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HandlerMethod: 其实就是对我们写的controller中的method做的一层封装。
// HandlerMethod.class
/**
* Encapsulates information about a handler method consisting of a
* {@linkplain #getMethod() method} and a {@linkplain #getBean() bean}.
* Provides convenient access to method parameters, the method return value,
* method annotations, etc.
*
* <p>The class may be created with a bean instance or with a bean name
* (e.g. lazy-init bean, prototype bean). Use {@link #createWithResolvedBean()}
* to obtain a {@code HandlerMethod} instance with a bean instance resolved
* through the associated {@link BeanFactory}.
*
*/
public class HandlerMethod {}
HandlerMethod是何时被加载：
在AbstractHandlerMethodMapping中会扫描所有的bean，然后找到其中的handler做加载。（判断handler的方法位于RequestMappingHandlerMapping中）
// AbstractHandlerMethodMapping.class
/**
* Detects handler methods at initialization.
*/
@Override
public void afterPropertiesSet() {
initHandlerMethods();
}
/**
* Scan beans in the ApplicationContext, detect and register handler methods.
*/
protected void initHandlerMethods() {
if (logger.isDebugEnabled()) {
logger.debug("Looking for request mappings in application context: " + getApplicationContext());
}
//扫描所有的Bean
String[] beanNames = (this.detectHandlerMethodsInAncestorContexts ?
BeanFactoryUtils.beanNamesForTypeIncludingAncestors(obtainApplicationContext(), Object.class) :
obtainApplicationContext().getBeanNamesForType(Object.class));
for (String beanName : beanNames) {
if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {
Class<?> beanType = null;
try {
beanType = obtainApplicationContext().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);
}
}
//如果是一个handler 则进行加载逻辑
if (beanType != null && isHandler(beanType)) {
detectHandlerMethods(beanName);
}
}
}
handlerMethodsInitialized(getHandlerMethods());
}
/**
* Look for handler methods in a handler.
* @param handler the bean name of a handler or a handler instance
* 这里的handler 其实是一个string 也就是bean的类名
*/
protected void detectHandlerMethods(final Object handler) {
Class<?> handlerType = (handler instanceof String ?
obtainApplicationContext().getType((String) handler) : handler.getClass());
if (handlerType != null) {
final Class<?> userType = ClassUtils.getUserClass(handlerType);
// 获取bean中 method 与 RequestMappingInfo的对应关系，RequestMappingInfo其实就是@requestMapping的信息
Map<Method, T> methods = MethodIntrospector.selectMethods(userType,
(MethodIntrospector.MetadataLookup<T>) method -> {
try {
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);
}
methods.forEach((method, mapping) -> {
Method invocableMethod = AopUtils.selectInvocableMethod(method, userType);
//handler：bean的名称， invocableMethod：可执行的方法，mapping：RequestMappingInfo
registerHandlerMethod(handler, invocableMethod, mapping);
});
}
}
/**
* Register a handler method and its unique mapping. Invoked at startup for
* each detected handler method.
* @param handler the bean name of the handler or the handler instance
* @param method the method to register
* @param mapping the mapping conditions associated with the handler method
* @throws IllegalStateException if another method was already registered
* under the same mapping
*最终去mappingRegistry完成注册逻辑
*/
protected void registerHandlerMethod(Object handler, Method method, T mapping) {
this.mappingRegistry.register(mapping, handler, method);
}
//RequestMappingHandlerMapping.class
/**
* {@inheritDoc}
* <p>Expects a handler to have either a type-level @{@link Controller}
* annotation or a type-level @{@link RequestMapping} annotation.
