shiro源码篇 - shiro的filter，你值得拥有
开心一刻
已经报废了一年多的电脑，今天特么突然开机了，吓老子一跳
只见电脑管家缓缓地出来了，本次开机一共用时一年零六个月，打败了全国0%的电脑，电脑管家已经对您的电脑失去信心，然后它把自己卸载了，只剩我在一旁发呆
shiroFilter的注册
此篇博文讲到了springboot的filter注册，但只是filter注册的一种方式：通过FilterRegistrationBean实现。而Shiro Filter的注册是采用另外的方式实现的，我们接着往下看
ShiroFilterFactoryBean实现了FactoryBean，我们来看下ShiroFilterFactoryBean对FactoryBean的getObject方法的实现
git图一
可以看到createInstance()返回的是SpringShiroFilter的实例；SpringShiroFilter的类图如下
getObject方法只是创建了一个SpringShiroFilter实例，并注册到了spring容器中，那是如何注册到servlet容器的呢？我们来跟下源码
这篇博文其实涉及到了，只是那时候没细讲，我们还是从那里开始
gif图二
ServletContextInitializerBeans.java的构造方法，里面有addServletContextInitializerBeans(beanFactory)方法和addAdaptableBeans(beanFactory)，我们来好好瞅一瞅
addServletContextInitializerBeans(beanFactory)
private void addServletContextInitializerBeans(ListableBeanFactory beanFactory) { for (Entry<String, ServletContextInitializer> initializerBean : getOrderedBeansOfType( beanFactory, ServletContextInitializer.class)) { addServletContextInitializerBean(initializerBean.getKey(), initializerBean.getValue(), beanFactory); } } private void addServletContextInitializerBean(String beanName, ServletContextInitializer initializer, ListableBeanFactory beanFactory) { if (initializer instanceof ServletRegistrationBean) { Servlet source = ((ServletRegistrationBean<?>) initializer).getServlet(); addServletContextInitializerBean(Servlet.class, beanName, initializer, beanFactory, source); } else if (initializer instanceof FilterRegistrationBean) { Filter source = ((FilterRegistrationBean<?>) initializer).getFilter(); addServletContextInitializerBean(Filter.class, beanName, initializer, beanFactory, source); } else if (initializer instanceof DelegatingFilterProxyRegistrationBean) { String source = ((DelegatingFilterProxyRegistrationBean) initializer) .getTargetBeanName(); addServletContextInitializerBean(Filter.class, beanName, initializer, beanFactory, source); } else if (initializer instanceof ServletListenerRegistrationBean) { EventListener source = ((ServletListenerRegistrationBean<?>) initializer) .getListener(); addServletContextInitializerBean(EventListener.class, beanName, initializer, beanFactory, source); } else { addServletContextInitializerBean(ServletContextInitializer.class, beanName, initializer, beanFactory, initializer); } }
会将spring bean工厂（beanFactory）中类型是ServletContextInitalizer类型的实例（包括ServletRegistrationBean、FilterRegistrationBean、DelegatingFilterProxyRegistrationBean、ServletListenerRegistrationBean）添加进ServletContextInitializerBeans的initializers属性中。
private final MultiValueMap<Class<?>, ServletContextInitializer> initializers;
ServletContextInitalizer的子类图如下所示
这也就是上篇博文注册Filter的方式，以RegistrationBean方式实现的，但是SpringShiroFilter不是在这添加进ServletContextInitializerBeans的initializers中的哦
addAdaptableBeans(beanFactory)
private void addAdaptableBeans(ListableBeanFactory beanFactory) { MultipartConfigElement multipartConfig = getMultipartConfig(beanFactory); addAsRegistrationBean(beanFactory, Servlet.class, new ServletRegistrationBeanAdapter(multipartConfig)); addAsRegistrationBean(beanFactory, Filter.class, new FilterRegistrationBeanAdapter()); for (Class<?> listenerType : ServletListenerRegistrationBean .getSupportedTypes()) { addAsRegistrationBean(beanFactory, EventListener.class, (Class<EventListener>) listenerType, new ServletListenerRegistrationBeanAdapter()); } }
会将beanFactory中的Servlet、Filter、Listener实例封装成对应的RegistrationBean，然后添加到ServletContextInitializerBeans的initializers；部分细节没去跟，有兴趣的可以自行去跟下源代码。
ServletContextInitializerBeans的sortedList的内容最终如下
然后遍历这个sortedList，逐个注入到servlet容器
小结
springboot下有3种方式注册Filter（Servlet、Listener类似），FilterRegistrationBean、@WebFilter 和@Bean，@WebFilter我还没试过，另外这3种方式注册的Filter的优先级是：FilterRegistrationBean > @WebFilter > @Bean（网上查阅的资料，我没试哦，使用过程中需要注意！）。
不管是FilterRegistrationBean方式、@WebFilter方式，还是@Bean方式，只要是受spring容器管理，最终都会添加到ServletContextInitializerBeans的initializers中，都会成功注册到servlet容器。@WebFilter方式和@Bean方式注册的Filter都会被封装成FilterRegistrationBean，然后添加进ServletContextInitializerBeans的initializers；3种方式最终殊途同归，都以FilterRegistrationBean的形式存在ServletContextInitializerBeans的initializers中。SpringShiroFilter的注册算是@Bean方式注册的，至此SpringShiroFilter就注册到了servlet容器中了。
ServletContextInitializerBeans的sortedList如下：
