Spring Security4.1.3实现拦截登录后向登录页面跳转方式(redirect或forward)返回被拦截界面

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一、看下内部原理

简化后的认证过程分为7步:

  1. 用户访问网站,打开了一个链接(origin url)。

  2. 请求发送给服务器,服务器判断用户请求了受保护的资源。

  3. 由于用户没有登录,服务器重定向到登录页面

  4. 填写表单,点击登录

  5. 浏览器将用户名密码以表单形式发送给服务器

  6. 服务器验证用户名密码。成功,进入到下一步。否则要求用户重新认证(第三步)

  7. 服务器对用户拥有的权限(角色)判定: 有权限,重定向到origin url; 权限不足,返回状态码403("forbidden").

从第3步,我们可以知道,用户的请求被中断了。

用户登录成功后(第7步),会被重定向到origin url,spring security通过使用缓存的request,使得被中断的请求能够继续执行。


使用缓存

用户登录成功后,页面重定向到origin url。浏览器发出的请求优先被拦截器RequestCacheAwareFilter拦截,RequestCacheAwareFilter通过其持有的RequestCache对象实现request的恢复。

public void doFilter(ServletRequest request, ServletResponse response,            FilterChain chain) throws IOException, ServletException {                // request匹配,则取出,该操作同时会将缓存的request从session中删除        HttpServletRequest wrappedSavedRequest = requestCache.getMatchingRequest(                (HttpServletRequest) request, (HttpServletResponse) response);                // 优先使用缓存的request        chain.doFilter(wrappedSavedRequest == null ? request : wrappedSavedRequest,                response);    }


何时缓存

首先,我们需要了解下RequestCache以及ExceptionTranslationFilter。

RequestCache

RequestCache接口声明了缓存与恢复操作。默认实现类是HttpSessionRequestCache。HttpSessionRequestCache的实现比较简单,这里只列出接口的声明:

public interface RequestCache {    // 将request缓存到session中    void saveRequest(HttpServletRequest request, HttpServletResponse response);        // 从session中取request    SavedRequest getRequest(HttpServletRequest request, HttpServletResponse response);        // 获得与当前request匹配的缓存,并将匹配的request从session中删除    HttpServletRequest getMatchingRequest(HttpServletRequest request,            HttpServletResponse response);        // 删除缓存的request    void removeRequest(HttpServletRequest request, HttpServletResponse response);}

ExceptionTranslationFilter

ExceptionTranslationFilter 是Spring Security的核心filter之一,用来处理AuthenticationException和AccessDeniedException两种异常。

在我们的例子中,AuthenticationException指的是未登录状态下访问受保护资源,AccessDeniedException指的是登陆了但是由于权限不足(比如普通用户访问管理员界面)。

ExceptionTranslationFilter 持有两个处理类,分别是AuthenticationEntryPoint和AccessDeniedHandler。

ExceptionTranslationFilter 对异常的处理是通过这两个处理类实现的,处理规则很简单:

规则1. 如果异常是 AuthenticationException,使用 AuthenticationEntryPoint 处理规则2. 如果异常是 AccessDeniedException 且用户是匿名用户,使用 AuthenticationEntryPoint 处理规则3. 如果异常是 AccessDeniedException 且用户不是匿名用户,如果否则交给 AccessDeniedHandler 处理。


对应以下代码

private void handleSpringSecurityException(HttpServletRequest request,            HttpServletResponse response, FilterChain chain, RuntimeException exception)            throws IOException, ServletException {        if (exception instanceof AuthenticationException) {            logger.debug(                    "Authentication exception occurred; redirecting to authentication entry point",                    exception);            sendStartAuthentication(request, response, chain,                    (AuthenticationException) exception);        }        else if (exception instanceof AccessDeniedException) {            if (authenticationTrustResolver.isAnonymous(SecurityContextHolder                    .getContext().getAuthentication())) {                logger.debug(                        "Access is denied (user is anonymous); redirecting to authentication entry point",                        exception);                sendStartAuthentication(                        request,                        response,                        chain,                        new InsufficientAuthenticationException(                                "Full authentication is required to access this resource"));            }            else {                logger.debug(                        "Access is denied (user is not anonymous); delegating to AccessDeniedHandler",                        exception);                accessDeniedHandler.handle(request, response,                        (AccessDeniedException) exception);            }        }    }


