SpringMVC源码剖析2——处理器映射器

1.处理器映射器 HandlerMapping

一句话概括作用: 为 我 们 建 立 起 @RequestMapping 注 解 和 控 制 器 方 法 的 对 应 关 系 。

怎么去查看

第一步:

处理器映射器的实体类:
RequestMappingHandlerMapping   
父类  
RequestMappingInfoHandlerMapping
父类的父类
AbstractHandlerMethodMapping
父类的父类的父类
AbstractHandlerMapping

第二步:找到对应的方法,获取拦截的方法

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public Map<T, HandlerMethod> getHandlerMethods() {    this.mappingRegistry.acquireReadLock();    try {       return Collections.unmodifiableMap(this.mappingRegistry.getMappings());    }    finally {       this.mappingRegistry.releaseReadLock();    } }   getMappings()代码内容 public Map<T, HandlerMethod> getMappings() {    return this.mappingLookup; }

<ignore_js_op>
此处能看到一个无界HashMap,存储的是映射关系

那么什么时候存进去的呢?
在AbstractHandlerMethodMapping类中有如下代码:
扫描ApplicationContext中的bean，检测并注册处理程序方法。用来扫描bean的

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protected void initHandlerMethods() {    if (logger.isDebugEnabled()) {       logger.debug("Looking for request mappings in application context: " + getApplicationContext());    }    String[] beanNames = (this.detectHandlerMethodsInAncestorContexts ?          BeanFactoryUtils.beanNamesForTypeIncludingAncestors(obtainApplicationContext(), Object.class) :          obtainApplicationContext().getBeanNamesForType(Object.class));        for (String beanName : beanNames) {       if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {          Class<?> beanType = null;          try {             beanType = obtainApplicationContext().getType(beanName);          }          catch (Throwable ex) {             // An unresolvable bean type, probably from a lazy bean - let's ignore it.             if (logger.isDebugEnabled()) {                logger.debug("Could not resolve target class for bean with name '" + beanName + "'", ex);             }          }          if (beanType != null && isHandler(beanType)) {             detectHandlerMethods(beanName);          }       }    }    handlerMethodsInitialized(getHandlerMethods()); }

上述方法将扫描到的Colltroler类当做参数传递到下面的方法,通过反射获取.class字节码,然后再通过反射将方法和方法上面的路径找到存到map中
detectHandlerMethods(beanName);

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protected void detectHandlerMethods(final Object handler) {    Class<?> handlerType = (handler instanceof String ?          obtainApplicationContext().getType((String) handler) : handler.getClass());        if (handlerType != null) {       final Class<?> userType = ClassUtils.getUserClass(handlerType);       Map<Method, T> methods = MethodIntrospector.selectMethods(userType,             (MethodIntrospector.MetadataLookup<T>) method -> {                try {                   return getMappingForMethod(method, userType);                }                catch (Throwable ex) {                   throw new IllegalStateException("Invalid mapping on handler class [" +                         userType.getName() + "]: " + method, ex);                }             });       if (logger.isDebugEnabled()) {          logger.debug(methods.size() + " request handler methods found on " + userType + ": " + methods);       }       for (Map.Entry<Method, T> entry : methods.entrySet()) {          Method invocableMethod = AopUtils.selectInvocableMethod(entry.getKey(), userType);          T mapping = entry.getValue();          registerHandlerMethod(handler, invocableMethod, mapping);       }    } }

registerHandlerMethod(handler, invocableMethod, mapping);
注册处理程序方法及其唯一映射。在启动时调用

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protected void registerHandlerMethod(Object handler, Method method, T mapping) {    this.mappingRegistry.register(mapping, handler, method); }

先加锁,后将方法和映射放入Map中的
register(mapping, handler, method);

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public void register(T mapping, Object handler, Method method) {    this.readWriteLock.writeLock().lock();    try {       HandlerMethod handlerMethod = createHandlerMethod(handler, method);       assertUniqueMethodMapping(handlerMethod, mapping);           if (logger.isInfoEnabled()) {          logger.info("Mapped \"" + mapping + "\" onto " + handlerMethod);       }       this.mappingLookup.put(mapping, handlerMethod);           List<String> directUrls = getDirectUrls(mapping);       for (String url : directUrls) {          this.urlLookup.add(url, mapping);       }           String name = null;       if (getNamingStrategy() != null) {          name = getNamingStrategy().getName(handlerMethod, mapping);          addMappingName(name, handlerMethod);       }