Spring Security核心就是一系列的过滤器链，当一个请求来的时候，首先要通过过滤器链的校验，校验通过之后才会访问用户各种信息。
SecurityContextPersistenceFilter
当一个请求来的时候，它会将session中的值传入到该线程中，当请求返回的时候，它会判断该请求线程是否有SecurityContext，如果有它会将其放入到session中，因此保证了请求结果可以在不同的请求之间共享。
UsernamePasswordAuthenticationFilter
用户名密码登陆, 查询数据库, 获取认证.
FilterSecurityInterceptor
当用户登入成功之后，每次发送请求都会使用该filter检查用户是否已经通过了认证(从 security context中查看当前请求用户对应的Authentication 对象是否已经存在)。如果通过了认证，就放行，否则转向登录页面。
主要讲一下UsernamePasswordAuthenticationFilter
首先 UsernamePasswordAuthenticationFilter继承AbstractAuthenticationProcessingFilter
- attemptAuthentication方法被UsernamePasswordAuthenticationFilter重写
- sessionStrategy.onAuthentication() 把认证结果存入session
- successfulAuthentication() 处理认证成功, 发布事件InteractiveAuthenticationSuccessEvent
//AbstractAuthenticationProcessingFilter中
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) res;
if (!requiresAuthentication(request, response)) {
chain.doFilter(request, response);
return;
}
if (logger.isDebugEnabled()) {
logger.debug("Request is to process authentication");
}
Authentication authResult;
try {
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) {
logger.error(
"An internal error occurred while trying to authenticate the user.",
failed);
unsuccessfulAuthentication(request, response, failed);
return;
}
catch (AuthenticationException failed) {
// Authentication failed
unsuccessfulAuthentication(request, response, failed);
return;
}
// Authentication success
if (continueChainBeforeSuccessfulAuthentication) {
chain.doFilter(request, response);
}
successfulAuthentication(request, response, chain, authResult);
}
protected void successfulAuthentication(HttpServletRequest request,
HttpServletResponse response, FilterChain chain, Authentication authResult)
throws IOException, ServletException {
if (logger.isDebugEnabled()) {
logger.debug("Authentication success. Updating SecurityContextHolder to contain: "
+ authResult);
}
SecurityContextHolder.getContext().setAuthentication(authResult);
rememberMeServices.loginSuccess(request, response, authResult);
// Fire event
if (this.eventPublisher != null) {
eventPublisher.publishEvent(new InteractiveAuthenticationSuccessEvent(
authResult, this.getClass()));
}
successHandler.onAuthenticationSuccess(request, response, authResult);
}UsernamePasswordAuthenticationFilter重写 attemptAuthentication方法
//UsernamePasswordAuthenticationFilter中
public Authentication attemptAuthentication(HttpServletRequest request,
HttpServletResponse response) throws AuthenticationException {
if (postOnly && !request.getMethod().equals("POST")) {
throw new AuthenticationServiceException(
"Authentication method not supported: " + request.getMethod());
}
String username = obtainUsername(request);
String password = obtainPassword(request);
if (username == null) {
username = "";
}
if (password == null) {
password = "";
}
username = username.trim();
UsernamePasswordAuthenticationToken authRequest = new UsernamePasswordAuthenticationToken(
username, password);
// Allow subclasses to set the "details" property
setDetails(request, authRequest);
return this.getAuthenticationManager().authenticate(authRequest);
}this.getAuthenticationManager().authenticate(authRequest);
ProviderManager 实现 AuthenticationManager
//在ProviderManager中
public Authentication authenticate(Authentication authentication)
throws AuthenticationException {
Class<? extends Authentication> toTest = authentication.getClass();
AuthenticationException lastException = null;
Authentication result = null;
boolean debug = logger.isDebugEnabled();
for (AuthenticationProvider provider : getProviders()) {
if (!provider.supports(toTest)) {
continue;
}
if (debug) {
logger.debug("Authentication attempt using "
+ provider.getClass().getName());
}
try {
result = provider.authenticate(authentication);
if (result != null) {
copyDetails(authentication, result);
break;
}
}
catch (AccountStatusException e) {
prepareException(e, authentication);
// SEC-546: Avoid polling additional providers if auth failure is due to
// invalid account status
throw e;
}
catch (InternalAuthenticationServiceException e) {
prepareException(e, authentication);
throw e;
}
catch (AuthenticationException e) {
lastException = e;
}
}
。。。。。。。。。。。。。
}result = provider.authenticate(authentication); 传入UsernamePasswordAuthenticationToken获取Authentication
AbstractUserDetailsAuthenticationProvider 实现 AuthenticationProvider，认证用户返回Authentication
//在AbstractUserDetailsAuthenticationProvider中
public Authentication authenticate(Authentication authentication)
throws AuthenticationException {
Assert.isInstanceOf(UsernamePasswordAuthenticationToken.class, authentication,
messages.getMessage(
"AbstractUserDetailsAuthenticationProvider.onlySupports",
"Only UsernamePasswordAuthenticationToken is supported"));
// Determine username
String username = (authentication.getPrincipal() == null) ? "NONE_PROVIDED"
: authentication.getName();
boolean cacheWasUsed = true;
UserDetails user = this.userCache.getUserFromCache(username);
if (user == null) {
cacheWasUsed = false;
try {
user = retrieveUser(username,
(UsernamePasswordAuthenticationToken) authentication);
}
catch (UsernameNotFoundException notFound) {
logger.debug("User '" + username + "' not found");
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 {
preAuthenticationChecks.check(user);
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;
}
}
postAuthenticationChecks.check(user);
if (!cacheWasUsed) {
this.userCache.putUserInCache(user);
}
Object principalToReturn = user;
if (forcePrincipalAsString) {
principalToReturn = user.getUsername();
}
return createSuccessAuthentication(principalToReturn, authentication, user);
}
user = retrieveUser(username,(UsernamePasswordAuthenticationToken) authentication); 获取用户信息。
DaoAuthenticationProvider 继承 AbstractUserDetailsAuthenticationProvider调用 获取用户信息接口
//在DaoAuthenticationProvider中
protected final UserDetails retrieveUser(String username,
UsernamePasswordAuthenticationToken authentication)
throws AuthenticationException {
UserDetails loadedUser;
try {
loadedUser = this.getUserDetailsService().loadUserByUsername(username);
}
catch (UsernameNotFoundException notFound) {
if (authentication.getCredentials() != null) {
String presentedPassword = authentication.getCredentials().toString();
passwordEncoder.isPasswordValid(userNotFoundEncodedPassword,
presentedPassword, null);
}
throw notFound;
}
catch (Exception repositoryProblem) {
throw new InternalAuthenticationServiceException(
repositoryProblem.getMessage(), repositoryProblem);
}
if (loadedUser == null) {
throw new InternalAuthenticationServiceException(
"UserDetailsService returned null, which is an interface contract violation");
}
return loadedUser;
}loadedUser = this.getUserDetailsService().loadUserByUsername(username); 调用我们自定义的获取用户的实现。
总结：模版模式：AbstractAuthenticationProcessingFilter定义了抽象方法attemptAuthentication（）供子类实现。