1. 目录

[TOC]

2. 说明

前面springmvc启动流程已经分析到了拦截器是使用InterceptorsBeanDefinitionParser解析器来解析的

3. 依赖分析

4. 源码分析

4.1. xml说明

在spring中配置了<mvc:interceptors> 标签的会在此解析器中解析得到MappedInterceptor包装类
解析器支持解析三种标签bean,ref,interceptor，从后面源码可以看出来

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<mvc:interceptors>
    <!--在这里创建一个拦截器bean-->
    <bean class="com.kewen.interceptor.GlobalInterceptor"/>
    <!--引用已有的bean-->
    <ref bean="globalInterceptor"/>
    <!--配置条件拦截器-->
    <mvc:interceptor>
        <mvc:mapping path="/**"/>
        <mvc:exclude-mapping path="/login"/>
        <ref bean="helloInterceptor"/>
        <bean class="com.kewen.interceptor.HelloInterceptor"/>
    </mvc:interceptor>
</mvc:interceptors>

4.2. 源码解析

4.2.1. 解析xml加载BeanDifinition

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//InterceptorsBeanDefinitionParser.java
public BeanDefinition parse(Element element, ParserContext context) {
		context.pushContainingComponent(
            new CompositeComponentDefinition(element.getTagName(), context.extractSource(element)));

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

    //拿到对应标签中的元素
    List<Element> interceptors = DomUtils.getChildElementsByTagName(element, "bean", "ref", "interceptor");
    //循环构造MappedInterceptor的Bean定义
    for (Element interceptor : interceptors) {
        RootBeanDefinition mappedInterceptorDef = new RootBeanDefinition(MappedInterceptor.class);
        mappedInterceptorDef.setSource(context.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 = context.getDelegate().parsePropertySubElement(beanElem, null);
        }
        else {
            interceptorBean = context.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);
        }

        //注册到beanDefinitionMap中
        String beanName = context.getReaderContext().registerWithGeneratedName(mappedInterceptorDef);
        context.registerComponent(new BeanComponentDefinition(mappedInterceptorDef, beanName));
    }

    context.popAndRegisterContainingComponent();
    return null;
}

4.2.2. 加载拦截器

在RequestMappingHandlerMapping中的初始化上下文中，会加载拦截器

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public final void setApplicationContext(@Nullable ApplicationContext context) throws BeansException {
    if (context == null && !isContextRequired()) {
        //......
    }
    else if (this.applicationContext == null) {
        //......
        //初始化上下文
        initApplicationContext(context);
    }
    else {
        //......
    }
}
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protected void initApplicationContext(ApplicationContext context) {
    // 初始化
    super.initApplicationContext(context);
    if (this.servletContext == null && context instanceof WebApplicationContext) {
        this.servletContext = ((WebApplicationContext) context).getServletContext();
        if (this.servletContext != null) {
            initServletContext(this.servletContext);
        }
    }
}
protected void initApplicationContext(ApplicationContext context) throws BeansException {
    initApplicationContext();
}
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@Override
protected void initApplicationContext() throws BeansException {
    //空方法，扩展使用
    extendInterceptors(this.interceptors);
    //从容器中解析出MappedInterceptor
    detectMappedInterceptors(this.adaptedInterceptors);
    //初始化拦截器
    initInterceptors();
}
// 初始化拦截器
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");
            }
            //加入拦截器组
            this.adaptedInterceptors.add(adaptInterceptor(interceptor));
        }
    }
}
//转换拦截器，主要转换 WebRequestInterceptor
protected HandlerInterceptor adaptInterceptor(Object interceptor) {
    if (interceptor instanceof HandlerInterceptor) {
        return (HandlerInterceptor) interceptor;
    }
    else if (interceptor instanceof WebRequestInterceptor) {
        // 转换WebRequestInterceptor
        return new WebRequestHandlerInterceptorAdapter((WebRequestInterceptor) interceptor);
    }
    else {
        throw new IllegalArgumentException("Interceptor type not supported: " + interceptor.getClass().getName());
    }
}

5. 总结

专门拿一个解析器解析拦截器，注册成BeanDifinition，再通过获取容器Bean，加入到RequestMappingHandlerMapping中

6. 注意事项