private List<ServletContextInitializer> sortedList;
是一个有序的ServletContextInitializer List，这个有序针对的同类型，比如所有的FilterRegistrationBean有序，所有的ServletRegistrationBean有序，FilterRegistrationBean与ServletRegistrationBean之间有没有序是无意义的。
shiro中的Filter链
shiro的默认filter列表
除了SpringShiroFilter之外，shiro还有默认的11个Filter；细心的朋友应该在git图一中已经发现了，在创建DefaultFilterChainManager，就把默认的11个Filter添加到它的filters中
private Map<String, Filter> filters; //pool of filters available for creating chains private Map<String, NamedFilterList> filterChains; //key: chain name, value: chain public DefaultFilterChainManager() { this.filters = new LinkedHashMap<String, Filter>(); this.filterChains = new LinkedHashMap<String, NamedFilterList>(); addDefaultFilters(false); // 将默认的11个Filter添加到filters }
这11个Filter具体如下
anon(AnonymousFilter.class), authc(FormAuthenticationFilter.class), authcBasic(BasicHttpAuthenticationFilter.class), logout(LogoutFilter.class), noSessionCreation(NoSessionCreationFilter.class), perms(PermissionsAuthorizationFilter.class), port(PortFilter.class), rest(HttpMethodPermissionFilter.class), roles(RolesAuthorizationFilter.class), ssl(SslFilter.class), user(UserFilter.class);
Filter链
SpringShiroFilter注册到servlet容器中，请求肯定会经过SpringShiroFilter的doFilter方法，我们就从此开始跟一跟源代码
gif图三
上图中可能展示的不够细，主要就是两点：1、路径匹配：pathMatches(pathPattern, requestURI)，默认的Fliter逐个与请求URI进行匹配；2、代理FilterChain：ProxiedFilterChain。如果匹配不上，那么直接走servlet的FilterChain，否则先走shiro的代理FilterChain（ProxiedFilterChain），之后再走servlet的FilterChain。
ProxiedFilterChain源代码如下
/* * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, * software distributed under the License is distributed on an * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY * KIND, either express or implied. See the License for the * specific language governing permissions and limitations * under the License. */ package org.apache.shiro.web.servlet; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import javax.servlet.*; import java.io.IOException; import java.util.List; /** * A proxied filter chain is a {@link FilterChain} instance that proxies an original {@link FilterChain} as well * as a {@link List List} of other {@link Filter Filter}s that might need to execute prior to the final wrapped * original chain. It allows a list of filters to execute before continuing the original (proxied) * {@code FilterChain} instance. * * @since 0.9 */ public class ProxiedFilterChain implements FilterChain { //TODO - complete JavaDoc private static final Logger log = LoggerFactory.getLogger(ProxiedFilterChain.class); private FilterChain orig; // 原FilterChain，也就是servlet容器的FilterChain private List<Filter> filters; // shiro默认的11个Filter private int index = 0; public ProxiedFilterChain(FilterChain orig, List<Filter> filters) { if (orig == null) { throw new NullPointerException("original FilterChain cannot be null."); } this.orig = orig; this.filters = filters; this.index = 0; } public void doFilter(ServletRequest request, ServletResponse response) throws IOException, ServletException { if (this.filters == null || this.filters.size() == this.index) { //we've reached the end of the wrapped chain, so invoke the original one: if (log.isTraceEnabled()) { log.trace("Invoking original filter chain."); } this.orig.doFilter(request, response); // 当shiro的11个Filter走完之后，继续走servlet容器的FilterChain } else { if (log.isTraceEnabled()) { log.trace("Invoking wrapped filter at index [" + this.index + "]"); } this.filters.get(this.index++).doFilter(request, response, this); // 递归逐个走shiro的11个Filter } } }
Shiro对Servlet容器的FilterChain进行了代理，即ShiroFilter在继续Servlet容器的Filter链的执行之前，通过ProxiedFilterChain对Servlet容器的FilterChain进行了代理；即先走Shiro自己的Filter体系，然后才会委托给Servlet容器的FilterChain进行Servlet容器级别的Filter链执行；Shiro的ProxiedFilterChain执行流程：1、先执行Shiro自己的Filter链；2、再执行Servlet容器的Filter链（即原始的 Filter）。
总结
1、SpringShiroFilter注册到spring容器，会被包装成FilterRegistrationBean，通过FilterRegistrationBean注册到servlet容器；
2、一般而言，shiro的PathMatchingFilterChainResolver会匹配所有的请求，Shiro对Servlet容器的FilterChain进行了代理，生成代理FilterChain：ProxiedFilterChain，请求先走Shiro自己的Filter链，再走Servelt容器的Filter链；
3、题外话，springboot注册Filter、Servlet、Listener方式类似，都有3种，具体是哪三种，大家去上文看；关于Shiro的Filter，本文没做更详细的讲解，需要了解的可以去看《跟我学shiro》
参考
《跟我学shiro》
shiro源码
