RequestMappingHandlerMapping 初始化

RequestMappingHandlerMapping 初始化

graph TD
1(spring環境啓動,加載DocumentationPluginsBootstrapper)-->2(加載接口RequestHandlerProvider的實現類bean)
2-->3(加載RequestMappingInfoHandlerMapping的實現類的bean)
3-->4(這個時候咱們的RequestMappingHandlerMapping就會被加在了)
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代碼內容:

1.加載 DocumentationPluginsBootstrapper
在spring的環境啓動的時候，DocumentationPluginsBootstrapper就會被加載，這個時候，做爲構造函數中的參數List也會被依賴加載

@Component
public class DocumentationPluginsBootstrapper implements SmartLifecycle {
...
@Autowired
    public DocumentationPluginsBootstrapper(DocumentationPluginsManager documentationPluginsManager, List<RequestHandlerProvider> handlerProviders, DocumentationCache scanned, ApiDocumentationScanner resourceListing, TypeResolver typeResolver, Defaults defaults, ServletContext servletContext) {
    }
...
}
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2. 加載WebMvcRequestHandlerProvider
   加載List的時候，會去加載實現了RequestHandlerProvider接口的bean,查看了源代碼，只有WebMvcRequestHandlerProvider一個實現類，好像

@Component
@Order(-2147483648)
public class WebMvcRequestHandlerProvider implements RequestHandlerProvider {
    private final List<RequestMappingInfoHandlerMapping> handlerMappings;
    private final HandlerMethodResolver methodResolver;

    @Autowired
    public WebMvcRequestHandlerProvider(HandlerMethodResolver methodResolver, List<RequestMappingInfoHandlerMapping> handlerMappings) {
        this.handlerMappings = handlerMappings;
        this.methodResolver = methodResolver;
    }
}
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加載WebMvcRequestHandlerProvider的時候，又會去加載List<RequestMappingInfoHandlerMapping>

3. 加載RequestMappingHandlerMapping
   做爲RequestMappingInfoHandlerMapping的子類，RequestMappingHandlerMapping也被加載到了。

在加載RequestMappingHandlerMappingde時候，按照上圖顯示會執行 initHandlerMethods,其中就會完成對HandlerMethod的註冊

/**
 * Look for handler methods in a handler.
 * @param handler the bean name of a handler or a handler instance
 */
protected void detectHandlerMethods(final Object handler) {
	Class<?> handlerType = (handler instanceof String ?
			getApplicationContext().getType((String) handler) : handler.getClass());
	final Class<?> userType = ClassUtils.getUserClass(handlerType);

	Map<Method, T> methods = MethodIntrospector.selectMethods(userType,
			new MethodIntrospector.MetadataLookup<T>() {
				@Override
				public T inspect(Method 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);
	}
	for (Map.Entry<Method, T> entry : methods.entrySet()) {
		Method invocableMethod = AopUtils.selectInvocableMethod(entry.getKey(), userType);
		T mapping = entry.getValue();
		registerHandlerMethod(handler, invocableMethod, mapping);
	}
}
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上面的代碼，遍歷當前bean的全部方法，封裝成RequestMappingInfo，並完成註冊

封裝的RequestMappingInfo的方法getMappingForMethod在RequestMappingHandlerMapping作了實現

4. 註冊HandlerMethod

protected void registerHandlerMethod(Object handler, Method method, T mapping) {
	this.mappingRegistry.register(mapping, handler, method);
}
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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<T>(mapping, handlerMethod, directUrls, name));
	}
	finally {
		this.readWriteLock.writeLock().unlock();
	}
}
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註冊的過程，大體就是對mappingLookup、urlLookup、corsLookup完成註冊 這三個結構內容以下

private final Map<T, HandlerMethod> mappingLookup = new LinkedHashMap<T, HandlerMethod>();

private final MultiValueMap<String, T> urlLookup = new LinkedMultiValueMap<String, T>();

private final Map<HandlerMethod, CorsConfiguration> corsLookup =
		new ConcurrentHashMap<HandlerMethod, CorsConfiguration>();
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這三個結構的內容，會爲後續的請求匹配對應的處理HandlerMethod提供判斷依據

完成上述步驟，能看到下面的日誌打出，標識咱們的請求鏈接已經能夠和處理邏輯的HandlerMethod關聯上了

2019-06-27 22:42:48 752 [restartedMain] [] INFO  o.s.w.s.m.m.a.RequestMappingHandlerMapping - Mapped "{[/api/manager/v1/organization/level/list],methods=[GET]}" onto public java.util.List<java.lang.Integer> com.test.controller.manager.OrganizationController.getOrgLevelList(java.lang.Integer)
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