AbstractDetectingUrlHandlerMapping是通过扫描方式注册Handler,收到请求时由AbstractUrlHandlerMapping的getHandlerInternal进行分发.

共有5个子类,一个抽象类.

与SimpleUrlHandlerMapping类似,通过覆写initApplicationContext,然后调用detectHandlers进行初始化.

detectHandlers通过BeanFactoryUtils扫描应用下的Object,然后预留determineUrlsForHandler给子类根据Handler生成对应的url.

注册使用的registerHandler依然由AbstractUrlHandlerMapping提供.

// AbstractDetectingUrlHandlerMapping /** * Calls the {@link #detectHandlers()} method in addition to the * superclass's initialization. */ @Override public void initApplicationContext() throws ApplicationContextException { super.initApplicationContext(); detectHandlers(); }

这边一样是调用AbstractHandlerMapping的initApplicationContext初始化拦截器.

主角上场,detectHandlers,扫描Handlers

// AbstractDetectingUrlHandlerMapping /** * Register all handlers found in the current ApplicationContext. * <p>The actual URL determination for a handler is up to the concrete * {@link #determineUrlsForHandler(String)} implementation. A bean for * which no such URLs could be determined is simply not considered a handler. * @throws org.springframework.beans.BeansException if the handler couldn't be registered * @see #determineUrlsForHandler(String) */ protected void detectHandlers() throws BeansException { if (logger.isDebugEnabled()) { logger.debug("Looking for URL mappings in application context: " + getApplicationContext()); } String[] beanNames = (this.detectHandlersInAncestorContexts ? BeanFactoryUtils.beanNamesForTypeIncludingAncestors(getApplicationContext(), Object.class) : getApplicationContext().getBeanNamesForType(Object.class)); // Take any bean name that we can determine URLs for. for (String beanName : beanNames) { String[] urls = determineUrlsForHandler(beanName); if (!ObjectUtils.isEmpty(urls)) { // URL paths found: Let's consider it a handler. registerHandler(urls, beanName); } else { if (logger.isDebugEnabled()) { logger.debug("Rejected bean name '" + beanName + "': no URL paths identified"); } } } }

这边预留的模板方法定义如下:

/** * Determine the URLs for the given handler bean. * @param beanName the name of the candidate bean * @return the URLs determined for the bean, * or {@code null} or an empty array if none */ protected abstract String[] determineUrlsForHandler(String beanName); 我们再来看看模板方法在BeanNameUrlHandlerMapping和AbstractControllerUrlHandlerMapping中的实现吧. BeanNameUrlHandlerMapping非常简单,就实现了determineUrlsForHandler. 其中的alias应该是应该就是通过beanName在配置文件中配置的. // BeanNameUrlHandlerMapping /** * Checks name and aliases of the given bean for URLs, starting with "/". */ @Override protected String[] determineUrlsForHandler(String beanName) { List<String> urls = new ArrayList<String>(); if (beanName.startsWith("/")) { urls.add(beanName); } String[] aliases = getApplicationContext().getAliases(beanName); for (String alias : aliases) { if (alias.startsWith("/")) { urls.add(alias); } } return StringUtils.toStringArray(urls); }

再来看看AbstractControllerUrlHandlerMapping中的实现

isEligibleForMapping判断controller是否被排除在外(通过包package排除或类class排除).

buildUrlsForHandler由子类实现具体的url生成规则

isControllerType判断是否Controller的子类

buildUrlsForHandler预留给子类生产url的模板方法.

// AbstractControllerUrlHandlerMapping /** * This implementation delegates to {@link #buildUrlsForHandler}, * provided that {@link #isEligibleForMapping} returns {@code true}. */ @Override protected String[] determineUrlsForHandler(String beanName) { Class beanClass = getApplicationContext().getType(beanName); if (isEligibleForMapping(beanName, beanClass)) { return buildUrlsForHandler(beanName, beanClass); } else { return null; } } // AbstractControllerUrlHandlerMapping /**判断controller是否被排除在外(通过包package排除或类class排除). * Determine whether the specified controller is excluded from this mapping. * @param beanName the name of the controller bean * @param beanClass the concrete class of the controller bean * @return whether the specified class is excluded * @see #setExcludedPackages * @see #setExcludedClasses */ protected boolean isEligibleForMapping(String beanName, Class beanClass) { if (beanClass == null) { if (logger.isDebugEnabled()) { logger.debug("Excluding controller bean '" + beanName + "' from class name mapping " + "because its bean type could not be determined"); } return false; } if (this.excludedClasses.contains(beanClass)) { if (logger.isDebugEnabled()) { logger.debug("Excluding controller bean '" + beanName + "' from class name mapping " + "because its bean class is explicitly excluded: " + beanClass.getName()); } return false; } String beanClassName = beanClass.getName(); for (String packageName : this.excludedPackages) { if (beanClassName.startsWith(packageName)) { if (logger.isDebugEnabled()) { logger.debug("Excluding controller bean '" + beanName + "' from class name mapping " + "because its bean class is defined in an excluded package: " + beanClass.getName()); } return false; } } return isControllerType(beanClass); } // AbstractControllerUrlHandlerMapping /** * Determine whether the given bean class indicates a controller type * that is supported by this mapping strategy. * @param beanClass the class to introspect */ protected boolean isControllerType(Class beanClass) { return this.predicate.isControllerType(beanClass); } // ControllerTypePredicate 这边提供2个api,分别判断是Controller的子类还是MultiActionController的子类. /** * Internal helper class that identifies controller types. * * @author Juergen Hoeller * @since .. */ class ControllerTypePredicate { public boolean isControllerType(Class beanClass) { return Controller.class.isAssignableFrom(beanClass); } public boolean isMultiActionControllerType(Class beanClass) { return MultiActionController.class.isAssignableFrom(beanClass); } }