AccessDeniedHandler 默认实现是 AccessDeniedHandlerImpl。该类对异常的处理是返回403错误码。

public void handle(HttpServletRequest request, HttpServletResponse response,            AccessDeniedException accessDeniedException) throws IOException,            ServletException {    if (!response.isCommitted()) {        if (errorPage != null) {  // 定义了errorPage            // errorPage中可以操作该异常            request.setAttribute(WebAttributes.ACCESS_DENIED_403,                    accessDeniedException);            // 设置403状态码            response.setStatus(HttpServletResponse.SC_FORBIDDEN);            // 转发到errorPage            RequestDispatcher dispatcher = request.getRequestDispatcher(errorPage);            dispatcher.forward(request, response);        }        else { // 没有定义errorPage,则返回403状态码(Forbidden),以及错误信息            response.sendError(HttpServletResponse.SC_FORBIDDEN,                    accessDeniedException.getMessage());        }    }}


AuthenticationEntryPoint 默认实现是 LoginUrlAuthenticationEntryPoint, 该类的处理是转发或重定向到登录页面

public void commence(HttpServletRequest request, HttpServletResponse response,            AuthenticationException authException) throws IOException, ServletException {    String redirectUrl = null;    if (useForward) {        if (forceHttps && "http".equals(request.getScheme())) {            // First redirect the current request to HTTPS.            // When that request is received, the forward to the login page will be            // used.            redirectUrl = buildHttpsRedirectUrlForRequest(request);        }        if (redirectUrl == null) {            String loginForm = determineUrlToUseForThisRequest(request, response,                    authException);            if (logger.isDebugEnabled()) {                logger.debug("Server side forward to: " + loginForm);            }            RequestDispatcher dispatcher = request.getRequestDispatcher(loginForm);                // 转发            dispatcher.forward(request, response);            return;        }    }    else {        // redirect to login page. Use https if forceHttps true        redirectUrl = buildRedirectUrlToLoginPage(request, response, authException);    }        // 重定向    redirectStrategy.sendRedirect(request, response, redirectUrl);}

了解完这些,回到我们的例子。

第3步时,用户未登录的情况下访问受保护资源,ExceptionTranslationFilter会捕获到AuthenticationException异常(规则1)。页面需要跳转,ExceptionTranslationFilter在跳转前使用requestCache缓存request。

protected void sendStartAuthentication(HttpServletRequest request,            HttpServletResponse response, FilterChain chain,            AuthenticationException reason) throws ServletException, IOException {    // SEC-112: Clear the SecurityContextHolder's Authentication, as the    // existing Authentication is no longer considered valid    SecurityContextHolder.getContext().setAuthentication(null);    // 缓存 request    requestCache.saveRequest(request, response);    logger.debug("Calling Authentication entry point.");    authenticationEntryPoint.commence(request, response, reason);}


二、了解了以上原理以及上篇的forward和redirect的区别,配置实现如下,基于springsecurity4.1.3版本

配置文件:完整的

<?xml version="1.0" encoding="UTF-8"?><beans:beans xmlns="http://www.springframework.org/schema/security"xmlns:beans="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/securityhttp://www.springframework.org/schema/security/spring-security.xsd"><http auto-config="true" use-expressions="true" entry-point-ref="myLoginUrlAuthenticationEntryPoint"><form-login login-page="/login"            authentication-failure-url="/login?error"             login-processing-url="/login"            authentication-success-handler-ref="myAuthenticationSuccessHandler" />            <!-- 认证成功用自定义类myAuthenticationSuccessHandler处理 -->                  <logout logout-url="/logout" logout-success-url="/" invalidate-session="true"delete-cookies="JSESSIONID"/><csrf disabled="true" /><intercept-url pattern="/order/*" access="hasRole('ROLE_USER')"/></http><!-- 使用自定义类myUserDetailsService从数据库获取用户信息 --><authentication-manager>          <authentication-provider user-service-ref="myUserDetailsService">          <!-- 加密 -->            <password-encoder hash="md5">            </password-encoder>        </authentication-provider>    </authentication-manager>        <!-- 被认证请求向登录界面跳转采用forward方式 -->    <beans:bean id="myLoginUrlAuthenticationEntryPoint"     class="org.springframework.security.web.authentication.LoginUrlAuthenticationEntryPoint">    <beans:constructor-arg name="loginFormUrl" value="/login"></beans:constructor-arg>    <beans:property name="useForward" value="true"/>    </beans:bean></beans:beans>


