SpringMVC Interceptor 解析，加載源碼流程

本文說什麼

interceptor從哪裏來,怎麼創建，怎麼加載，在哪裏被使用，以xml的配置形式爲例

xml配置解析階段

直接打開spring-webmvc的源碼包找到spring.handlers,這個是spring對於組件xml解析模塊。

打開後一看說明，mvc這個標籤是，是通過這個 org.springframework.web.servlet.config.MvcNamespaceHandler，解析的直接找到看一下

http\://www.springframework.org/schema/mvc=org.springframework.web.servlet.config.MvcNamespaceHandler

發現是

public class MvcNamespaceHandler extends NamespaceHandlerSupport {

	@Override
	public void init() {
		registerBeanDefinitionParser("annotation-driven", new AnnotationDrivenBeanDefinitionParser());
		registerBeanDefinitionParser("default-servlet-handler", new DefaultServletHandlerBeanDefinitionParser());
		registerBeanDefinitionParser("interceptors", new InterceptorsBeanDefinitionParser());
		registerBeanDefinitionParser("resources", new ResourcesBeanDefinitionParser());
		registerBeanDefinitionParser("view-controller", new ViewControllerBeanDefinitionParser());
		registerBeanDefinitionParser("redirect-view-controller", new ViewControllerBeanDefinitionParser());
		registerBeanDefinitionParser("status-controller", new ViewControllerBeanDefinitionParser());
		registerBeanDefinitionParser("view-resolvers", new ViewResolversBeanDefinitionParser());
		registerBeanDefinitionParser("tiles-configurer", new TilesConfigurerBeanDefinitionParser());
		registerBeanDefinitionParser("freemarker-configurer", new FreeMarkerConfigurerBeanDefinitionParser());
		registerBeanDefinitionParser("velocity-configurer", new VelocityConfigurerBeanDefinitionParser());
		registerBeanDefinitionParser("groovy-configurer", new GroovyMarkupConfigurerBeanDefinitionParser());
	}

}

這個就直接找到<mvc:*> 的所有表現對應的解析類了，直接找到

registerBeanDefinitionParser("interceptors", new InterceptorsBeanDefinitionParser());

打開看一下，

	@Override
	public BeanDefinition parse(Element element, ParserContext parserContext) {
		CompositeComponentDefinition compDefinition = new CompositeComponentDefinition(element.getTagName(), parserContext.extractSource(element));
		parserContext.pushContainingComponent(compDefinition);

		RuntimeBeanReference pathMatcherRef = null;
		if (element.hasAttribute("path-matcher")) {
			pathMatcherRef = new RuntimeBeanReference(element.getAttribute("path-matcher"));
		}

		List<Element> interceptors = DomUtils.getChildElementsByTagName(element, "bean", "ref", "interceptor");
		for (Element interceptor : interceptors) {
			RootBeanDefinition mappedInterceptorDef = new RootBeanDefinition(MappedInterceptor.class);
			mappedInterceptorDef.setSource(parserContext.extractSource(interceptor));
			mappedInterceptorDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);

			ManagedList<String> includePatterns = null;
			ManagedList<String> excludePatterns = null;
			Object interceptorBean;
			if ("interceptor".equals(interceptor.getLocalName())) {
				includePatterns = getIncludePatterns(interceptor, "mapping");
				excludePatterns = getIncludePatterns(interceptor, "exclude-mapping");
				Element beanElem = DomUtils.getChildElementsByTagName(interceptor, "bean", "ref").get(0);
				interceptorBean = parserContext.getDelegate().parsePropertySubElement(beanElem, null);
			}
			else {
				interceptorBean = parserContext.getDelegate().parsePropertySubElement(interceptor, null);
			}
			mappedInterceptorDef.getConstructorArgumentValues().addIndexedArgumentValue(0, includePatterns);
			mappedInterceptorDef.getConstructorArgumentValues().addIndexedArgumentValue(1, excludePatterns);
			mappedInterceptorDef.getConstructorArgumentValues().addIndexedArgumentValue(2, interceptorBean);

			if (pathMatcherRef != null) {
				mappedInterceptorDef.getPropertyValues().add("pathMatcher", pathMatcherRef);
			}

