本篇文章篇幅比较长，但是细看下去相信对学习Shiro应该会有帮助。好了，闲话不多说，直接进入正题：
Shiro提供了与Web集成的支持，其通过一个ShiroFilter入口来拦截需要安全控制的URL，然后进行相应的控制，ShiroFilter类似于如Strut2/SpringMVC这种web框架的前端控制器，其是安全控制的入口点，其负责读取配置（如ini配置文件），然后判断URL是否需要登录/权限等工作。
而要在spring中使用Shiro的话，可在web.xml中配置一个DelegatingFilterProxy，DelegatingFilterProxy作用是自动到Spring容器查找名字为shiroFilter（filter-name）的bean并把所有Filter的操作委托给它。
首先是在web.xml中配置DelegatingFilterProxy
<filter> <filter-name>shiroFilter</filter-name> <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class> <init-param> <param-name>targetFilterLifecycle</param-name> <param-value>true</param-value> </init-param> </filter> <filter-mapping> <filter-name>shiroFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> 123456789101112 123456789101112配置好DelegatingFilterProxy后，下面只要再把ShiroFilter配置到Spring容器（此处为Spring的配置文件）即可：
<bean id="shiroFilter" class="org.apache.shiro.spring.web.ShiroFilterFactoryBean"> <property name="securityManager" ref="securityManager"/> </bean> 123 123可以看到我们使用了ShiroFilterFactoryBean来创建shiroFilter，这里用到了Spring中一种特殊的Bean——FactoryBean。当需要得到名为”shiroFilter“的bean时，会调用其getObject()来获取实例。下面我们通过分析ShiroFilterFactoryBean创建实例的过程来探究Shiro是如何实现安全拦截的：
public Object getObject() throws Exception { if (instance == null) { instance = createInstance(); } return instance; } 123456 123456其中调用了createInstance()来创建实例：
protected AbstractShiroFilter createInstance() throws Exception { // 这里是通过FactoryBean注入的SecurityManager（必须） SecurityManager securityManager = getSecurityManager(); if (securityManager == null) { String msg = "SecurityManager property must be set."; throw new BeanInitializationException(msg); } if (!(securityManager instanceof WebSecurityManager)) { String msg = "The security manager does not implement the WebSecurityManager interface."; throw new BeanInitializationException(msg); } FilterChainManager manager = createFilterChainManager(); PathMatchingFilterChainResolver chainResolver = new PathMatchingFilterChainResolver(); chainResolver.setFilterChainManager(manager); return new SpringShiroFilter((WebSecurityManager) securityManager, chainResolver); } 123456789101112131415161718192021 123456789101112131415161718192021可以看到创建SpringShiroFilter时用到了两个组件：SecurityManager和ChainResolver。
SecurityManager：我们知道其在Shiro中的地位，类似于一个“安全大管家”，相当于SpringMVC中的DispatcherServlet或者Struts2中的FilterDispatcher，是Shiro的心脏，所有具体的交互都通过SecurityManager进行控制，它管理着所有Subject、且负责进行认证和授权、及会话、缓存的管理。ChainResolver：Filter链解析器，用来解析出该次请求需要执行的Filter链。PathMatchingFilterChainResolver：ChainResolver的实现类，其中还包含了两个重要组件FilterChainManager、PatternMatcherFilterChainManager：管理着Filter和Filter链，配合PathMatchingFilterChainResolver解析出Filter链PatternMatcher：用来进行请求路径匹配，默认为Ant风格的路径匹配先有一个大体的了解，那么对于源码分析会有不少帮助。下面会对以上两个重要的组件进行分析，包括PathMatchingFilterChainResolver和FilterChainManager。首先贴一段ShiroFilter的在配置文件中的定义：
<!-- Shiro的Web过滤器 --> <bean id="shiroFilter" class="org.apache.shiro.spring.web.ShiroFilterFactoryBean"> <property name="securityManager" ref="securityManager" /> <property name="loginUrl" value="/login" /> <property name="unauthorizedUrl" value="/special/unauthorized" /> <property name="filters"> <util:map> <entry key="authc" value-ref="formAuthenticationFilter" /> <entry key="logout" value-ref="logoutFilter" /> <entry key="ssl" value-ref="sslFilter"></entry> </util:map> </property> <property name="filterChainDefinitions"> <value> /resources/** = anon /plugin/** = anon /download/** = anon /special/unauthorized = anon /register = anon /login = ssl,authc /logout = logout /admin/** = roles[admin] /** = user </value> </property> </bean> 12345678910111213141516171819202122232425262728 12345678910111213141516171819202122232425262728再来看看PathMatchingFilterChainResolver和FilterChainManager的创建过程：
