SpringSecurity6从入门到实战之登录表单的提交(源码级讲解,耐心看完)

文接上回,当SpringSecurity帮我们生成了一个默认对象.本文继续对登录流程进行探索,我们如何通过账号密码进行表单的提交,SpringSecurity在这过程中又帮助我们做了什么

登录表单的提交的源码分析

在之前了解了为什么所有的请求都会进行认证操作,我们也直接把目光放到源码中这个地方defaultSecurityFilterChain()

@Configuration(
    proxyBeanMethods = false
)
@ConditionalOnWebApplication(
    type = Type.SERVLET
)
class SpringBootWebSecurityConfiguration {
    SpringBootWebSecurityConfiguration() {
    }

    @Configuration(
        proxyBeanMethods = false
    )
    @ConditionalOnMissingBean(
        name = {"springSecurityFilterChain"}
    )
    @ConditionalOnClass({EnableWebSecurity.class})
    @EnableWebSecurity
    static class WebSecurityEnablerConfiguration {
        WebSecurityEnablerConfiguration() {
        }
    }

    @Configuration(
        proxyBeanMethods = false
    )
    @ConditionalOnDefaultWebSecurity
    static class SecurityFilterChainConfiguration {
        SecurityFilterChainConfiguration() {
        }

        @Bean
        @Order(2147483642)
        SecurityFilterChain defaultSecurityFilterChain(HttpSecurity http) throws Exception {
            ((AuthorizeHttpRequestsConfigurer.AuthorizedUrl)http.authorizeHttpRequests().anyRequest()).authenticated();
            //这里就是进行表单登录的入口方法了
            http.formLogin();
            http.httpBasic();
            return (SecurityFilterChain)http.build();
        }
    }
}

我们进入formLogin()中继续看,可以看到这个方法formLogin().这里创建了一个FormLoginConfigurer,我们继续顺着这个构造方法进去看看

	public FormLoginConfigurer<HttpSecurity> formLogin() throws Exception {
		return getOrApply(new FormLoginConfigurer<>());
	}

public FormLoginConfigurer() {
		super(new UsernamePasswordAuthenticationFilter(), null);
		usernameParameter("username");
		passwordParameter("password");
	}

这里可以看到FormLoginConfigurer调用了父类构造并且传了一个UsernamePasswordAuthenticationFilter对象,之前有介绍过这个过滤器是专门做账号密码认证的,那我们继续看向这个过滤器new UsernamePasswordAuthenticationFilter()

    public Authentication attemptAuthentication(HttpServletRequest request, HttpServletResponse response) throws AuthenticationException {
        //首先判断是否为POST请求
        if (this.postOnly && !request.getMethod().equals("POST")) {
            throw new AuthenticationServiceException("Authentication method not supported: " + request.getMethod());
        } else {
            //通过过去用户名和密码进行非空判断
            String username = this.obtainUsername(request);
            username = username != null ? username.trim() : "";
            String password = this.obtainPassword(request);
            password = password != null ? password : "";
            //组装成一个UsernamePasswordAuthenticationToken令牌对象,方便传递
            UsernamePasswordAuthenticationToken authRequest = UsernamePasswordAuthenticationToken.unauthenticated(username, password);
            this.setDetails(request, authRequest);
            //这里将令牌对象传入,继续看看authenticate()做了什么
            return this.getAuthenticationManager().authenticate(authRequest);
        }
    }

最终发现这个authenticate()是一个接口下的抽象方法,实际执行的是 AuthenticationManager 接口实现类 ProviderManager 中的 authenticate() 方法，在该方法中调用 AuthenticationProvider 接口的authenticate() 方法：

我们继续看:

可以发现这里传入了authentication对象最终返回的还是authentication对象,说明这里肯定为这个对象的其他属性进行了操作,我们继续看到provider.authenticate().

