2019独角兽企业重金招聘Python工程师标准>>>

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 authenticationreturn;}//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 successif (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);}

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UsernamePasswordAuthenticationTokenUsernamePasswordAuthenticationToken authRequest = new UsernamePasswordAuthenticationToken(username, password);// Place the last username attempted into HttpSession for viewsHttpSession 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);}

这里的authenticationManager变量也是通过解析form-login标签，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 filterformFilterId = pc.getReaderContext().generateBeanName(formFilter);pc.registerBeanComponent(new BeanComponentDefinition(formFilter, formFilterId));injectRememberMeServicesRef(formFilter, rememberMeServicesId);}}

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detailscopyDetails(authentication, result);break;}} catch (AccountStatusException e) {// SEC-546: Avoid polling additional providers if auth failure is due to invalid account statuseventPublisher.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。

现在来看DaoAuthenticationProvider的认证处理，实际上authenticate由父类AbstractUserDetailsAuthenticationProvider完成。代码如下

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UserDetailsuser = 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Authenticationreturn createSuccessAuthentication(principalToReturn, authentication, user);}

继续看DaoAuthenticationProvider的retrieveUser方法

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//属性user-service-refloadedUser = 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;}

实际上，只要实现UserDetailsService接口的loadUserByUsername方法，就完成了登录认证的工作

<authentication-manager alias="authenticationManager"><authentication-provider user-service-ref="userDetailsManager"/>
</authentication-manager>

很多教程上说配置JdbcUserDetailsManager这个UserDetailsService，实际上该类的父类
JdbcDaoImpl方法loadUserByUsername代码如下：

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Groupif (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Userreturn new User(returnUsername, userFromUserQuery.getPassword(), userFromUserQuery.isEnabled(),true, true, true, combinedAuthorities);}

其他的provider，如
RememberMeAuthenticationProvider、AnonymousAuthenticationProvider的认证处理都很简单，首先判断是否支持Authentication，不支持直接返回null，支持也不处理直接返回该Authentication

这里需要强调一下，DaoAuthenticationProvider只支持UsernamePasswordAuthenticationToken这个Authentication。如果对其他的Authentication，DaoAuthenticationProvider是不做处理的