service层代码：

    public String login(String username, String password, String code, String uuid)
        ...// 用户验证
        Authentication authentication = null;
            // 该方法会去调用UserDetailsServiceImpl.loadUserByUsername
            authentication = authenticationManager
                    .authenticate(new UsernamePasswordAuthenticationToken(username, password));
      ...// 生成token
        return tokenService.createToken(loginUser);
其中authenticationManager是在SecurityConfig中注入的，如下：
 @Bean
    @Override
    public AuthenticationManager authenticationManagerBean() throws Exception
        return super.authenticationManagerBean();
SecurityConfig的完整代码如下：
package com.ruoyi.framework.config;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.http.HttpMethod;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
import org.springframework.security.config.annotation.method.configuration.EnableGlobalMethodSecurity;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
import org.springframework.security.config.http.SessionCreationPolicy;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter;
import com.ruoyi.framework.security.filter.JwtAuthenticationTokenFilter;
import com.ruoyi.framework.security.handle.AuthenticationEntryPointImpl;
import com.ruoyi.framework.security.handle.LogoutSuccessHandlerImpl;
 * spring security配置
 * @author ruoyi
@EnableGlobalMethodSecurity(prePostEnabled = true, securedEnabled = true)
public class SecurityConfig extends WebSecurityConfigurerAdapter
     * 自定义用户认证逻辑
    @Autowired
    private UserDetailsService userDetailsService;
     * 认证失败处理类
    @Autowired
    private AuthenticationEntryPointImpl unauthorizedHandler;
     * 退出处理类
    @Autowired
    private LogoutSuccessHandlerImpl logoutSuccessHandler;
     * token认证过滤器
    @Autowired
    private JwtAuthenticationTokenFilter authenticationTokenFilter;
     * 解决 无法直接注入 AuthenticationManager
     * @return
     * @throws Exception
    @Bean
    @Override
    public AuthenticationManager authenticationManagerBean() throws Exception
        return super.authenticationManagerBean();
     * anyRequest          |   匹配所有请求路径
     * access              |   SpringEl表达式结果为true时可以访问
     * anonymous           |   匿名可以访问
     * denyAll             |   用户不能访问
     * fullyAuthenticated  |   用户完全认证可以访问（非remember-me下自动登录）
     * hasAnyAuthority     |   如果有参数，参数表示权限，则其中任何一个权限可以访问
     * hasAnyRole          |   如果有参数，参数表示角色，则其中任何一个角色可以访问
     * hasAuthority        |   如果有参数，参数表示权限，则其权限可以访问
     * hasIpAddress        |   如果有参数，参数表示IP地址，如果用户IP和参数匹配，则可以访问
     * hasRole             |   如果有参数，参数表示角色，则其角色可以访问
     * permitAll           |   用户可以任意访问
     * rememberMe          |   允许通过remember-me登录的用户访问
     * authenticated       |   用户登录后可访问
    @Override
    protected void configure(HttpSecurity httpSecurity) throws Exception
        httpSecurity
                // CRSF禁用，因为不使用session
                .csrf().disable()
                // 认证失败处理类
                .exceptionHandling().authenticationEntryPoint(unauthorizedHandler).and()
                // 基于token，所以不需要session
                .sessionManagement().sessionCreationPolicy(SessionCreationPolicy.STATELESS).and()
                // 过滤请求
                .authorizeRequests()
                // 对于登录login 验证码captchaImage 允许匿名访问
                .antMatchers("/login", "/captchaImage").anonymous()
                .antMatchers(
                        HttpMethod.GET,
                        "/*.html",
                        "/**/*.html",
                        "/**/*.css",
                        "/**/*.js"
                ).permitAll()
                .antMatchers("/profile/**").anonymous()
                .antMatchers("/common/download**").anonymous()
                .antMatchers("/common/download/resource**").anonymous()
                .antMatchers("/swagger-ui.html").anonymous()
                .antMatchers("/swagger-resources/**").anonymous()
                .antMatchers("/webjars/**").anonymous()
                .antMatchers("/*/api-docs").anonymous()
                .antMatchers("/druid/**").anonymous()
                // 除上面外的所有请求全部需要鉴权认证
                .anyRequest().authenticated()