protected FilterChainManager createFilterChainManager() { // 默认使用的FilterChainManager是DefaultFilterChainManager DefaultFilterChainManager manager = new DefaultFilterChainManager(); // DefaultFilterChainManager默认会注册的filters(后面会列出) Map<String, Filter> defaultFilters = manager.getFilters(); // 将ShiroFilterFactoryBean配置的一些公共属性(上面配置的loginUrl,successUrl,unauthorizeUrl)应用到默认注册的filter上去 for (Filter filter : defaultFilters.values()) { applyGlobalPropertiesIfNecessary(filter); } // 处理自定义的filter（上面配置的filters属性），步骤类似上面 Map<String, Filter> filters = getFilters(); if (!CollectionUtils.isEmpty(filters)) { for (Map.Entry<String, Filter> entry : filters.entrySet()) { String name = entry.getKey(); Filter filter = entry.getValue(); applyGlobalPropertiesIfNecessary(filter); if (filter instanceof Nameable) { ((Nameable) filter).setName(name); } // 将Filter添加到manager中去，可以看到对于Filter的管理是依赖于FilterChainManager的 manager.addFilter(name, filter, false); } } // 根据FilterChainDefinition的配置来构建Filter链（上面配置的filterChainDefinitions属性） Map<String, String> chains = getFilterChainDefinitionMap(); if (!CollectionUtils.isEmpty(chains)) { for (Map.Entry<String, String> entry : chains.entrySet()) { String url = entry.getKey(); String chainDefinition = entry.getValue(); // 后面会分析该步的源码，功能上就是创建Filter链 manager.createChain(url, chainDefinition); } } return manager; } 12345678910111213141516171819202122232425262728293031323334353637383940 12345678910111213141516171819202122232425262728293031323334353637383940下面有必要来看看DefaultFilterChainManager的源码，分析一下上面调用到的方法。先来看看他的几个重要的属性：
private FilterConfig filterConfig; private Map<String, Filter> filters; //pool of filters available for creating chains private Map<String, NamedFilterList> filterChains; //key: chain name, value: chain 12345 12345其中filterConfig仅在初始化Filter时有效，而我们自定义的Filter都不是init的，所以该属性可以暂时忽略（）。 而后面两张map就重要了：filters中缓存了所有添加的filter，filterChains则缓存了所有的filterChain。其中前者的key是filter name，value是Filter。而后者的key是chain name，value是NamedFilterList。 有的童鞋可能会问NamedFilterList是怎么样的结构呢，你可以把它当成List<Filter>，这样就好理解了吧。下面再分析刚才createFilterChainManager()中调用过的manager的几个方法：
addFilter（缓存filter让manager来管理） public void addFilter(String name, Filter filter, boolean init) { addFilter(name, filter, init, true); } protected void addFilter(String name, Filter filter, boolean init, boolean overwrite) { Filter existing = getFilter(name); if (existing == null || overwrite) { if (filter instanceof Nameable) { ((Nameable) filter).setName(name); } if (init) { initFilter(filter); } this.filters.put(name, filter); } } 12345678910111213141516 12345678910111213141516将filter缓存到filters这张map里，不管是默认注册的还是自定义的都需要FilterChainManager来统一管理。
createChain：创建filterChain并将定义的filter都加进去 // chainName就是拦截路径"/resources/**"，chainDefinition就是多个过滤器名的字符串 public void createChain(String chainName, String chainDefinition) { if (!StringUtils.hasText(chainName)) { throw new NullPointerException("chainName cannot be null or empty."); } if (!StringUtils.hasText(chainDefinition)) { throw new NullPointerException("chainDefinition cannot be null or empty."); } if (log.isDebugEnabled()) { log.debug("Creating chain [" + chainName + "] from String definition [" + chainDefinition + "]"); } // 先分离出配置的各个filter，比如 // "authc, roles[admin,user], perms[file:edit]" 分离后的结果是： // { "authc", "roles[admin,user]", "perms[file:edit]" } String[] filterTokens = splitChainDefinition(chainDefinition); // 进一步分离出"[]"内的内容，其中nameConfigPair是一个长度为2的数组 // 比如 roles[admin,user] 经过解析后的nameConfigPair 为{"roles", "admin,user"} for (String token : filterTokens) { String[] nameConfigPair = toNameConfigPair(token); // 得到了 拦截路径、filter以及可能的"[]"中的值，那么执行addToChain addToChain(chainName, nameConfigPair[0], nameConfigPair[1]); } } 123456789101112131415161718192021222324252627 123456789101112131415161718192021222324252627 addToChain public void addToChain(String chainName, String filterName, String chainSpecificFilterConfig) { if (!StringUtils.hasText(chainName)) { throw new IllegalArgumentException("chainName cannot be null or empty."); } Filter filter = getFilter(filterName); if (filter == null) { throw new IllegalArgumentException("There is no filter with name '" + filterName + "' to apply to chain [" + chainName + "] in the pool of available Filters. Ensure a " + "filter with that name/path has first been registered with the addFilter method(s)."); } // 将匹配关系注册到filter中，后续会提到 applyChainConfig(chainName, filter, chainSpecificFilterConfig); // 确保chain已经被加到filterChains这张map中了 NamedFilterList chain = ensureChain(chainName); // 将该filter加入当前chain chain.add(filter); } 1234567891011121314151617 1234567891011121314151617至此，FilterChainManager就创建完了，它无非就是缓存了两张map，没有什么逻辑上的操作。下面将FilterChainManager设置到PathMatchingFilterChainResolver中。PathMatchingFilterChainResolver实现了FilterChainResolver接口，该接口中只定义了一个方法：