*/
@Override
protected boolean isHandler(Class<?> beanType) {
return (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) ||
AnnotatedElementUtils.hasAnnotation(beanType, RequestMapping.class));
}
MappingRegistry是AbstractHandlerMethodMapping的一个内部类，内部维护了所有的HandlerMethod的相关映射。
// MappingRegistry.class
// key : Mapping信息
private final Map<T, MappingRegistration<T>> registry = new HashMap<>();
// key : Mapping信息
private final Map<T, HandlerMethod> mappingLookup = new LinkedHashMap<>();
// key : url value:mappping数组
private final MultiValueMap<String, T> urlLookup = new LinkedMultiValueMap<>();
// key：Mapping的名字
private final Map<String, List<HandlerMethod>> nameLookup = new ConcurrentHashMap<>();
private final Map<HandlerMethod, CorsConfiguration> corsLookup = new ConcurrentHashMap<>();
private final ReentrantReadWriteLock readWriteLock = new ReentrantReadWriteLock();
// 存入各种信息
public void register(T mapping, Object handler, Method method) {
this.readWriteLock.writeLock().lock();
try {
HandlerMethod handlerMethod = createHandlerMethod(handler, method);
assertUniqueMethodMapping(handlerMethod, mapping);
if (logger.isInfoEnabled()) {
logger.info("Mapped \"" + mapping + "\" onto " + handlerMethod);
}
this.mappingLookup.put(mapping, handlerMethod);
List<String> directUrls = getDirectUrls(mapping);
for (String url : directUrls) {
this.urlLookup.add(url, mapping);
}
String name = null;
if (getNamingStrategy() != null) {
name = getNamingStrategy().getName(handlerMethod, mapping);
addMappingName(name, handlerMethod);
}
CorsConfiguration corsConfig = initCorsConfiguration(handler, method, mapping);
if (corsConfig != null) {
this.corsLookup.put(handlerMethod, corsConfig);
}
this.registry.put(mapping, new MappingRegistration<>(mapping, handlerMethod, directUrls, name));
}
finally {
this.readWriteLock.writeLock().unlock();
}
}
private void addMappingName(String name, HandlerMethod handlerMethod) {
List<HandlerMethod> oldList = this.nameLookup.get(name);
if (oldList == null) {
oldList = Collections.emptyList();
}
for (HandlerMethod current : oldList) {
if (handlerMethod.equals(current)) {
return;
}
}
if (logger.isTraceEnabled()) {
logger.trace("Mapping name '" + name + "'");
}
List<HandlerMethod> newList = new ArrayList<>(oldList.size() + 1);
newList.addAll(oldList);
newList.add(handlerMethod);
this.nameLookup.put(name, newList);
if (newList.size() > 1) {
if (logger.isTraceEnabled()) {
logger.trace("Mapping name clash for handlerMethods " + newList +
". Consider assigning explicit names.");
}
}
}
HandlerMapping中还有一个重要的作用 加载HandlerInterceptor
HandlerInterceptor是在什么时候被加载的呢
看下来是在WebMvcConfigurationSupport中
// WebMvcConfigurationSupport.class
/**
* Return a {@link RequestMappingHandlerMapping} ordered at 0 for mapping
* requests to annotated controllers.
*/
@Bean
public RequestMappingHandlerMapping requestMappingHandlerMapping() {
RequestMappingHandlerMapping mapping = createRequestMappingHandlerMapping();
mapping.setOrder(0);
mapping.setInterceptors(getInterceptors());
mapping.setContentNegotiationManager(mvcContentNegotiationManager());
mapping.setCorsConfigurations(getCorsConfigurations());
PathMatchConfigurer configurer = getPathMatchConfigurer();
Boolean useSuffixPatternMatch = configurer.isUseSuffixPatternMatch();
Boolean useRegisteredSuffixPatternMatch = configurer.isUseRegisteredSuffixPatternMatch();
Boolean useTrailingSlashMatch = configurer.isUseTrailingSlashMatch();
if (useSuffixPatternMatch != null) {
mapping.setUseSuffixPatternMatch(useSuffixPatternMatch);
}
if (useRegisteredSuffixPatternMatch != null) {
mapping.setUseRegisteredSuffixPatternMatch(useRegisteredSuffixPatternMatch);
}
if (useTrailingSlashMatch != null) {
mapping.setUseTrailingSlashMatch(useTrailingSlashMatch);
}
UrlPathHelper pathHelper = configurer.getUrlPathHelper();
if (pathHelper != null) {
mapping.setUrlPathHelper(pathHelper);
}
PathMatcher pathMatcher = configurer.getPathMatcher();
if (pathMatcher != null) {
mapping.setPathMatcher(pathMatcher);
}
return mapping;
}
其中的getInterceptors方法会去拿到所有的Interceptor
/**
* Provide access to the shared handler interceptors used to configure
* {@link HandlerMapping} instances with. This method cannot be overridden,
* use {@link #addInterceptors(InterceptorRegistry)} instead.
*/
protected final Object[] getInterceptors() {
if (this.interceptors == null) {
InterceptorRegistry registry = new InterceptorRegistry();
addInterceptors(registry);
registry.addInterceptor(new ConversionServiceExposingInterceptor(mvcConversionService()));
registry.addInterceptor(new ResourceUrlProviderExposingInterceptor(mvcResourceUrlProvider()));
this.interceptors = registry.getInterceptors();
}
return this.interceptors.toArray();
}
这里面的addInterceptors方法会讲interceptor注册到registry中，其实就是在WebMvcConfigurerComposite中
private final List<WebMvcConfigurer> delegates = new ArrayList<>();
@Override
public void addInterceptors(InterceptorRegistry registry) {
for (WebMvcConfigurer delegate : this.delegates) {
delegate.addInterceptors(registry);
}
}
可以看到，这里的delegates就是WebMvcConfigurer的集合而我们自己注册interceptor就需要继承这个类，可以参看springMvc中如何使用Interceptor。