                .and()
                .headers().frameOptions().disable();
        httpSecurity.logout().logoutUrl("/logout").logoutSuccessHandler(logoutSuccessHandler);
        // 添加JWT filter
        httpSecurity.addFilterBefore(authenticationTokenFilter, UsernamePasswordAuthenticationFilter.class);
     * 强散列哈希加密实现
    @Bean
    public BCryptPasswordEncoder bCryptPasswordEncoder()
        return new BCryptPasswordEncoder();
     * 身份认证接口
    @Override
    protected void configure(AuthenticationManagerBuilder auth) throws Exception
        auth.userDetailsService(userDetailsService).passwordEncoder(bCryptPasswordEncoder());
SecurityConfig
最终经过一系列处理，到数据库的用户认证要走到如下逻辑：
@Service
public class UserDetailsServiceImpl implements UserDetailsService
    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException
        SysUser user = userService.selectUserByUserName(username);
        if (StringUtils.isNull(user))
            log.info("登录用户：{} 不存在.", username);
            throw new UsernameNotFoundException("登录用户：" + username + " 不存在");
        else if (UserStatus.DELETED.getCode().equals(user.getDelFlag()))
            log.info("登录用户：{} 已被删除.", username);
            throw new BaseException("对不起，您的账号：" + username + " 已被删除");
        else if (UserStatus.DISABLE.getCode().equals(user.getStatus()))
            log.info("登录用户：{} 已被停用.", username);
            throw new BaseException("对不起，您的账号：" + username + " 已停用");
        return createLoginUser(user);
而UserDetailsServiceImpl在SecurityConfig中是这样配置进去的：
     * 身份认证接口
    @Override
    protected void configure(AuthenticationManagerBuilder auth) throws Exception
        auth.userDetailsService(userDetailsService).passwordEncoder(bCryptPasswordEncoder());
那看完上边这个应用流程后，还有两个疑问：
1、是如何调用到UserDetailsServiceImpl里的loadUserByUsername；
2、loadUserByUsername方法中只校验了用户名是否存在，并没有校验密码是否正确，密码的校验又在哪里呢。
二、执行流程
下面来看下这两个问题：
经过代码断点跟踪，代码会走到如下地方（当然前边还有一些代码逻辑，本次仅从上述2个问题去重点跟部分代码）:
AbstractUserDetailsAuthenticationProvider类的authenticate方法：
public Authentication authenticate(Authentication authentication)
            throws AuthenticationException {
       ...try {
　　　　　　　　　　//此方法会去获取用户信息，会一步步调用到UserDetailsServiceImpl里的loadUserByUsername方法
                user = retrieveUser(username,
                        (UsernamePasswordAuthenticationToken) authentication);
           try {
            preAuthenticationChecks.check(user);
　　　　　　　　//此方法中会去校验用户的密码
            additionalAuthenticationChecks(user,
                    (UsernamePasswordAuthenticationToken) authentication);
       ...return createSuccessAuthentication(principalToReturn, authentication, user);
retrieveUser方法实际调用的地方，DaoAuthenticationProvider类中：
protected final UserDetails retrieveUser(String username,
            UsernamePasswordAuthenticationToken authentication)
            throws AuthenticationException {
       　　...
//调用我们自定义的UserDetailsServiceImpl进行校验
UserDetails loadedUser = this.getUserDetailsService().loadUserByUsername(username); 
... 
}
additionalAuthenticationChecks方法实际调用的地方，DaoAuthenticationProvider类中：
protected void additionalAuthenticationChecks(UserDetails userDetails,
            UsernamePasswordAuthenticationToken authentication)
            throws AuthenticationException {
        if (authentication.getCredentials() == null) {
            logger.debug("Authentication failed: no credentials provided");
            throw new BadCredentialsException(messages.getMessage(
                    "AbstractUserDetailsAuthenticationProvider.badCredentials",
                    "Bad credentials"));
        String presentedPassword = authentication.getCredentials().toString();
　　　　　　//进行密码的校验
        if (!passwordEncoder.matches(presentedPassword, userDetails.getPassword())) {
            logger.debug("Authentication failed: password does not match stored value");
            throw new BadCredentialsException(messages.getMessage(
                    "AbstractUserDetailsAuthenticationProvider.badCredentials",
                    "Bad credentials"));
以上就是Spring Security认证的简单流程，采用默认的AbstractUserDetailsAuthenticationProvider和DaoAuthenticationProvider（都是AuthenticationProvider接口的实现类）来实现。
另外：我们也可以自定义类实现AuthenticationProvider接口来完全自定义用户的认证过程。