Sring Security3登录权限认证解析

1、UsernamePasswordAuthenticationFilter过滤器对应的类路径为 
org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter 
实际上这个Filter类的doFilter是父类AbstractAuthenticationProcessingFilter的     

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)

            throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;
        //判断form-login标签是否包含login-processing-url属性
          //如果没有采用默认的url：j_spring_security_check
        //如果拦截的url不需要认证，直接跳过
        if (!requiresAuthentication(request, response)) {
            chain.doFilter(request, response);


            return;
        }

        if (logger.isDebugEnabled()) {
            logger.debug("Request is to process authentication");
        }

        Authentication authResult;

        try {
            //由子类完成认证
            authResult = attemptAuthentication(request, response);
            if (authResult == null) {
                // return immediately as subclass has indicated that it hasn't completed authentication
                return;
            }
            //session策略处理认证信息
              //sessionStrategy是通过session-management标签中定义的
              //session管理策略构造的SessionAuthenticationStrategy
            //具体的session管理比较复杂，部分后面单个篇幅讲解
            sessionStrategy.onAuthentication(authResult, request, response);
        }
        catch (AuthenticationException failed) {
            // Authentication failed
            //认证失败处理
            unsuccessfulAuthentication(request, response, failed);

            return;
        }

        // Authentication success
        if (continueChainBeforeSuccessfulAuthentication) {
            chain.doFilter(request, response);
        }
        //认证成功处理
         //1.向SecurityContext中设置Authentication认证信息
         //2.如果有remember me服务，则查找请求参数中是否包含_spring_security_remember_me，如果该参数值为true、yes、on、1则执行remember me功能:添加cookie、入库。为下次请求时自动登录做准备
         //3.发布认证成功事件
         //4.执行跳转
        successfulAuthentication(request, response, authResult);

    }

2、子类UsernamePasswordAuthenticationFilter的认证方法attemptAuthentication

       public Authentication attemptAuthentication(HttpServletRequest request, HttpServletResponse response) throws AuthenticationException {
        //只处理post提交的请求
        if (postOnly && !request.getMethod().equals("POST")) {
            throw new AuthenticationServiceException("Authentication method not supported: " + request.getMethod());
        }
        //获取用户名、密码数据
        String username = obtainUsername(request);
        String password = obtainPassword(request);

        if (username == null) {
            username = "";
        }
        if (password == null) {
            password = "";
        }
        username = username.trim();
        //构造未认证的UsernamePasswordAuthenticationToken
        UsernamePasswordAuthenticationToken authRequest = new UsernamePasswordAuthenticationToken(username, password);

        // Place the last username attempted into HttpSession for views
        HttpSession session = request.getSession(false);
        //如果session不为空，添加username到session中
        if (session != null || getAllowSessionCreation()) {
            request.getSession().setAttribute(SPRING_SECURITY_LAST_USERNAME_KEY, TextEscapeUtils.escapeEntities(username));
        }


        // Allow subclasses to set the "details" property
        //设置details，这里就是设置org.springframework.security.web.
        //authentication.WebAuthenticationDetails实例到details中
        setDetails(request, authRequest);
        //通过AuthenticationManager:ProviderManager完成认证任务
        return this.getAuthenticationManager().authenticate(authRequest);
    }

3、这里的authenticationManager变量也是通过解析form-login标签，Spring安全配置文件为applicationContext-security.xml，构造bean时注入的，具体解析类为：org.springframework.security.config.http.AuthenticationConfigBuilder 
代码片段为：

    void createFormLoginFilter(BeanReference sessionStrategy, BeanReference authManager) {
        Element formLoginElt = DomUtils.getChildElementByTagName(httpElt, Elements.FORM_LOGIN);
        if (formLoginElt != null || autoConfig) {
            FormLoginBeanDefinitionParser parser = new FormLoginBeanDefinitionParser("/j_spring_security_check",
                    AUTHENTICATION_PROCESSING_FILTER_CLASS, requestCache, sessionStrategy);
            parser.parse(formLoginElt, pc);
            formFilter = parser.getFilterBean();
            formEntryPoint = parser.getEntryPointBean();
        }
        if (formFilter != null) {
            formFilter.getPropertyValues().addPropertyValue("allowSessionCreation", new Boolean(allowSessionCreation));
            //设置authenticationManager的bean依赖
            formFilter.getPropertyValues().addPropertyValue("authenticationManager", authManager);

            // Id is required by login page filter
            formFilterId = pc.getReaderContext().generateBeanName(formFilter);
            pc.registerBeanComponent(new BeanComponentDefinition(formFilter, formFilterId));
            injectRememberMeServicesRef(formFilter, rememberMeServicesId);
        }
    }

