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SpringMVC 这么重要,怎么能错过,搞起~
在初始化容器的时候,会把 url 与类办法的映射关系注册进去,所有从 AbstractHandlerMethodMapping 类说起,找到该类下的 initHandlerMethods() 办法,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() 办法,外围代码如下:
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() 办法很简略,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() 办法,点击 detectHandlerMethods(),进入,外围代码:
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 是理论是 RequestMappingInfo 类型
Map<Method, T> methods = MethodIntrospector.selectMethods(userType,
(MethodIntrospector.MetadataLookup<T>) method -> {
// 获取办法的映射
return getMappingForMethod(method, userType);
});
methods.forEach((method, mapping) -> {
Method invocableMethod =
AopUtils.selectInvocableMethod(method,userType);
// 注册办法
registerHandlerMethod(handler, invocableMethod, mapping);
});
}
}
点击 getMappingForMethod() 办法,外围代码:
protected RequestMappingInfo getMappingForMethod(Method method, Class<?> handlerType) {
// 创立办法的 RequestMappingInfo
RequestMappingInfo info = createRequestMappingInfo(method);
if (info != null) {
// 创立类的 RequestMappingInfo
RequestMappingInfo typeInfo = createRequestMappingInfo(handlerType);
if (typeInfo != null) {
// 合并办法和类的 @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,代码很简略:
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() 办法,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);
}
这个办法也很简略,就是把 patterns、methods、params、headers 等合并起来,构建 RequestMappingInfo 返回。
咱们再回到 detectHandlerMethods() 办法,找到 registerHandlerMethod(),点击进入,外围代码:
public void register(T mapping, Object handler, Method method) {
// 构建新的 handlerMethod
HandlerMethod handlerMethod = createHandlerMethod(handler, method);
Set<String> directPaths =
AbstractHandlerMethodMapping.this.getDirectPaths(mapping);
for (String path : directPaths) {
// path 是 接口门路,如 /a/b,mapping 是 RequestMappingInfo
this.pathLookup.add(path, mapping);
}
String name = null;
if (getNamingStrategy() != null) {name = getNamingStrategy().getName(handlerMethod, mapping);
// 把办法名和 handlerMethod 的映射增加到 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构造:
private final MultiValueMap<String, T> pathLookup =
new LinkedMultiValueMap<>();
private final Map<String, List<HandlerMethod>> nameLookup =
new ConcurrentHashMap<>();
这两个变量存储了 url 与类办法的关系。
看我的例子,造的两个接口:
pathLookup 存储的构造信息:
nameLookup 存储的构造信息:
各位细品,一言半语都汇聚在图中~~
正文完
发表至: springboot
2021-10-29