Shiro源码分析----认证流程

Posted 2021-03-28 Java精讲

由于本文是基于源码分析Shiro认证流程，所以假设阅读者对Shiro已经有一定的了解。

Apache Shiro作为一个优秀的权限框架，其最重要的两项工作：其一是认证，即解决登录的用户的身份是否合法；其二是用户登录后有什么样的权限。本文将基于Shiro源码来剖析Shiro的认证流程，只有深层次的理解Shiro认证流程，认证过程中各个组件的作用，才能在实际应用中灵活使用。由于Shiro一般用于Web环境且会与Spring集成使用，所以此次认证流程的分析的前提也是Web环境且Shiro已与Spring集成。

特别说明：本文使用的Shiro版本：1.2.2。

Shiro与Spring集成时，需要在web.xml中配置Shiro入口过滤器：

<filter> <filter-name>shiroFilter</filter-name> <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class> <async-supported>true</async-supported> <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>

熟悉Spring的人应该都知道DelegatingFilterProxy的作用，该Spring提供的过滤器只起委托作用，执行流程委托给Spring容器中名为shiroFilter的过滤器。所以还需要在Spring配置文件中配置shiroFilter，如下:

<!-- 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.jsp"/> <property name="unauthorizedUrl" value="/unauthorized.jsp"/> <property name="filters"> <util:map> <entry key="authc" value-ref="formAuthenticationFilter"/> </util:map> </property> <property name="filterChainDefinitions"> <value> /index.jsp = anon /unauthorized.jsp = anon /login.jsp = authc /logout = logout /authenticated.jsp = authc  /** = user </value> </property></bean>

ShiroFilterFactoryBean实现了org.springframework.beans.factory.FactoryBean接口，所以shiroFilter对象是由ShiroFilterFactoryBean的getObject()方法返回的：

public Object getObject() throws Exception { if (instance == null) { instance = createInstance(); } return instance;} protected AbstractShiroFilter createInstance() throws Exception {  log.debug("Creating Shiro Filter instance."); // 获取配置文件中设置的安全管理器 SecurityManager securityManager = getSecurityManager(); if (securityManager == null) { String msg = "SecurityManager property must be set."; throw new BeanInitializationException(msg); } // 必须是Web环境的安全管理器 if (!(securityManager instanceof WebSecurityManager)) { String msg = "The security manager does not implement the WebSecurityManager interface."; throw new BeanInitializationException(msg); }  // 创建过滤器链管理器 FilterChainManager manager = createFilterChainManager();  // 创建基于路径匹配的过滤器链解析器 PathMatchingFilterChainResolver chainResolver = new PathMatchingFilterChainResolver(); chainResolver.setFilterChainManager(manager);  // 返回SpringShiroFilter对象 return new SpringShiroFilter((WebSecurityManager) securityManager, chainResolver);}

从上述源码中可以看到，最终返回了一个SpringShiroFilter对象，即Spring配置文件中的shiroFilter对象，该过滤器拥有三个重要对象：SecurityManager、PathMatchingFilterChainResolver、FilterChainManager。

由于在Spring配置中设置了filterChainDefinitions属性，所以会调用setFilterChainDefinitions方法：

public void setFilterChainDefinitions(String definitions) { Ini ini = new Ini(); ini.load(definitions); //did they explicitly state a 'urls' section? Not necessary, but just in case: Ini.Section section = ini.getSection(IniFilterChainResolverFactory.URLS); if (CollectionUtils.isEmpty(section)) { //no urls section. Since this _is_ a urls chain definition property, just assume the //default section contains only the definitions: section = ini.getSection(Ini.DEFAULT_SECTION_NAME); } /** 获取默认section，也就是加载 /index.jsp = anon /unauthorized.jsp = anon /login.jsp = authc /logout = logout /authenticated.jsp = authc  /** = user 这段配置，从这段配置中可以知道哪种URL需要应用上哪些Filter，像anon、authc、logout就是Filter的名称， Ini.Section实现了Map接口，其key为URL匹配符，value为Filter名称 **/ // 设置filterChainDefinitionMap setFilterChainDefinitionMap(section);}

FilterChainManager用于管理当前Shiro应用的所有Filter，有Shiro默认使用的Filter，也可以是自定义的Filter。下面我们看看FilterChainManager是如何创建出来的：

protected FilterChainManager createFilterChainManager() { // 创建DefaultFilterChainManager DefaultFilterChainManager manager = new DefaultFilterChainManager(); // 创建Shiro默认Filter，根据org.apache.shiro.web.filter.mgt.DefaultFilter创建 Map<String, Filter> defaultFilters = manager.getFilters(); //apply global settings if necessary: for (Filter filter : defaultFilters.values()) { // 设置相关Filter的loginUrl、successUrl、unauthorizedUrl属性 applyGlobalPropertiesIfNecessary(filter); }  // 获取在Spring配置文件中配置的Filter 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); } // 将配置的Filter添加至链中，如果同名Filter已存在则覆盖默认Filter manager.addFilter(name, filter, false); } }  //build up the chains: 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(); // 为配置的每一个URL匹配创建FilterChain定义， // 这样当访问一个URL的时候，一旦该URL配置上则就知道该URL需要应用上哪些Filter // 由于URL配置符会配置多个，所以以第一个匹配上的为准，所以越具体的匹配符应该配置在前面，越宽泛的匹配符配置在后面 manager.createChain(url, chainDefinition); } }  return manager;}