4、继续看ProviderManager代码。实际上authenticate方法由ProviderManager的父类定义，并且authenticate方法内调用子类的doAuthentication方法，记得这是设计模式中的模板模式

    public Authentication doAuthentication(Authentication authentication) throws AuthenticationException {
        Class<? extends Authentication> toTest = authentication.getClass();
        AuthenticationException lastException = null;
        Authentication result = null;
        //循环ProviderManager中的providers，由具体的provider执行认证操作
        for (AuthenticationProvider provider : getProviders()) {
        System.out.println("AuthenticationProvider: " + provider.getClass().getName());
            if (!provider.supports(toTest)) {
                continue;
            }
            logger.debug("Authentication attempt using " + provider.getClass().getName());
            try {
                result = provider.authenticate(authentication);
                if (result != null) {
                    //复制details
                    copyDetails(authentication, result);
                    break;
                }
            } catch (AccountStatusException e) {
                // SEC-546: Avoid polling additional providers if auth failure is due to invalid account status
                eventPublisher.publishAuthenticationFailure(e, authentication);
                throw e;
            } catch (AuthenticationException e) {
                lastException = e;
            }
        }
        if (result == null && parent != null) {
            // Allow the parent to try.
            try {
                result = parent.authenticate(authentication);
            } catch (ProviderNotFoundException e) {
                // ignore as we will throw below if no other exception occurred prior to calling parent and the parent
                // may throw ProviderNotFound even though a provider in the child already handled the request
            } catch (AuthenticationException e) {
                lastException = e;
            }
        }
        if (result != null) {
            eventPublisher.publishAuthenticationSuccess(result);
            return result;
        }

        // Parent was null, or didn't authenticate (or throw an exception).
        if (lastException == null) {
            lastException = new ProviderNotFoundException(messages.getMessage("ProviderManager.providerNotFound",
                        new Object[] {toTest.getName()}, "No AuthenticationProvider found for {0}"));
        }
        //由注入进来的org.springframework.security.authentication.DefaultAuthenticationEventPublisher完成事件发布任务
        eventPublisher.publishAuthenticationFailure(lastException, authentication);
        throw lastException;
    }

ProviderManager类中的providers由哪些provider呢？如果看完authentication-manager标签解析的讲解，应该知道注入到providers中的provider分别为： 
org.springframework.security.authentication.dao.DaoAuthenticationProvider 
org.springframework.security.authentication.AnonymousAuthenticationProvider 
其他的provider根据特殊情况，再添加到providers中的，如remember me功能的provider 
org.springframework.security.authentication.RememberMeAuthenticationProvider 
可以看出来，ProviderManager仅仅是管理provider的，具体的authenticate认证任务由各自provider来完成。

5、现在来看DaoAuthenticationProvider的认证处理，实际上authenticate由父类AbstractUserDetailsAuthenticationProvider完成：

   public Authentication authenticate(Authentication authentication) throws AuthenticationException {
        …………
         //获取登录的用户名
        String username = (authentication.getPrincipal() == null) ? "NONE_PROVIDED" : authentication.getName();
        boolean cacheWasUsed = true;
        //如果配置了缓存，从缓存中获取UserDetails实例
        UserDetails user = this.userCache.getUserFromCache(username);
        if (user == null) {
            cacheWasUsed = false;
            try {
                //如果UserDetails为空，则由具体子类DaoAuthenticationProvider
                //根据用户名、authentication获取UserDetails
                user = retrieveUser(username, (UsernamePasswordAuthenticationToken) authentication);
            } catch (UsernameNotFoundException notFound) {
                if (hideUserNotFoundExceptions) {
                    throw new BadCredentialsException(messages.getMessage(
                            "AbstractUserDetailsAuthenticationProvider.badCredentials", "Bad credentials"));
                } else {
                    throw notFound;
                }
            }
            Assert.notNull(user, "retrieveUser returned null - a violation of the interface contract");
        }

        try {
            //一些认证检查（账号是否可用、是否过期、是否被锁定）
            preAuthenticationChecks.check(user);
            //额外的密码检查（salt、passwordEncoder）
            additionalAuthenticationChecks(user, (UsernamePasswordAuthenticationToken) authentication);
        } catch (AuthenticationException exception) {
            if (cacheWasUsed) {
                // There was a problem, so try again after checking
                // we're using latest data (i.e. not from the cache)
                cacheWasUsed = false;
                user = retrieveUser(username, (UsernamePasswordAuthenticationToken) authentication);
                preAuthenticationChecks.check(user);
                additionalAuthenticationChecks(user, (UsernamePasswordAuthenticationToken) authentication);
            } else {
                throw exception;
            }
        }
        //检查账号是否过期
        postAuthenticationChecks.check(user);
        //添加UserDetails到缓存中
        if (!cacheWasUsed) {
            this.userCache.putUserInCache(user);
        }
        Object principalToReturn = user;
        if (forcePrincipalAsString) {
            principalToReturn = user.getUsername();
        }
        //返回成功认证后的Authentication
        return createSuccessAuthentication(principalToReturn, authentication, user);
    }