主要配置

<http auto-config="true" use-expressions="true" entry-point-ref="myLoginUrlAuthenticationEntryPoint"> <!-- 被认证请求向登录界面跳转采用forward方式 -->    <beans:bean id="myLoginUrlAuthenticationEntryPoint"     class="org.springframework.security.web.authentication.LoginUrlAuthenticationEntryPoint">    <beans:constructor-arg name="loginFormUrl" value="/login"></beans:constructor-arg>    <beans:property name="useForward" value="true"/>    </beans:bean>

从上面的分析可知,默认情况下采用的是redirect方式,这里通过配置从而实现了forward方式,这里还是直接利用的security自带的类LoginUrlAuthenticationEntryPoint,只不过进行了以上配置:

/** * Performs the redirect (or forward) to the login form URL. */public void commence(HttpServletRequest request, HttpServletResponse response,AuthenticationException authException) throws IOException, ServletException {String redirectUrl = null;if (useForward) {if (forceHttps && "http".equals(request.getScheme())) {// First redirect the current request to HTTPS.// When that request is received, the forward to the login page will be// used.redirectUrl = buildHttpsRedirectUrlForRequest(request);}if (redirectUrl == null) {String loginForm = determineUrlToUseForThisRequest(request, response,authException);if (logger.isDebugEnabled()) {logger.debug("Server side forward to: " + loginForm);}RequestDispatcher dispatcher = request.getRequestDispatcher(loginForm);dispatcher.forward(request, response);return;}}else {// redirect to login page. Use https if forceHttps trueredirectUrl = buildRedirectUrlToLoginPage(request, response, authException);}redirectStrategy.sendRedirect(request, response, redirectUrl);}

登录成功后的类配置,存入登录user信息后交给认证成功后的处理类MyAuthenticationSuccessHandler,该类集成了SavedRequestAwareAuthenticationSuccessHandler,他会从缓存中提取请求,从而可以恢复之前请求的数据

/** * 登录后操作 *  * @author HHL * @date *  */@Componentpublic class MyAuthenticationSuccessHandler extendsSavedRequestAwareAuthenticationSuccessHandler {@Autowiredprivate IUserService userService;@Overridepublic void onAuthenticationSuccess(HttpServletRequest request,HttpServletResponse response, Authentication authentication)throws IOException, ServletException {// 认证成功后,获取用户信息并添加到session中UserDetails userDetails = (UserDetails) authentication.getPrincipal();MangoUser user = userService.getUserByName(userDetails.getUsername());request.getSession().setAttribute("user", user);super.onAuthenticationSuccess(request, response, authentication);}}

SavedRequestAwareAuthenticationSuccessHandler中的onAuthenticationSuccess方法;

@Overridepublic void onAuthenticationSuccess(HttpServletRequest request,HttpServletResponse response, Authentication authentication)throws ServletException, IOException {SavedRequest savedRequest = requestCache.getRequest(request, response);if (savedRequest == null) {super.onAuthenticationSuccess(request, response, authentication);return;}String targetUrlParameter = getTargetUrlParameter();if (isAlwaysUseDefaultTargetUrl()|| (targetUrlParameter != null && StringUtils.hasText(request.getParameter(targetUrlParameter)))) {requestCache.removeRequest(request, response);super.onAuthenticationSuccess(request, response, authentication);return;}clearAuthenticationAttributes(request);// Use the DefaultSavedRequest URLString targetUrl = savedRequest.getRedirectUrl();logger.debug("Redirecting to DefaultSavedRequest Url: " + targetUrl);getRedirectStrategy().sendRedirect(request, response, targetUrl);}
4.1.3中如果默认不配置的话也是采用的SavedRequestAwareAuthenticationSuccessHandler进行处理,详情可参见:Spring实战篇系列----源码解析Spring Security中的过滤器Filter初始化


上述实现了跳转到登录界面采用forward方式,就是浏览器地址栏没有变化,当然也可采用redirect方式,地址栏变为登录界面地址栏,当登录完成后恢复到原先的请求页面,请求信息会从requestCache中还原回来。可参考 Spring实战篇系列----spring security4.1.3配置以及踩过的坑



参考:

https://segmentfault.com/a/1190000004183264

http://gtbald.iteye.com/blog/1214132







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