SpringMVC原始碼之Handler註冊、獲取以及請求controller中方法
阿新 • • 發佈：2020-11-19
#### 總結
1. 對requestMappingHandlerMapping進行initializeBean時register Handler
2. http開始請求時，initHandlerMappings，DispatcherServlet 中handlerMappings賦值完成
3. 最後在DispatcherServlet#doDispatch（）中，用對應的HandlerAdapter和Handler通過反射去請求controller中方法
#### 對requestMappingHandlerMapping進行initializeBean時register Handler
呼叫鏈：
> AbstractApplicationContext#refresh() --> AbstractApplicationContext#finishBeanFactoryInitialization() --> DefaultListableBeanFactory#preInstantiateSingletons() --> AbstractBeanFactory#getBean() --> AbstractBeanFactory#doGetBean() --> AbstractAutowireCapableBeanFactory#createBean() --> AbstractAutowireCapableBeanFactory#doCreateBean() --> AbstractAutowireCapableBeanFactory#initializeBean() --> AbstractAutowireCapableBeanFactory#invokeInitMethods() --> RequestMappingHandlerMapping#afterPropertiesSet() --> AbstractHandlerMethodMapping#afterPropertiesSet() --> AbstractHandlerMethodMapping#initHandlerMethods() --> AbstractHandlerMethodMapping#processCandidateBean --> AbstractHandlerMethodMapping#detectHandlerMethods() --> RequestMappingHandlerMapping#registerHandlerMethod() --> AbstractHandlerMethodMapping#registerHandlerMethod()
在AbstractHandlerMethodMapping#initHandlerMethods（）中先獲取所有的beanName，再挑選出符合條件的進行處理
```
protected void initHandlerMethods() {
//獲取容器中所有beanName
for (String beanName : getCandidateBeanNames()) {
if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {
processCandidateBean(beanName);
}
}
handlerMethodsInitialized(getHandlerMethods());
}
```
判斷是Handler的才繼續呼叫detectHandlerMethods方法
```
protected void processCandidateBean(String beanName) {
Class beanType = null;
......
if (beanType != null && isHandler(beanType)) {
detectHandlerMethods(beanName);
}
}
```
滿足handler的條件是（RequestMappingHandlerMapping#isHandler（））：@Controller或@RequestMapping進行註解
```
@Override
protected boolean isHandler(Class beanType) {
return (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) ||
AnnotatedElementUtils.hasAnnotation(beanType, RequestMapping.class));
}
```
滿足條件的，進行註冊
RequestMappingHandlerMapping#registerHandlerMethod()
```
@Override
protected void registerHandlerMethod(Object handler, Method method, RequestMappingInfo mapping) {
super.registerHandlerMethod(handler, method, mapping);
updateConsumesCondition(mapping, method);
}
```
AbstractHandlerMethodMapping#registerHandlerMethod()
```
protected void registerHandlerMethod(Object handler, Method method, T mapping) {
this.mappingRegistry.register(mapping, handler, method);
}
```
完成註冊。AbstractHandlerMethodMapping#register（）
```
public void register(T mapping, Object handler, Method method) {
this.readWriteLock.writeLock().lock();
try {
HandlerMethod handlerMethod = createHandlerMethod(handler, method);
validateMethodMapping(handlerMethod, mapping)