6、之前看代码，我首先看到的就是父类AbstractUserDetailsAuthenticationProvider，因为根据我们自己的代码顺藤摸瓜，首先找到的是父类，走到retrieveUser方法时，不知道是哪个子类来实现它的，最后在网上看到是DaoAuthenticationProvider进行了实现，这个方法的作用就是如果缓存中没有用户信息，通过数据库查询方法，检索用户信息。

    protected final UserDetails retrieveUser(String username, UsernamePasswordAuthenticationToken authentication)
            throws AuthenticationException {
        UserDetails loadedUser;
        try {
            //最关键的部分登场了
              //UserDetailService就是authentication-provider标签中定义的

            //<authentication-manager alias="xxxAuthenticationManager">
            //    <authentication-provider user-service-ref="xxxUserDetailService">
            //     <password-encoder ref="boPasswordEncoder" />
            //    </authentication-provider>
            //</authentication-manager>
            //属性user-service-ref可以用来定义UserDetailsService的接口实现类，来实现loadUserByUsername方法。

            loadedUser = this.getUserDetailsService().loadUserByUsername(username);
        }
        catch (DataAccessException repositoryProblem) {
            throw new AuthenticationServiceException(repositoryProblem.getMessage(), repositoryProblem);
        }


        if (loadedUser == null) {
            throw new AuthenticationServiceException(
                    "UserDetailsService returned null, which is an interface contract violation");
        }
        return loadedUser;
    }

7、UserDetailsService的接口实现类，来实现loadUserByUsername方法：

    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException, DataAccessException {
        //根据username从数据库中查询User数据
        List<UserDetails> users = loadUsersByUsername(username);

        if (users.size() == 0) {
            throw new UsernameNotFoundException(
                    messages.getMessage("JdbcDaoImpl.notFound", new Object[]{username}, "Username {0} not found"), username);
        }

        UserDetails user = users.get(0); // contains no GrantedAuthority[]
        Set<GrantedAuthority> dbAuthsSet = new HashSet<GrantedAuthority>();
        //添加授权信息
        if (enableAuthorities) {
            dbAuthsSet.addAll(loadUserAuthorities(user.getUsername()));
        }
        //是否使用了Group
        if (enableGroups) {
            dbAuthsSet.addAll(loadGroupAuthorities(user.getUsername()));
        }
        List<GrantedAuthority> dbAuths = new ArrayList<GrantedAuthority>(dbAuthsSet);
        addCustomAuthorities(user.getUsername(), dbAuths);
        if (dbAuths.size() == 0) {
            throw new UsernameNotFoundException(
                    messages.getMessage("JdbcDaoImpl.noAuthority",
                            new Object[] {username}, "User {0} has no GrantedAuthority"), username);
        }
        return createUserDetails(username, user, dbAuths);
    }

    //usersByUsernameQuery查询语句可配置
     //直接从数据库中查询该username对应的数据，并构造User对象
    protected List<UserDetails> loadUsersByUsername(String username) {
        return getJdbcTemplate().query(usersByUsernameQuery, new String[] {username}, new RowMapper<UserDetails>() {
            public UserDetails mapRow(ResultSet rs, int rowNum) throws SQLException {
                String username = rs.getString(1);
                String password = rs.getString(2);
                boolean enabled = rs.getBoolean(3);
                return new User(username, password, enabled, true, true, true, AuthorityUtils.NO_AUTHORITIES);
            }


        });
    }

……
    protected UserDetails createUserDetails(String username, UserDetails userFromUserQuery,
            List<GrantedAuthority> combinedAuthorities) {
        String returnUsername = userFromUserQuery.getUsername();


        if (!usernameBasedPrimaryKey) {
            returnUsername = username;
        }
        //根据用户名、密码、enabled、授权列表构造UserDetails实例User
        return new User(returnUsername, userFromUserQuery.getPassword(), userFromUserQuery.isEnabled(),
                true, true, true, combinedAuthorities);
    }

实现UserDetailsService接口的loadUserByUsername方法，就完成了登录认证的工作。