整體思路
Spring Mvc通過HandlerMapping返回執行鏈。在Spring容器中有多中不同的HandlerMapping實現,其對應不同的映射配置方式。在使用@RequestMapping註解時,SpringMvc通過RequestMappingHandlerMapping類的Bean解析、註冊、緩存映射關係,並提供匹配執行鏈的功能。
RequestMappingHandlerMapping
1 解析 url-method 映射關係 思路
RequestMappingHandlerMapping實現了InitializingBean接口,在其初始化時執行afterPropertiesSet方法。在此方法中其遍歷ApplicationContext中所有Bean,通過反射判斷其類型Class上是否有@Controller或@RequestMapping註解。
若Class上有此類註解說明這個Bean是Controller。則執行detectHandlerMethods(beanName)方法,反射(clazz.getMethods())並遍歷此Bean的Method[],通過反射method.getAnnotation(RequestMapping)判斷並獲取方法上標註的@RequestMapping配置信息。將@RequestMapping信息封裝成RequestMappingInfo,將此method封裝成HandlerMethod。註冊到RequestMappingHandlerMapping的mappingRegistry中。
2 註冊並緩存 url-method 映射關係
RequestMappingHandlerMapping中的mappingRegistry對象中成員變量:各種Map還有一個讀寫鎖。
mappingRegistry的各個主要變量
3 接收請求在RequestMappingHandlerMapping中查找返回映射
通過request的請求URL從urlLookup中找到對應RequestMappingInfo,再通過RequestMappingInfo在mappingLookup中找到HandlerMethod。HandlerMethod爲url對應的@RequestMapping標註執行方法。
解析註冊具體實現
WebConfig上使用了@EnableWebMvc註解,這個註解導入了DelegatingWebMvcConfiguration配置,在DelegatingWebMvcConfiguration的父類WebMvcConfigurationSupport創建了RequestMappingHandlerMapping。
@Bean
public RequestMappingHandlerMapping requestMappingHandlerMapping() {
RequestMappingHandlerMapping mapping = createRequestMappingHandlerMapping();
//...省略屬性設置
return mapping;
}
RequestMappingHandlerMapping加載@RequestMapping
我一開始也不知道創建RequestMappingHandlerMapping作用,後來看到它的類圖就明白加載過程。
RequestMappingHandlerMapping的父類實現了InitializingBean,那麼在初始化的時候就會調用afterPropertiesSet方法。看下父類afterPropertiesSet的實現:
@Override
public void afterPropertiesSet() {
initHandlerMethods();
}
protected void initHandlerMethods() {
if (logger.isDebugEnabled()) {
logger.debug("Looking for request mappings in application context: " + getApplicationContext());
}
//detectHandlerMethodsInAncestorContexts默認false,所以是得到所有的beanNames
String[] beanNames = (this.detectHandlerMethodsInAncestorContexts ?
BeanFactoryUtils.beanNamesForTypeIncludingAncestors(getApplicationContext(), Object.class) :
getApplicationContext().getBeanNamesForType(Object.class));
for (String beanName : beanNames) {
if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {
Class<?> beanType = null;
try {
beanType = getApplicationContext().getType(beanName);
}
catch (Throwable ex) {
// An unresolvable bean type, probably from a lazy bean - let's ignore it.
if (logger.isDebugEnabled()) {
logger.debug("Could not resolve target class for bean with name '" + beanName + "'", ex);
}
}
//2. isHandler由子類實現
if (beanType != null && isHandler(beanType)) {
//3. 查找controller中有@RequestMapping註解的方法,並註冊到請求
detectHandlerMethods(beanName);
}
}
}
//空方法
handlerMethodsInitialized(getHandlerMethods());
}
afterPropertiesSet實現交給了initHandlerMethods,initHandlerMethods的執行流程如下:
- 得到所有的beanName
- 遍歷beanNames,調用isHandler判斷bean是不是一個controller,isHandler由子類實現,RequestMappingHandlerMapping的實現如下,判斷bean中有沒有Controller或RequestMapping
@Override
protected boolean isHandler(Class<?> beanType) {
return (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) ||
AnnotatedElementUtils.hasAnnotation(beanType, RequestMapping.class));
}
- 查找controller中有@RequestMapping註解的方法,並註冊到請求容器中
protected void detectHandlerMethods(final Object handler) {
//1. 得到controller真實類型
Class<?> handlerType = (handler instanceof String ?
getApplicationContext().getType((String) handler) : handler.getClass());
final Class<?> userType = ClassUtils.getUserClass(handlerType);
//3. 封裝所有的Method和RequestMappingInfo到Map中
Map<Method, T> methods = MethodIntrospector.selectMethods(userType,
new MethodIntrospector.MetadataLookup<T>() {
@Override
public T inspect(Method method) {
try {
//2. 根據方法上的@RequestMapping信息構建RequestMappingInfo
return getMappingForMethod(method, userType);
}
catch (Throwable ex) {
throw new IllegalStateException("Invalid mapping on handler class [" +
userType.getName() + "]: " + method, ex);
}
}
});
if (logger.isDebugEnabled()) {
logger.debug(methods.size() + " request handler methods found on " + userType + ": " + methods);
}
for (Map.Entry<Method, T> entry : methods.entrySet()) {
Method invocableMethod = AopUtils.selectInvocableMethod(entry.getKey(), userType);
T mapping = entry.getValue();
//4. 將RequestMappingInfo註冊到請求容器中
registerHandlerMethod(handler, invocableMethod, mapping);
}
}
detectHandlerMethods是加載請求核心方法,執行流程如下:
(1) 得到controller真實類型,controller可能被代理
(2) 根據方法上的@RequestMapping信息構建RequestMappingInfo,由RequestMappingHandlerMapping實現。從代碼上可以看出,必須方法上聲明@RequestMapping,類上的@RequestMapping纔會生效。
@Override
protected RequestMappingInfo getMappingForMethod(Method method, Class<?> handlerType) {
//1. 根據方法上的@RequestMapping創建RequestMappingInfo
RequestMappingInfo info = createRequestMappingInfo(method);
if (info != null) {
//2. 查找類上是否有@RequestMapping,如果有則和方法上的組合
RequestMappingInfo typeInfo = createRequestMappingInfo(handlerType);
if (typeInfo != null) {
info = typeInfo.combine(info);
}
}
return info;
}
- 封裝所有的Method和RequestMappingInfo到Map中
- 將RequestMappingInfo註冊到請求容器中
protected void registerHandlerMethod(Object handler, Method method, T mapping) {
this.mappingRegistry.register(mapping, handler, method);
}
這裏就不再分析register方法的實現過程,主要是根據handler,method封裝成HandlerMethod,再請求的時候會得到HandlerMethod,然後反射調用。