			String beanName = parserContext.getReaderContext().registerWithGeneratedName(mappedInterceptorDef);
			parserContext.registerComponent(new BeanComponentDefinition(mappedInterceptorDef, beanName));
		}

		parserContext.popAndRegisterContainingComponent();
		return null;
	}

就找到了對於這些標籤的解析，然後把 interceptors 節點全部生成對應的RootBeanDefinition放入到spring容器中，對於xml的解析都結束了容器中已經都全部的interceptor了

加載interceptor

直接找 AbstractHandlerMapping 這個類，handlerMapping的基礎實現類，裏面把interceptor 初始化，分類。因爲他繼承實現了webapplicationObjectSupport。有幾個初始化方法，這就是初始化把interceptor的入口

org.springframework.web.servlet.handler.AbstractHandlerMapping

sping注入applicationContext,就是調用 初始化的時候調用 initApplicationContext 中開始填充handlerMapping中的intercetor 集合
入口代碼展示

pjavaublic abstract class ApplicationObjectSupport implements ApplicationContextAware {
		.........
@Override
	public final void setApplicationContext(ApplicationContext context) throws BeansException {
		if (context == null && !isContextRequired()) {
			// Reset internal context state.
			this.applicationContext = null;
			this.messageSourceAccessor = null;
		}
		else if (this.applicationContext == null) {
			// Initialize with passed-in context.
			if (!requiredContextClass().isInstance(context)) {
				throw new ApplicationContextException(
						"Invalid application context: needs to be of type [" + requiredContextClass().getName() + "]");
			}
			this.applicationContext = context;
			this.messageSourceAccessor = new MessageSourceAccessor(context);
			initApplicationContext(context); // 入口 入口 入口 入口 入口 入口 
		}
		else {
			// Ignore reinitialization if same context passed in.
			if (this.applicationContext != context) {
				throw new ApplicationContextException(
						"Cannot reinitialize with different application context: current one is [" +
						this.applicationContext + "], passed-in one is [" + context + "]");
			}
		}
	}
	
	protected void initApplicationContext(ApplicationContext context) throws BeansException {
		initApplicationContext();
	}

	protected void initApplicationContext() throws BeansException {
		//子類實現
	}
		.........
	}

public abstract class AbstractHandlerMapping extends WebApplicationObjectSupport
		implements HandlerMapping, Ordered {
	.......
	@Override
	protected void initApplicationContext() throws BeansException {
		extendInterceptors(this.interceptors);
		detectMappedInterceptors(this.mappedInterceptors);//從spring中找到interceptor
		initInterceptors();
	}
	
	/**
	 * 在容器中找到所有的interceptor，一個個放入 AbstractHandlerMapping，然後在對其初始化分類，後面就可以用了
	 **/
	
	protected void detectMappedInterceptors(List<MappedInterceptor> mappedInterceptors) {
		mappedInterceptors.addAll(
				BeanFactoryUtils.beansOfTypeIncludingAncestors(
						getApplicationContext(), MappedInterceptor.class, true, false).values());
	}

	/**
	 * 分類
	 **/
	protected void initInterceptors() {
		if (!this.interceptors.isEmpty()) {
			for (int i = 0; i < this.interceptors.size(); i++) {
				Object interceptor = this.interceptors.get(i);
				if (interceptor == null) {
					throw new IllegalArgumentException("Entry number " + i + " in interceptors array is null");
				}
				if (interceptor instanceof MappedInterceptor) {
					this.mappedInterceptors.add((MappedInterceptor) interceptor);
				}
				else {
					this.adaptedInterceptors.add(adaptInterceptor(interceptor));
				}
			}
		}
	}
	......

}

這樣整個流程就搞一段落

總結

mvc自己的包，自己定義標籤，解析xml把所有的interceptor放入spring中，在初始化handlerMapping 中在一個個找出來，放到 handlermapping 中，在初始化分類準備後面使用

ps:
MappedInterceptor 包換 MappedInterceptor

public final class MappedInterceptor {

	// 需要攔截的url
	private final String[] includePatterns;
	// 排除的url
	private final String[] excludePatterns;

	private final HandlerInterceptor interceptor;
	// 判斷是否符合
	private PathMatcher pathMatcher;