredPattern.endsWith(&#34;/&#34;) &amp;&amp; getPathMatcher().match(registeredPattern + &#34;/&#34;, urlPath)) {
                matchingPatterns.add(registeredPattern +&#34;/&#34;);
            }
        }
    }

    String bestMatch = null;
    Comparator&lt;String&gt; patternComparator = getPathMatcher().getPatternComparator(urlPath);
    if (!matchingPatterns.isEmpty()) {
        Collections.sort(matchingPatterns, patternComparator);
        if (logger.isDebugEnabled()) {
            logger.debug(&#34;Matching patterns for request [&#34; + urlPath + &#34;] are &#34; + matchingPatterns);
        }
        bestMatch = matchingPatterns.get(0);
    }
    if (bestMatch != null) {
        handler = this.handlerMap.get(bestMatch);
        if (handler == null) {
            if (bestMatch.endsWith(&#34;/&#34;)) {
                handler = this.handlerMap.get(bestMatch.substring(0, bestMatch.length() - 1));
            }
            if (handler == null) {
                throw new IllegalStateException(
                        &#34;Could not find handler for best pattern match [&#34; + bestMatch + &#34;]&#34;);
            }
        }
        // Bean name or resolved handler?
        if (handler instanceof String) {
            String handlerName = (String) handler;
            handler = getApplicationContext().getBean(handlerName);
        }
        validateHandler(handler, request);
        String pathWithinMapping = getPathMatcher().extractPathWithinPattern(bestMatch, urlPath);

        // There might be multiple &#39;best patterns&#39;, let&#39;s make sure we have the correct URI template variables
        // for all of them
        Map&lt;String, String&gt; uriTemplateVariables = new LinkedHashMap&lt;String, String&gt;();
        for (String matchingPattern : matchingPatterns) {
            if (patternComparator.compare(bestMatch, matchingPattern) == 0) {
                Map&lt;String, String&gt; vars = getPathMatcher().extractUriTemplateVariables(matchingPattern, urlPath);
                Map&lt;String, String&gt; decodedVars = getUrlPathHelper().decodePathVariables(request, vars);
                uriTemplateVariables.putAll(decodedVars);
            }
        }
        if (logger.isDebugEnabled()) {
            logger.debug(&#34;URI Template variables for request [&#34; + urlPath + &#34;] are &#34; + uriTemplateVariables);
        }
        return buildPathExposingHandler(handler, bestMatch, pathWithinMapping, uriTemplateVariables);
    }

    // No handler found...
    return null;
}</code></pre></div></div><blockquote><p>这里就是bestMatch计算的核心</p></blockquote><h3 id="afed9" name="%E8%AE%BE%E7%BD%AE"><strong>设置</strong></h3><p>计算完bestMatch之后，就是设置，主要是调用AbstractUrlHandlerMapping#buildPathExposingHandler</p><div class="rno-markdown-code"><div class="rno-markdown-code-toolbar"><div class="rno-markdown-code-toolbar-info"><div class="rno-markdown-code-toolbar-item is-type"><span class="is-m-hidden">代码语言：</span>javascript</div></div><div class="rno-markdown-code-toolbar-opt"><div class="rno-markdown-code-toolbar-copy"><i class="icon-copy"></i><span class="is-m-hidden">复制</span></div></div></div><div class="developer-code-block"><pre class="prism-token token line-numbers language-javascript"><code class="language-javascript" style="margin-left:0">/**
 * Build a handler object for the given raw handler, exposing the actual
 * handler, the {@link #PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE}, as well as
 * the {@link #URI_TEMPLATE_VARIABLES_ATTRIBUTE} before executing the handler.
 * &lt;p&gt;The default implementation builds a {@link HandlerExecutionChain}
 * with a special interceptor that exposes the path attribute and uri template variables
 * @param rawHandler the raw handler to expose
 * @param pathWithinMapping the path to expose before executing the handler
 * @param uriTemplateVariables the URI template variables, can be {@code null} if no variables found
 * @return the final handler object
 */
protected Object buildPathExposingHandler(Object rawHandler, String bestMatchingPattern,
        String pathWithinMapping, Map&lt;String, String&gt; uriTemplateVariables) {

    HandlerExecutionChain chain = new HandlerExecutionChain(rawHandler);
    chain.addInterceptor(new PathExposingHandlerInterceptor(bestMatchingPattern, pathWithinMapping));
    if (!CollectionUtils.isEmpty(uriTemplateVariables)) {
        chain.addInterceptor(new UriTemplateVariablesHandlerInterceptor(uriTemplateVariables));
    }
    return chain;
}</code></pre></div></div><blockquote><p>而这个方法，new了一个PathExposingHandlerInterceptor</p></blockquote><div class="rno-markdown-code"><div class="rno-markdown-code-toolbar"><div class="rno-markdown-code-toolbar-info"><div class="rno-markdown-code-toolbar-item is-type"><span class="is-m-hidden">代码语言：</span>javascript</div></div><div class="rno-markdown-code-toolbar-opt"><div class="rno-markdown-code-toolbar-copy"><i class="icon-copy"></i><span class="is-m-hidden">复制</span></div></div></div><div class="developer-code-block"><pre class="prism-token token line-numbers language-javascript"><code class="language-javascript" style="margin-left:0">/**
 * Special interceptor for exposing the
 * {@link AbstractUrlHandlerMapping#PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE} attribute.
 * @see AbstractUrlHandlerMapping#exposePathWithinMapping
 */
private class PathExposingHandlerInterceptor extends HandlerInterceptorAdapter {

    private final String bestMatchingPattern;

    private final String pathWithinMapping;

    public PathExposingHandlerInterceptor(String bestMatchingPattern, String pathWithinMapping) {
        this.bestMatchingPattern = bestMatchingPattern;
        this.pathWithinMapping = pathWithinMapping;
    }

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
        exposePathWithinMapping(this.bestMatchingPattern, this.pathWithinMapping, request);
        request.setAttribute(INTROSPECT_TYPE_LEVEL_MAPPING, supportsTypeLevelMappings());
        return true;
    }

}

/**
 * Expose the path within the current mapping as request attribute.
 * @param pathWithinMapping the path within the current mapping
 * @param request the request to expose the path to
 * @see #PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE
 */
protected void exposePathWithinMapping(String bestMatchingPattern, String pathWithinMapping, HttpServletRequest request) {
    request.setAttribute(BEST_MATCHING_PATTERN_ATTRIBUTE, bestMatchingPattern);
    request.setAttribute(PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, pathWithinMapping);
}</code></pre></div></div><blockquote><p>可以看到，这里通过exposePathWithinMapping方法设置了BEST_MATCHING_PATTERN_ATTRIBUTE</p></blockquote>