FilterChain getChain(ServletRequest request, ServletResponse response, FilterChain originalChain); 1 1通过解析请求来得到一个新的FilterChain。而PathMatchingFilterChainResolver实现了该接口，依靠了FilterChainManager中保存的chainFilters和filters这两张map来根据请求路径解析出相应的filterChain，并且和originalChain组合起来使用。下面具体看看PathMatchingFilterChainResolver中的实现：
public FilterChain getChain(ServletRequest request, ServletResponse response, FilterChain originalChain) { // 得到 FilterChainManager FilterChainManager filterChainManager = getFilterChainManager(); if (!filterChainManager.hasChains()) { return null; } String requestURI = getPathWithinApplication(request); // chainNames就是刚定义的filterChains的keySet，也就是所有的路径集合(比如：["/resources/**","/login"]) for (String pathPattern : filterChainManager.getChainNames()) { // 请求路径是否匹配某个 定义好的路径: if (pathMatches(pathPattern, requestURI)) { if (log.isTraceEnabled()) { log.trace("Matched path pattern [" + pathPattern + "] for requestURI [" + requestURI + "]. " + "Utilizing corresponding filter chain..."); } // 找到第一个匹配的Filter链，那么就返回一个ProxiedFilterChain return filterChainManager.proxy(originalChain, pathPattern); } } return null; } 123456789101112131415161718192021222324 123456789101112131415161718192021222324这里返回只有两种情况，要么是null，要么就是一个ProxiedFilterChain。返回null并不表示中断FilterChain，而是只用originChain。而关于ProxiedFilterChain，它实现了FilterChain，内部维护了两份FilterChain（其实一个是FilterChain，另一个是List<Filter>） FilterChain也就是web.xml中注册的Filter形成的FilterChain，我们称之为originChain。而另一个List<Filter>则是我们在Shiro中注册的Filter链了，下面看看ProxiedFilterChain中关于doFilter(...)的实现：
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); } else { if (log.isTraceEnabled()) { log.trace("Invoking wrapped filter at index [" + this.index + "]"); } this.filters.get(this.index++).doFilter(request, response, this); } } 1234567891011121314 1234567891011121314可以看到，它会先执行Shiro中执行的filter，然后再执行web.xml中的Filter。不过要注意的是，需要等到originChain执行到ShiroFilter之后才会执行Shiro中的Filter链。 至此，两个组件的创建过程差不多都介绍完了，那么当这两个组件创建完毕后，是如何工作的呢？ 先从ShiroFilter入手，因为它是总的拦截器，看看其中的doFilterInternal(...)方法：
protected void doFilterInternal(ServletRequest servletRequest, ServletResponse servletResponse, final FilterChain chain) throws ServletException, IOException { Throwable t = null; try { final ServletRequest request = prepareServletRequest(servletRequest, servletResponse, chain); final ServletResponse response = prepareServletResponse(request, servletResponse, chain); final Subject subject = createSubject(request, response); //noinspection unchecked subject.execute(new Callable() { public Object call() throws Exception { // 其实需要关心的就在这里 // touch一下session updateSessionLastAccessTime(request, response); // 执行Filter链 executeChain(request, response, chain); return null; } }); } catch (ExecutionException ex) { t = ex.getCause(); } catch (Throwable throwable) { t = throwable; } if (t != null) { if (t instanceof ServletException) { throw (ServletException) t; } if (t instanceof IOException) { throw (IOException) t; } //otherwise it's not one of the two exceptions expected by the filter method signature - wrap it in one: String msg = "Filtered request failed."; throw new ServletException(msg, t); } } 12345678910111213141516171819202122232425262728293031323334353637383940 12345678910111213141516171819202122232425262728293031323334353637383940跟进executeChain(...)方法：
