SpringMVC 这么重要，怎么能错过，搞起~
在初始化容器的时候，会把url与类方法的映射关系注册进去，一切从AbstractHandlerMethodMapping 类说起，找到该类下的initHandlerMethods() 方法，代码如下：
protected void initHandlerMethods() {
// 获取容器初始化的bean,遍历
for (String beanName : getCandidateBeanNames()) {
if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {
processCandidateBean(beanName);
}
}
handlerMethodsInitialized(getHandlerMethods());
}点击进入processCandidateBean()方法，核心代码如下：
protected void processCandidateBean(String beanName) {
Class beanType = null;
// 获取bean的类型
beanType = obtainApplicationContext().getType(beanName);
// 如果有注解 @Controller 或 @RequestMapping，则进入
if (beanType != null && isHandler(beanType)) {
detectHandlerMethods(beanName);
}
}isHandler()方法很简单，就是判断beanType是否有 @Controller 或 @RequestMapping 注解：
protected boolean isHandler(Class beanType) {
return (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) ||
AnnotatedElementUtils.hasAnnotation(beanType,equestMapping.class));
}回到 processCandidateBean()方法，点击 detectHandlerMethods()，进入，核心代码：
protected void detectHandlerMethods(Object handler) {
Class handlerType = (handler instanceof String ?
obtainApplicationContext().getType((String) handler) : handler.getClass());
if (handlerType != null) {
Class userType = ClassUtils.getUserClass(handlerType);
// 泛型T是实际是 RequestMappingInfo 类型
Map methods = MethodIntrospector.selectMethods(userType,
(MethodIntrospector.MetadataLookup) method -> {
// 获取方法的映射
return getMappingForMethod(method, userType);
});
methods.forEach((method, mapping) -> {
Method invocableMethod =
AopUtils.selectInvocableMethod(method,userType);
// 注册方法
registerHandlerMethod(handler, invocableMethod, mapping);
});
}
} 点击 getMappingForMethod()方法，核心代码：
protected RequestMappingInfo getMappingForMethod(Method method, Class handlerType) {
// 创建方法的 RequestMappingInfo
RequestMappingInfo info = createRequestMappingInfo(method);
if (info != null) {
// 创建类的 RequestMappingInfo
RequestMappingInfo typeInfo = createRequestMappingInfo(handlerType);
if (typeInfo != null) {
// 合并方法和类的 @RequestMapping
info = typeInfo.combine(info);
}
String prefix = getPathPrefix(handlerType);
if (prefix != null) {
info = RequestMappingInfo.paths(prefix).options(this.config)
.build().combine(info);
}
}
}点击 createRequestMappingInfo()进去，代码很简单：
private RequestMappingInfo createRequestMappingInfo(AnnotatedElement element) {
// 找到 element 的 @RequestMapping 注解
RequestMapping requestMapping = AnnotatedElementUtils.findMergedAnnotation(element, RequestMapping.class);
RequestCondition condition = (element instanceof Class ?
getCustomTypeCondition((Class) element) :
getCustomMethodCondition((Method) element));
// 构建 RequestMappingInfo 返回
return (requestMapping != null ?
createRequestMappingInfo(requestMapping,condition) : null);
}回到 getMappingForMethod()方法，点击 typeInfo.combine(info) 进去：
public RequestMappingInfo combine(RequestMappingInfo other) {
String name = combineNames(other);
PathPatternsRequestCondition pathPatterns =
(this.pathPatternsCondition != null && other.pathPatternsCondition != null ? this.pathPatternsCondition.combine(other.pathPatternsCondition) : null);
PatternsRequestCondition patterns =
(this.patternsCondition != null && other.patternsCondition != null ?
this.patternsCondition.combine(other.patternsCondition) : null);
RequestMethodsRequestCondition methods =
this.methodsCondition.combine(other.methodsCondition);
ParamsRequestCondition params =
this.paramsCondition.combine(other.paramsCondition);
HeadersRequestCondition headers =
this.headersCondition.combine(other.headersCondition);
……
return new RequestMappingInfo(name, pathPatterns, patterns,
methods, params, headers, consumes, produces, custom, this.options);
}这个方法也很简单，就是把 patterns、methods、params、headers等合并起来，构建RequestMappingInfo 返回。
我们再回到 detectHandlerMethods() 方法，找到registerHandlerMethod()，点击进入，核心代码：
public void register(T mapping, Object handler, Method method) {
// 构建新的 handlerMethod
HandlerMethod handlerMethod = createHandlerMethod(handler, method);
Set directPaths =
AbstractHandlerMethodMapping.this.getDirectPaths(mapping);
for (String path : directPaths) {
// path是 接口路径，如 /a/b，mapping是 RequestMappingInfo
this.pathLookup.add(path, mapping);
}
String name = null;
if (getNamingStrategy() != null) {
name = getNamingStrategy().getName(handlerMethod, mapping);
// 把方法名和handlerMethod的映射添加到 nameLookup中
addMappingName(name, handlerMethod);
}
this.registry.put(mapping, new MappingRegistration<>(
mapping,handlerMethod, directPaths, name, corsConfig != null));
}
这里有两个很重要的结构：
private final MultiValueMap pathLookup =
new LinkedMultiValueMap<>();
private final Map> nameLookup =
new ConcurrentHashMap<>(); 这两个变量存储了url与类方法的关系。
看我的例子，造的两个接口：
pathLookup存储的结构信息：
nameLookup存储的结构信息：
各位细品，千言万语都汇聚在图中~~