Spring-security核心拦截器

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(一) ExceptionTranslationFilter

Spring-security的异常拦截器：这个拦截器只拦截AuthenticationException和AccessDeniedException异常，其他异常直接抛出

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
            throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;
        try {
            chain.doFilter(request, response);
            logger.debug("Chain processed normally");
        }
        catch (IOException ex) {
			若捕获IOException直接抛出
            throw ex;
        }
        catch (Exception ex) {
            // Try to extract a SpringSecurityException from the stacktrace
            Throwable[] causeChain = throwableAnalyzer.determineCauseChain(ex);
			//获取认证异常
            RuntimeException ase = (AuthenticationException) throwableAnalyzer.getFirstThrowableOfType(AuthenticationException.class, causeChain);
            if (ase == null) {
			//若没有找到认证异常，就找授权异常
                ase = (AccessDeniedException)throwableAnalyzer.getFirstThrowableOfType(AccessDeniedException.class, causeChain);
            }
            if (ase != null) {
				//处理spring-security抛出的异常
				//1. 若是认证异常交给AuthenticationEntryPoint处理
				//2. 若是授权异常交给AccessDeniedHandler处理
                handleSpringSecurityException(request, response, chain, ase);
            } else {
                //省略… 抛出其他异常
            }
        }
    }

 

AuthenticationEntryPoint

 

当用户请求了一个受保护的资源，但是用户没有通过认证，那么抛出异常，AuthenticationEntryPoint. Commence(..)就会调用

public interface AuthenticationEntryPoint {
    void commence(HttpServletRequest request, HttpServletResponse response, AuthenticationException authException)
        throws IOException, ServletException;
}

 LoginUrlAuthenticationEntryPoint ：跳转到登录页面

  

SavedRequest & RequestCache

 在用户还为通过认证，访问了需要认证的资源，那么spring-security会保存当前的request，然后跳转到登录界面进行认证，在认证通过后，spring-security会跳转到保存的request；这个功能就是通过SavedRequest 和RequestCache 接口

 

 1. SavedRequest：保存request的所有信息，默认的实现是DefaultSavedRequest

public interface SavedRequest extends java.io.Serializable {
    String getRedirectUrl();
    List getCookies();
    String getMethod();
    List getHeaderValues(String name);
    Collection getHeaderNames();
    List getLocales();
    String[] getParameterValues(String name);
    Map getParameterMap();
}

 

 

 2. RequestCache：默认的实现HttpSessionRequestCache，保存SavedRequest到session，

可以自己设置RequestMatcher，默认是AnyRequestMatcher

public interface RequestCache {
    void saveRequest(HttpServletRequest request, HttpServletResponse response);
    SavedRequest getRequest(HttpServletRequest request, HttpServletResponse response);
    HttpServletRequest getMatchingRequest(HttpServletRequest request, HttpServletResponse response);
    void removeRequest(HttpServletRequest request, HttpServletResponse response);
} 

 

AccessDeniedHandler

 用户已经通过了认证，在访问一个受保护的资源，但是权限不够，那么抛出异常，AccessDeniedHandler. Handle(..)会调用

AccessDeniedHandlerImpl：若用户配置了权限不足的错误页面，那么就会跳转到错误页面；

若没有配置，那么就返回一个403

 

(二) SecurityContextPersistenceFilter

 

这个拦截器只完成两个任务：

1. 通过SecurityContextRepository获取到SecurityContext，默认是从session中获取，若没有找到，那么SecurityContextRepository就是创建一个空的，然后在通过SecurityContextHolder把获取到的SecurityContext保存到ThreadLocal

2. 在请求结束后通过SecurityContextHolder清除掉ThreadLocal中的SecurityContext

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
            throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;
确保这个拦截器一次请求只执行一次
        if (request.getAttribute(FILTER_APPLIED) != null) {
            chain.doFilter(request, response);
            return;
        }
       	//省略…..
        HttpRequestResponseHolder holder = new HttpRequestResponseHolder(request, response);
		通过SecurityContextRepository获取SecurityContext，SecurityContextRepository默认是HttpSessionSecurityContextRepository
        SecurityContext contextBeforeChainExecution = repo.loadContext(holder);
        try {
			默认SecurityContextHolder把SecurityContext保存到ThreadLocal中
            SecurityContextHolder.setContext(contextBeforeChainExecution);
            chain.doFilter(holder.getRequest(), holder.getResponse());
        } finally {
            SecurityContext contextAfterChainExecution = SecurityContextHolder.getContext();
            // Crucial removal of SecurityContextHolder contents - do this before anything else.
            清除SecurityContext,保存SecurityContext到session中
SecurityContextHolder.clearContext();
            repo.saveContext(contextAfterChainExecution, holder.getRequest(), holder.getResponse());
            request.removeAttribute(FILTER_APPLIED); 
            }
        }
    }

(三)  UsernamePasswordAuthenticationFilter

 处理用户登录的拦截器，继承与AbstractAuthenticationProcessingFilter。

在AbstractAuthenticationProcessingFilter中的doFilter:

 

public void doFilter(ServletRequest req,ServletResponse res, FilterChain chain)  throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;
        //匹配url，通过RequestMatcher判断是否认证请求的url是指定结尾的，默认的结尾是/j_spring_security_check，所有在form表单提交的地址要以/j_spring_security_check结尾
        if (!requiresAuthentication(request, response)) {
            chain.doFilter(request, response);
            return;
        }
        Authentication authResult;
        try {
            //调用子类UsernamePasswordAuthenticationFilter的attemptAuthentication方法
            authResult = attemptAuthentication(request, response);
            if (authResult == null) {
                // return immediately as subclass has indicated that it hasn't completed authentication
                return;
            }
            sessionStrategy.onAuthentication(authResult, request, response);
        } catch(InternalAuthenticationServiceException failed) {
            // 在认证的过程中抛出了异常，那么就认证失败。
	    //从SecurityContextHolder清除掉SecurityContext；
	    //AuthenticationFailureHandler处理后续操作，跳转到认证失败URL可以在security.xml中配置
	    //RememberMeServices  删除保存的cookie
            unsuccessfulAuthentication(request, response, failed);
            return;
        }
        catch (AuthenticationException failed) {
            // Authentication failed
            unsuccessfulAuthentication(request, response, failed);
            return;
        }
        // Authentication success 
	//保存SecurityContext
	//RememberMeServices保存cookie
	//AuthenticationSuccessHandler 若有缓存到session中的URL，那么跳转，若没有，那么跳转到默认的URL，可以在security.xml中配置
        successfulAuthentication(request, response, chain, authResult);
    }

 

 UsernamePasswordAuthenticationFilter中的attemptAuthentication方法：

public Authentication attemptAuthentication(HttpServletRequest request, HttpServletResponse response) throws AuthenticationException {
	//判断是否是POST请求，默认是要求必须是POST
        if (postOnly && !request.getMethod().equals("POST")) {
            throw new AuthenticationServiceException("Authentication method not supported: " + request.getMethod());
        }
        //从request中解析出表单提交的username  password，默认的参数名称是：j_username j_password 
        String username = obtainUsername(request);
        String password = obtainPassword(request);
        //省略……
        UsernamePasswordAuthenticationToken authRequest = new UsernamePasswordAuthenticationToken(username, password);
        // Allow subclasses to set the "details" property
        setDetails(request, authRequest);

        //获取到AuthenticationManager调用authenticate方法进行认证
        return this.getAuthenticationManager().authenticate(authRequest);
    }