PathMatchingFilterChainResolver对象职责很简单，就是使用ant路径匹配方法匹配访问的URL，由于pathMatchingFilterChainResolver拥有FilterChainManager对象，所以URL匹配上后可以获取该URL需要应用的FilterChain了。

通过上述分析可以知道，Shiro就是通过一系列的URL匹配符配置URL应该应用上的Filter，然后在Filter中完成相应的任务，所以Shiro的所有功能都是通过Filter完成的。当然认证功能也不例外，在上述配置中认证功能是由org.apache.shiro.web.filter.authc.FormAuthenticationFilter完成的。

下面我们就看看入口过滤器SpringShiroFilter的执行流程，是如何执行到FormAuthenticationFilter的。既然是Filter，那么最重要的就是doFilter方法了，由于SpringShiroFilter继承自OncePerRequestFilter，doFilter方法也是在OncePerRequestFilter中定义的：

public final void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws ServletException, IOException { // 用于保证链中同一类型的Filter只会被执行一次 String alreadyFilteredAttributeName = getAlreadyFilteredAttributeName(); if ( request.getAttribute(alreadyFilteredAttributeName) != null ) { log.trace("Filter '{}' already executed. Proceeding without invoking this filter.", getName()); filterChain.doFilter(request, response); } else //noinspection deprecation if (/* added in 1.2: */ !isEnabled(request, response) || /* retain backwards compatibility: */ shouldNotFilter(request) ) { log.debug("Filter '{}' is not enabled for the current request. Proceeding without invoking this filter.", getName()); filterChain.doFilter(request, response); } else { // Do invoke this filter... log.trace("Filter '{}' not yet executed. Executing now.", getName()); request.setAttribute(alreadyFilteredAttributeName, Boolean.TRUE);  try { // 执行真正的功能代码 doFilterInternal(request, response, filterChain); } finally { // Once the request has finished, we're done and we don't // need to mark as 'already filtered' any more. request.removeAttribute(alreadyFilteredAttributeName); } }}

doFilterInternal方法定义AbstractShiroFilter中：

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);  // 创建Subject对象，由此可见，每一个请求到来，都会调用createSubject方法 final Subject subject = createSubject(request, response);  // 通过Subject对象执行过滤器链， subject.execute(new Callable() { public Object call() throws Exception { // 更新会话最后访问时间，用于计算会话超时 updateSessionLastAccessTime(request, response); // 执行过滤器链 executeChain(request, response, chain); return null; } }); } catch (ExecutionException ex) { t = ex.getCause(); } catch (Throwable throwable) { t = throwable; }  // 省略一些代码...}

先看一下，Subject如果是如何创建的：

protected WebSubject createSubject(ServletRequest request, ServletResponse response) { return new WebSubject.Builder(getSecurityManager(), request, response).buildWebSubject();}

跟踪代码最终调用DefaultWebSubjectFactory.createSubject方法：

public Subject createSubject(SubjectContext context) { if (!(context instanceof WebSubjectContext)) { return super.createSubject(context); } WebSubjectContext wsc = (WebSubjectContext) context; SecurityManager securityManager = wsc.resolveSecurityManager(); Session session = wsc.resolveSession(); boolean sessionEnabled = wsc.isSessionCreationEnabled(); PrincipalCollection principals = wsc.resolvePrincipals(); // 判断是已经认证，如果是在没有登录之前，明显返回是false boolean authenticated = wsc.resolveAuthenticated(); String host = wsc.resolveHost(); ServletRequest request = wsc.resolveServletRequest(); ServletResponse response = wsc.resolveServletResponse();  return new WebDelegatingSubject(principals, authenticated, host, session, sessionEnabled, request, response, securityManager);}

接下来看看过滤器链是如何创建与执行的：

protected void executeChain(ServletRequest request, ServletResponse response, FilterChain origChain) throws IOException, ServletException { // 获取当前URL匹配的过滤器链 FilterChain chain = getExecutionChain(request, response, origChain); // 执行过滤器链中的过滤器 chain.doFilter(request, response);} protected FilterChain getExecutionChain(ServletRequest request, ServletResponse response, FilterChain origChain) { FilterChain chain = origChain; // 获取过滤器链解析器，即上面创建的PathMatchingFilterChainResolver对象 FilterChainResolver resolver = getFilterChainResolver(); if (resolver == null) { log.debug("No FilterChainResolver configured. Returning original FilterChain."); return origChain; }  // 调用其getChain方法，根据URL匹配相应的过滤器链 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;}