预留生成url的模板方法

// AbstractControllerUrlHandlerMapping /** * Abstract template method to be implemented by subclasses. * @param beanName the name of the bean * @param beanClass the type of the bean * @return the URLs determined for the bean */ protected abstract String[] buildUrlsForHandler(String beanName, Class beanClass);

再来看看AbstractControllerUrlHandlerMapping的2个实现ControllerBeanNameUrlHandlerMapping和ControllerClassNameUrlHandlerMapping.

其实这两个,很简单,一个是根据beanName来生产url,一个是根据className来生产url.

// ControllerBeanNameUrlHandlerMapping @Override protected String[] buildUrlsForHandler(String beanName, Class beanClass) { List<String> urls = new ArrayList<String>(); urls.add(generatePathMapping(beanName)); String[] aliases = getApplicationContext().getAliases(beanName);// 也获取配置的别名 for (String alias : aliases) { urls.add(generatePathMapping(alias)); } return StringUtils.toStringArray(urls); } // ControllerBeanNameUrlHandlerMapping /**对path添加前后缀,还有/ * Prepends a '/' if required and appends the URL suffix to the name. */ protected String generatePathMapping(String beanName) { String name = (beanName.startsWith("/") " + beanName); StringBuilder path = new StringBuilder(); if (!name.startsWith(this.urlPrefix)) { path.append(this.urlPrefix); } path.append(name); if (!name.endsWith(this.urlSuffix)) { path.append(this.urlSuffix); } return path.toString(); } // ControllerClassNameUrlHandlerMapping

直接委托给generatePathMappings实现

@Override protected String[] buildUrlsForHandler(String beanName, Class beanClass) { return generatePathMappings(beanClass); } // ControllerClassNameUrlHandlerMapping

通过buildPathPrefix获取path的前缀

通过ClassUtils获取className,如BookController(不带包名),同时使用cglib代理的问题一并解决

根据大小写是否敏感,转换className(默认caseSensitive = false;)

isMultiActionControllerType判断Controller是否MultiActionController的子类,就是controller是否包含多个handler

/** * Generate the actual URL paths for the given controller class. * <p>Subclasses may choose to customize the paths that are generated * by overriding this method. * @param beanClass the controller bean class to generate a mapping for * @return the URL path mappings for the given controller */ protected String[] generatePathMappings(Class beanClass) { StringBuilder pathMapping = buildPathPrefix(beanClass); String className = ClassUtils.getShortName(beanClass); String path = (className.endsWith(CONTROLLER_SUFFIX) ? className.substring(, className.lastIndexOf(CONTROLLER_SUFFIX)) : className); if (path.length() > ) { if (this.caseSensitive) { pathMapping.append(path.substring(, ).toLowerCase()).append(path.substring()); } else { pathMapping.append(path.toLowerCase()); } } if (isMultiActionControllerType(beanClass)) { return new String[] {pathMapping.toString(), pathMapping.toString() + "/*"}; } else { return new String[] {pathMapping.toString() + "*"}; } } // ControllerClassNameUrlHandlerMapping /** * Build a path prefix for the given controller bean class. * @param beanClass the controller bean class to generate a mapping for * @return the path prefix, potentially including subpackage names as path elements */ private StringBuilder buildPathPrefix(Class beanClass) { StringBuilder pathMapping = new StringBuilder(); if (this.pathPrefix != null) { pathMapping.append(this.pathPrefix); pathMapping.append("/"); } else { pathMapping.append("/"); } if (this.basePackage != null) { String packageName = ClassUtils.getPackageName(beanClass); if (packageName.startsWith(this.basePackage)) { String subPackage = packageName.substring(this.basePackage.length()).replace('.', '/'); pathMapping.append(this.caseSensitive ? subPackage : subPackage.toLowerCase()); pathMapping.append("/"); } } return pathMapping; } // AbstractControllerUrlHandlerMapping

predicate.isMultiActionControllerType具体实现看上面的ControllerTypePredicate

/** * Determine whether the given bean class indicates a controller type * that dispatches to multiple action methods. * @param beanClass the class to introspect */ protected boolean isMultiActionControllerType(Class beanClass) { return this.predicate.isMultiActionControllerType(beanClass); }

以上所述是小编给大家介绍的SpringMVC源码解读之 HandlerMapping - AbstractDetectingUrlHandlerMapping系列初始化的相关知识，希望对大家有所帮助！