实际执行的是 AuthenticationProvider 接口实现类 AbstractUserDetailsAuthenticationProvider 中的 authenticate() 方法，在该方法中调用 retrieveUser() 方法：

	@Override
	public Authentication authenticate(Authentication authentication) throws AuthenticationException {
		Assert.isInstanceOf(UsernamePasswordAuthenticationToken.class, authentication,
				() -> this.messages.getMessage("AbstractUserDetailsAuthenticationProvider.onlySupports",
						"Only UsernamePasswordAuthenticationToken is supported"));
		String username = determineUsername(authentication);
		boolean cacheWasUsed = true;
        //第一次从缓存中获取user对象,肯定是找不到的
		UserDetails user = this.userCache.getUserFromCache(username);
		if (user == null) {
			cacheWasUsed = false;
			try {
                //将输入的用户名和token对象传入retrieveUser()方法,最终返回了UserDetails
				user = retrieveUser(username, (UsernamePasswordAuthenticationToken) authentication);
			}
			catch (UsernameNotFoundException ex) {
				this.logger.debug("Failed to find user '" + username + "'");
				if (!this.hideUserNotFoundExceptions) {
					throw ex;
				}
				throw new BadCredentialsException(this.messages
					.getMessage("AbstractUserDetailsAuthenticationProvider.badCredentials", "Bad credentials"));
			}
			Assert.notNull(user, "retrieveUser returned null - a violation of the interface contract");
		}
		try {
			this.preAuthenticationChecks.check(user);
			additionalAuthenticationChecks(user, (UsernamePasswordAuthenticationToken) authentication);
		}
		catch (AuthenticationException ex) {
			if (!cacheWasUsed) {
				throw ex;
			}
			// 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);
			this.preAuthenticationChecks.check(user);
			additionalAuthenticationChecks(user, (UsernamePasswordAuthenticationToken) authentication);
		}
		this.postAuthenticationChecks.check(user);
		if (!cacheWasUsed) {
			this.userCache.putUserInCache(user);
		}
		Object principalToReturn = user;
		if (this.forcePrincipalAsString) {
			principalToReturn = user.getUsername();
		}
		return createSuccessAuthentication(principalToReturn, authentication, user);
	}

向下查询retrieveUser(),由于retrieveUser()是抽象方法而当前类有且只有一个子类所以直接看到AbstractUserDetailsAuthenticationProvider的子类DaoAuthenticationProvider中实现的retrieveUser()

通过username去加载用户,也是看到这个this.getUserDetailsService().loadUserByUsername().可以看到loadUserByUsername还是一个接口

package org.springframework.security.core.userdetails;

/**
 * Core interface which loads user-specific data.
 * <p>
 * It is used throughout the framework as a user DAO and is the strategy used by the
 * {@link org.springframework.security.authentication.dao.DaoAuthenticationProvider
 * DaoAuthenticationProvider}.
 *
 * <p>
 * The interface requires only one read-only method, which simplifies support for new
 * data-access strategies.
 *
 * @author Ben Alex
 * @see org.springframework.security.authentication.dao.DaoAuthenticationProvider
 * @see UserDetails
 */
public interface UserDetailsService {

	/**
	 * Locates the user based on the username. In the actual implementation, the search
	 * may possibly be case sensitive, or case insensitive depending on how the
	 * implementation instance is configured. In this case, the <code>UserDetails</code>
	 * object that comes back may have a username that is of a different case than what
	 * was actually requested..
	 * @param username the username identifying the user whose data is required.
	 * @return a fully populated user record (never <code>null</code>)
	 * @throws UsernameNotFoundException if the user could not be found or the user has no
	 * GrantedAuthority
	 */
	UserDetails loadUserByUsername(String username) throws UsernameNotFoundException;

}

实际执行的是 UserDetailsService 接口实现类 InMemoryUserDetailsManager 中的 loadUserByUsername() 方法，在该方法中会在 users 集合变量中根据用户输入的帐号获取 UserDetails 信息：

	@Override
	public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
		UserDetails user = this.users.get(username.toLowerCase());
		if (user == null) {
			throw new UsernameNotFoundException(username);
		}
		return new User(user.getUsername(), user.getPassword(), user.isEnabled(), user.isAccountNonExpired(),
				user.isCredentialsNonExpired(), user.isAccountNonLocked(), user.getAuthorities());
	}

类 InMemoryUserDetailsManager 是由内存 map 支持的接口实现类，基于内存存储，不需要后端数据库

最终结论

总结：1. 默认用户名 user 和 控制台的密码，是在 SpringSecurity 提供的 User 类中定义生成的；

        2.在表单认证时，基于 InMemoryUserDetailsManager 类具体进行实现，也就是基于内存的实现。