根据上述Spring配置，假设现在第一次访问URL: "/authenticated.jsp"，则会应用上名为authc的Filter，即FormAuthenticationFilter，根据FormAuthenticationFilter的继承体系，先执行dviceFilter.doFilterInternal方法：

public void doFilterInternal(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException { Exception exception = null;  try { // 执行preHandle boolean continueChain = preHandle(request, response); if (log.isTraceEnabled()) { log.trace("Invoked preHandle method. Continuing chain?: [" + continueChain + "]"); } // 如果preHandle返回false则过滤器链不再执行 if (continueChain) { executeChain(request, response, chain); }  postHandle(request, response); if (log.isTraceEnabled()) { log.trace("Successfully invoked postHandle method"); }  } catch (Exception e) { exception = e; } finally { cleanup(request, response, exception); }}

接下来执行：PathMatchingFilter.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; }  for (String path : this.appliedPaths.keySet()) { // 根据配置，访问URL:"/authenticated.jsp"时，会匹配上FormAuthenticationFilter, // 而FormAuthenticationFilter继承自PathMatchingFilter，所以返回true if (pathsMatch(path, request)) { log.trace("Current requestURI matches pattern '{}'. Determining filter chain execution...", path); Object config = this.appliedPaths.get(path); // 执行isFilterChainContinued方法，该方法调用onPreHandle方法 return isFilterChainContinued(request, response, path, config); } }  //no path matched, allow the request to go through: return true;}

接着执行AccessControlFilter.onPreHandle方法：

public boolean onPreHandle(ServletRequest request, ServletResponse response, Object mappedValue) throws Exception { // 如果isAccessAllowed方法返回false，则会执行onAccessDenied方法 return isAccessAllowed(request, response, mappedValue) || onAccessDenied(request, response, mappedValue);}

接着执行AuthenticatingFilter.isAccessAllowed方法：

@Overrideprotected boolean isAccessAllowed(ServletRequest request, ServletResponse response, Object mappedValue) { return super.isAccessAllowed(request, response, mappedValue) || (!isLoginRequest(request, response) && isPermissive(mappedValue));}super.isAccessAllowed方法，即AuthenticationFilter.isAccessAllowed方法：protected boolean isAccessAllowed(ServletRequest request, ServletResponse response, Object mappedValue) { Subject subject = getSubject(request, response); return subject.isAuthenticated();}

由以上代码可知，由于是第一次访问URL:"/authenticated.jsp"，所以isAccessAllowed方法返回false，所以接着执行FormAuthenticationFilter.onAccessDenied方法：

protected boolean onAccessDenied(ServletRequest request, ServletResponse response) throws Exception { // 第一次访问自然不是登录请求 if (isLoginRequest(request, response)) { // 判断是否是POST请求 if (isLoginSubmission(request, response)) { if (log.isTraceEnabled()) { log.trace("Login submission detected. Attempting to execute login."); } return executeLogin(request, response); } else { if (log.isTraceEnabled()) { log.trace("Login page view."); } //allow them to see the login page ;) return true; } } else { if (log.isTraceEnabled()) { log.trace("Attempting to access a path which requires authentication. Forwarding to the " + "Authentication url [" + getLoginUrl() + "]"); } // 所以执行该方法 saveRequestAndRedirectToLogin(request, response); return false; }} protected void saveRequestAndRedirectToLogin(ServletRequest request, ServletResponse response) throws IOException { // 将request对象保存在session中，以便登录成功后重新转至上次访问的URL saveRequest(request); // 重定向至登录页面，即："/login.jsp" redirectToLogin(request, response);}

根据配置，访问URL:"/login.jsp"时也会应用上FormAuthenticationFilter，由于是重定向所以发起的是GET请求，所以isLoginSubmission()返回false，所以没有执行executeLogin方法，所以能够访问/login.jsp页面。在登录表单中应该设置action=""，这样登录请求会提交至/login.jsp，这时为POST请求，所以会执行executeLogin方法：

protected boolean executeLogin(ServletRequest request, ServletResponse response) throws Exception { // 根据表单填写的用户名密码创建AuthenticationToken AuthenticationToken token = createToken(request, response); if (token == null) { String msg = "createToken method implementation returned null. A valid non-null AuthenticationToken " + "must be created in order to execute a login attempt."; throw new IllegalStateException(msg); } try { // 获取Subject对象 Subject subject = getSubject(request, response); // 执行Subject.login方法进行登录 subject.login(token); // 如果登录成功，重定向至上次访问的URL return onLoginSuccess(token, subject, request, response); } catch (AuthenticationException e) { // 如果登录失败，则设置错误信息至request，并重新返回登录页面 return onLoginFailure(token, e, request, response); }} protected boolean onLoginSuccess(AuthenticationToken token, Subject subject, ServletRequest request, ServletResponse response) throws Exception { // 重定向至上次访问的URL issueSuccessRedirect(request, response); // 由于返回false，所以过滤器链不再执行 return false;} protected boolean onLoginFailure(AuthenticationToken token, AuthenticationException e, ServletRequest request, ServletResponse response) { // 设置错误信息至request setFailureAttribute(request, e); // 由于返回true，所以过滤器链继续执行，所以又返回了登录页面 return true;}

至此，认证流程大致流程就是这样了，限于篇幅，登录的流程具体，请期待下篇博文。

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