简单流程图

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RequestMappingHandlerMapping的createRequestMappingInfo创建映射

首先获取RequestMapping注解，如果存在就创建一个RequestMappingInfo否则就返回null 。

    @Nullable
    private RequestMappingInfo createRequestMappingInfo(AnnotatedElement element) {
        RequestMapping requestMapping = AnnotatedElementUtils.findMergedAnnotation(element, RequestMapping.class);
        RequestCondition<?> condition = (element instanceof Class ?
                getCustomTypeCondition((Class<?>) element) : getCustomMethodCondition((Method) element));
        return (requestMapping != null ? createRequestMappingInfo(requestMapping, condition) : null);
    }

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其实就是封装方法的RequestMappingInfo注解的属性啦：

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然后是类上的：

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combine合并属性

具体怎么合并的细节就不看了。

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合并后的结果，我们常用的就是uri拼起来了：

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最后放入methodMap返回：

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registerHandlerMethod

注册方法，最终是注册到MappingRegistry中的。

    @Override
    protected void registerHandlerMethod(Object handler, Method method, RequestMappingInfo mapping) {
        super.registerHandlerMethod(handler, method, mapping);
        updateConsumesCondition(mapping, method);
    }
    protected void registerHandlerMethod(Object handler, Method method, T mapping) {
        this.mappingRegistry.register(mapping, handler, method);
    }

MappingRegistry的register

注册各种类型的映射。

        private final Map<T, MappingRegistration<T>> registry = new HashMap<>();

        private final Map<T, HandlerMethod> mappingLookup = new LinkedHashMap<>();

        private final MultiValueMap<String, T> urlLookup = new LinkedMultiValueMap<>();

        private final Map<String, List<HandlerMethod>> nameLookup = new ConcurrentHashMap<>();

        public void register(T mapping, Object handler, Method method) {
            ...
            this.readWriteLock.writeLock().lock();
            try {
                HandlerMethod handlerMethod = createHandlerMethod(handler, method);//创建HandlerMethod
                validateMethodMapping(handlerMethod, mapping);//验证唯一性
                this.mappingLookup.put(mapping, handlerMethod);//方法映射，放入mappingLookup

                List<String> directUrls = getDirectUrls(mapping);
                for (String url : directUrls) {
                    this.urlLookup.add(url, mapping);//url映射，放入mappingLookup，可以多对一
                }

                String name = null;
                if (getNamingStrategy() != null) {
                    name = getNamingStrategy().getName(handlerMethod, mapping);
                    addMappingName(name, handlerMethod);//名字映射，name为类名大写字母+#+方法名，比如UserController的getUser方法就是UC#getUser
                }
                ...
                this.registry.put(mapping, new MappingRegistration<>(mapping, handlerMethod, directUrls, name));//封装成MappingRegistration放入registry
            }
            finally {
                this.readWriteLock.writeLock().unlock();
            }
        }

AbstractHandlerMethodMapping的createHandlerMethod

根据是处理器是String还是对象类型进行不同的HandlerMethod封装，一般初始化的时候还没有实例，只是名字。

    protected HandlerMethod createHandlerMethod(Object handler, Method method) {
        if (handler instanceof String) {//如果是bean名字
            return new HandlerMethod((String) handler,
                    obtainApplicationContext().getAutowireCapableBeanFactory(), method);
        }
        return new HandlerMethod(handler, method);
    }

处理器名字创建：
内部会获取名字对应的类型，进行方法参数信息的封装和ResponseStatus注解相关处理。

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MappingRegistry的validateMethodMapping检查唯一性

如果uri映射HandlerMethod已经存在，且不是同一个HandlerMethod要报异常。

private void validateMethodMapping(HandlerMethod handlerMethod, T mapping) {
            // Assert that the supplied mapping is unique.
            HandlerMethod existingHandlerMethod = this.mappingLookup.get(mapping);
            if (existingHandlerMethod != null && !existingHandlerMethod.equals(handlerMethod)) {
                throw new IllegalStateException(
                        "Ambiguous mapping. Cannot map '" + handlerMethod.getBean() + "' method \n" +
                        handlerMethod + "\nto " + mapping + ": There is already '" +
                        existingHandlerMethod.getBean() + "' bean method\n" + existingHandlerMethod + " mapped.");
            }
        }