1 finishBeanFactoryInitialization->preInstantiateSingletons 
 2 
 3 在preInstantiateSingletons的getBean()的方法中会实例化带有@RequestMapping、@Controller、@RestController的bean,
 4 detectHandlerMethods
 5 
 6     protected void detectHandlerMethods(Object handler) {
 7         Class<?> handlerType = (handler instanceof String ?
 8                 obtainApplicationContext().getType((String) handler) : handler.getClass());
 9 
10         if (handlerType != null) {
11             Class<?> userType = ClassUtils.getUserClass(handlerType);
12             Map<Method, T> methods = MethodIntrospector.selectMethods(userType,
13                     (MethodIntrospector.MetadataLookup<T>) method -> {
14                         try {
15                             return getMappingForMethod(method, userType);
16                         }
17                         catch (Throwable ex) {
18                             throw new IllegalStateException("Invalid mapping on handler class [" +
19                                     userType.getName() + "]: " + method, ex);
20                         }
21                     });
22             if (logger.isTraceEnabled()) {
23                 logger.trace(formatMappings(userType, methods));
24             }
25             //循环遍历controller类中的接口方法，会把接口的URL作为key,接口的具体方法等信息作为value存入一个map中
26             //private final Map<T, MappingRegistration<T>> registry = new HashMap<>();
27 
28             methods.forEach((method, mapping) -> {
29                 Method invocableMethod = AopUtils.selectInvocableMethod(method, userType);
30                 registerHandlerMethod(handler, invocableMethod, mapping);
31             });
32         }
33     }