【Java源码】— Shiro的ShiroFilterFactoryBean源码解析
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>shiroFilterfilter-name>
<filter-class>org.springframework.web.filter.DelegatingFilterProxyfilter-class>
param>
<param-name>targetFilterLifecycleparam-name>
<param-value>trueparam-value>
param>
filter>
<filter-mapping>
<filter-name>shiroFilterfilter-name>
/*
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：
id="shiroFilter" class="org.apache.shiro.spring.web.ShiroFilterFactoryBean">
<property name="securityManager" ref="securityManager"/>
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;
}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);
}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：
<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>
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;
}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，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);
}
}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]);
}
}- 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);
}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
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;
}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） 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);
}
}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);
}
}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);
}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;
}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;
}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;
}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);
}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 roles = CollectionUtils.asSet(rolesArray);
return subject.hasAllRoles(roles);
} 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);
}