SpringMvc中RequestCondition的作用（三）

github原文链接 https://github.com/DespairYoke/java-advance。创作不易，请给个免费的star，已表支持。

初始化

springmvc初始化时，会回调RequestMappingHandlerMapping中的afterPropertiesSet方法。

@Override
public void afterPropertiesSet() {
    initHandlerMethods();
}

追踪到initHandlerMethods中

if (beanType != null && isHandler(beanType)) {
    detectHandlerMethods(beanName);
}

• isHander(beanType)见名知意，是对beanType类型判断，具体实现代码为

protected boolean isHandler(Class<?> beanType) {
    return (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) ||
            AnnotatedElementUtils.hasAnnotation(beanType, RequestMapping.class));
}

最关键的是detectHandlerMethods(beanName)
负责对所有的controller类进行处理

Map<Method, T> methods = MethodIntrospector.selectMethods(userType,
    (MethodIntrospector.MetadataLookup<T>) method -> {
            return getMappingForMethod(method, userType);
    });

• method为方法名，userType为当前处理的类。遍历该类中的所有方法，对方法进行参数路径请求方式等就行处理。
  下面看下getMappingForMethod是如何对不同方法进行处理的。

protected RequestMappingInfo getMappingForMethod(Method method, Class<?> handlerType) {
    RequestMappingInfo info = createRequestMappingInfo(method);
    if (info != null) {
        RequestMappingInfo typeInfo = createRequestMappingInfo(handlerType); //handlerType 是类 这里为了解决类上的@RequestMapping使用
        if (typeInfo != null) {
            info = typeInfo.combine(info);
        }
    }
    return info;
}

可以看出为每个方法都创建了一个RequestMappingInfo，而RequestMappingInfo正是RequestCondition集合，记录了请路径、参数、方式、头等。可以看下对象内容

private final MyPatternsRequestCondition patternsCondition;

private final MyRequestMethodsRequestCondition methodsCondition;

private final MyParamsRequestCondition paramsCondition;

private final MyHeadersRequestCondition headersCondition;

private final MyConsumesRequestCondition consumesCondition;

private final MyProducesRequestCondition producesCondition;

private final MyRequestConditionHolder customConditionHolder;

获取后的RequestMappingInfo会注册到HandlerMethod中

methods.forEach((method, mapping) -> {
    Method invocableMethod = AopUtils.selectInvocableMethod(method, userType);
    registerHandlerMethod(handler, invocableMethod, mapping);
});

最终注册到mappingRegistry中

protected void registerHandlerMethod(Object handler, Method method, T mapping) {
    this.mappingRegistry.register(mapping, handler, method);
    System.out.println("ssss");
}

客户端发起请求

当客户端发起请求后，tomcat的servlet会转发到DispatcherServlet的servce函数回调。经过doDispatch,getHandler,再到AbstractHandlerMapping的getHandler，getHandlerInternal,lookupHandlerMethod
看下lookupHandlerMethod代码

    protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
        List<Match> matches = new ArrayList<>();
        List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
        }

这时，看到了我们初始化时，加载的mappingRegistry，这时就能匹配成功，找到对应的方法。