shiro原始碼篇 - shiro的filter，你值得擁有

摘要： 前言 開心一刻 已經報廢了一年多的電腦，今天特麼突然開機了，嚇老子一跳，只見電腦管家緩緩地出來了，本次開機一共用時一年零六個月，打敗了全國0%的電腦，電腦管家已經對您的電腦失去信心，然後它把自己解除安裝了，只剩我在一旁發呆。 路漫漫其修遠兮，吾將上下而求索！ git...

前言

開心一刻

已經報廢了一年多的電腦，今天特麼突然開機了，嚇老子一跳，只見電腦管家緩緩地出來了，本次開機一共用時一年零六個月，打敗了全國0%的電腦，電腦管家已經對您的電腦失去信心，然後它把自己解除安裝了，只剩我在一旁發呆。

路漫漫其修遠兮，吾將上下而求索！

github： ofollow,noindex"> https://github.com/youzhibing

碼雲(gitee)： https://gitee.com/youzhibing

shiroFilter的註冊

此篇博文 講到了springboot的filter註冊，但只是filter註冊的一種方式：通過FilterRegistrationBean實現。而Shiro Filter的註冊是採用另外的方式實現的，我們接著往下看

ShiroFilterFactoryBean實現了FactoryBean，我們來看下ShiroFilterFactoryBean對FactoryBean的getObject方法的實現

git圖一

可以看到createInstance()返回的是SpringShiroFilter的例項；SpringShiroFilter的類圖如下

getObject方法只是建立了一個SpringShiroFilter例項，並註冊到了spring容器中，那是如何註冊到servlet容器的呢？我們來跟下原始碼

這篇博文 其實涉及到了，只是那時候沒細講，我們還是從那裡開始

gif圖二

ServletContextInitializerBeans.java的構造方法，裡面有addServletContextInitializerBeans(beanFactory)方法和addAdaptableBeans(beanFactory)，我們來好好瞅一瞅

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);
}
}

View Code

會將spring bean工廠（beanFactory）中型別是ServletContextInitalizer型別的例項（包括ServletRegistrationBean、FilterRegistrationBean、DelegatingFilterProxyRegistrationBean、ServletListenerRegistrationBean）新增進ServletContextInitializerBeans的initializers屬性中。

private final MultiValueMap<Class<?>, ServletContextInitializer> initializers;

ServletContextInitalizer的子類圖如下所示

這也就是 上篇博文 註冊Filter的方式，以RegistrationBean方式實現的， 但是SpringShiroFilter不是在這新增進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());
}
}

View Code

會將beanFactory中的Servlet、Filter、Listener例項封裝成對應的RegistrationBean，然後新增到ServletContextInitializerBeans的initializers；部分細節沒去跟，有興趣的可以自行去跟下原始碼。

ServletContextInitializerBeans的sortedList的內容最終如下

然後遍歷這個sortedList，逐個注入到servlet容器

小結

springboot下有3種方式註冊Filter（Servlet、Listener類似），FilterRegistrationBean、@WebFilter 和@Bean，@WebFilter我還沒試過，另外這3種方式註冊的Filter的優先順序是：FilterRegistrationBean > @WebFilter > @Bean（網上查閱的資料，我沒試哦，使用過程中需要注意！）。

不管是FilterRegistrationBean方式、@WebFilter方式，還是@Bean方式，只要是受spring容器管理，最終都會新增到ServletContextInitializerBeans的initializers中，都會成功註冊到servlet容器。@WebFilter方式和@Bean方式註冊的Filter都會被封裝成FilterRegistrationBean，然後新增進ServletContextInitializerBeans的initializers；3中方式最終殊途同歸，都以FilterRegistrationBean的形式存在ServletContextInitializerBeans的initializers中。SpringShiroFilter的註冊算是@Bean方式註冊的，至此SpringShiroFilter就註冊到了servlet容器中了。

ServletContextInitializerBeans的sortedList如下：

private List<ServletContextInitializer> sortedList;

是一個有序的ServletContextInitializer List，這個有序針對的同類型，比如所有的FilterRegistrationBean有序，所有的ServletRegistrationBean有序，FilterRegistrationBean與ServletRegistrationBean之間有沒有序是無意義的。

shiro中的Filter鏈

shiro的預設filter列表

除了SpringShiroFilter之外，shiro還有預設的11個Filter；細心的朋友應該在git圖一中已經發現了，在建立DefaultFilterChainManager，就把預設的11個Filter新增到它的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);// 將預設的11個Filter新增到filters
}

這11個Filter具體如下

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鏈

SpringShiroFilter註冊到servlet容器中，請求肯定會經過SpringShiroFilter的doFilter方法，我們就從此開始跟一跟原始碼

gif圖三

上圖中可能展示的不夠細，主要就是兩點：1、路徑匹配：pathMatches(pathPattern, requestURI)，預設的Fliter逐個與請求URI進行匹配；2、代理FilterChain：ProxiedFilterChain。如果匹配不上，那麼直接走servlet的FilterChain，否則先走shiro的代理FilterChain（ProxiedFilterChain），之後再走servlet的FilterChain。

ProxiedFilterChain原始碼如下

/*
 * 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預設的11個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);// 當shiro的11個Filter走完之後，繼續走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);// 遞迴逐個走shiro的11個Filter
}
}
}

View Code

Shiro對Servlet容器的FilterChain進行了代理，即ShiroFilter在繼續Servlet容器的Filter鏈的執行之前，通過ProxiedFilterChain對Servlet容器的FilterChain進行了代理；即先走Shiro自己的Filter體系，然後才會委託給Servlet容器的FilterChain進行Servlet容器級別的Filter鏈執行；Shiro的ProxiedFilterChain執行流程：1、先執行Shiro自己的Filter鏈；2、再執行Servlet容器的Filter鏈（即原始的 Filter）。

總結

1、SpringShiroFilter註冊到spring容器，會被包裝成FilterRegistrationBean，通過FilterRegistrationBean註冊到servlet容器；

2、一般而言，shiro的PathMatchingFilterChainResolver會匹配所有的請求，Shiro對Servlet容器的FilterChain進行了代理，生成代理FilterChain：ProxiedFilterChain，請求先走Shiro自己的Filter鏈，再走Servelt容器的Filter鏈；

3、題外話，springboot註冊Filter、Servlet、Listener方式類似，都有3種，具體是哪三種，大家去上文看；關於Shiro的Filter，本文沒做更詳細的講解，需要了解的可以去看《跟我學shiro》

參考

《跟我學shiro》

shiro原始碼