protected void executeChain(ServletRequest request, ServletResponse response, FilterChain origChain) throws IOException, ServletException { FilterChain chain = getExecutionChain(request, response, origChain); chain.doFilter(request, response); } 12345 12345如何得到FilterChain的呢？如果你认真的看到这里，那么你应该不难想到其中肯定利用了刚才注册的ChainResolver：
protected FilterChain getExecutionChain(ServletRequest request, ServletResponse response, FilterChain origChain) { FilterChain chain = origChain; FilterChainResolver resolver = getFilterChainResolver(); if (resolver == null) { log.debug("No FilterChainResolver configured. Returning original FilterChain."); return origChain; } FilterChain resolved = resolver.getChain(request, response, origChain); if (resolved != null) { log.trace("Resolved a configured FilterChain for the current request."); chain = resolved; } else { log.trace("No FilterChain configured for the current request. Using the default."); } return chain; } 12345678910111213141516171819 12345678910111213141516171819猜对了~并且也验证了当resolver.getChain(...)返回null时，直接使用originChain了。然后执行返回的FilterChain的doFilter(...)方法。这个过程我们再脱离代码来分析一下：当我们从浏览器发出一个请求，究竟发生了什么？ 这里只站在Filter的层面来分析。服务器启动后，读取web.xml中的filter、filter-mapping节点后组成FilterChain，对请求进行拦截。拦截的顺序按照filter节点的定义顺序，Shiro利用ShiroFilter来充当一个总的拦截器来分发所有需要被Shiro拦截的请求，所以我们看到在Shiro中我们还可以自定义拦截器。ShiroFilter根据它在拦截器中的位置，只要执行到了那么就会暂时中断原FilterChain的执行，先执行Shiro中定义的Filter，最后再执行原FilterChian。可以打个比方，比如说本来有一条铁链，一直蚂蚁从铁链的开端往末端爬，其中某一环叫ShiroFilter，那么当蚂蚁爬到ShiroFilter这一环时，将铁链打断，并且接上另一端铁链（Shiro中自定义的Filter），这样就构成了一条新的铁链。然后蚂蚁继续爬行（后续的执行过程）。
到这里，我们已经根据请求路径找到了一条Filter链（originChain + shiroChain），之后就是对链上的Filter做doFilter，其中关于如何 就是filter后配置的[]部分是如何生效的，我们可以看PathMatchingFilter中的Prehandle(...)方法：
protected boolean preHandle(ServletRequest request, ServletResponse response) throws Exception { if (this.appliedPaths == null || this.appliedPaths.isEmpty()) { if (log.isTraceEnabled()) { log.trace("appliedPaths property is null or empty. This Filter will passthrough immediately."); } return true; } // appliedPaths中保存了该filter中能拦截的路径和该路径配置的key-value对，比如{key="/admin/**", value="[admin]"} for (String path : this.appliedPaths.keySet()) { // 首先是匹配路径 if (pathsMatch(path, request)) { log.trace("Current requestURI matches pattern '{}'. Determining filter chain execution...", path); // 然后开始验证“[]”中的字符串 Object config = this.appliedPaths.get(path); return isFilterChainContinued(request, response, path, config); } } //no path matched, allow the request to go through: return true; } 1234567891011121314151617181920212223 1234567891011121314151617181920212223下面跟踪isFilterChainContinued(...)：
private boolean isFilterChainContinued(ServletRequest request, ServletResponse response, String path, Object pathConfig) throws Exception { if (isEnabled(request, response, path, pathConfig)) { //isEnabled check added in 1.2 if (log.isTraceEnabled()) { // log } return onPreHandle(request, response, pathConfig); } if (log.isTraceEnabled()) { // log } return true; } 123456789101112131415 123456789101112131415基本也就是交给onPreHandle(...)来处理，所以一般需要验证”[]“中字符串的filter都会扩展这个方法，比如AccessControlFilter：
public boolean onPreHandle(ServletRequest request, ServletResponse response, Object mappedValue) throws Exception { return isAccessAllowed(request, response, mappedValue) || onAccessDenied(request, response, mappedValue); } 123 123而RolesAuthorizationFilter中：
public boolean isAccessAllowed(ServletRequest request, ServletResponse response, Object mappedValue) throws IOException { Subject subject = getSubject(request, response); String[] rolesArray = (String[]) mappedValue; if (rolesArray == null || rolesArray.length == 0) { //no roles specified, so nothing to check - allow access. return true; } Set<String> roles = CollectionUtils.asSet(rolesArray); return subject.hasAllRoles(roles); } 12345678910111213 12345678910111213最后附上默认注册的filters：
public enum DefaultFilter { 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); } 1234567891011121314 1234567891011121314水平有限，写得蛮不容易，看源码加写花了整整2天。希望对大家能有帮助~
