@GetMapping("/user")
public R<SysUser> getCurrentLoginUser(@AuthenticationPrincipal SysUser user) {
    return R.<SysUser>builder()
            .success(true)
            .msg("获取成功！")
            .data(user)
            .build();
}

我想这样获取当前用户信息，SysUser实现了UserDetails，R是统一的响应对象而已。这样获取当前用户信息需要哪些条件？

我已经实现并配置了UserDetailsService：

@Component
@Primary
public class UserDetailsServiceImpl implements UserDetailsService {

    @Autowired
    private AccountService accountService;

    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
        SysUser loginUser = accountService.findUserByName(username);
        return loginUser;
    }
}

@Configuration
@EnableWebSecurity
//@Order(2)
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Autowired
    private UserDetailsService userDetailsService;

    @Bean
    public PasswordEncoder passwordEncoder() {
        return new BCryptPasswordEncoder();
    }

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
                .userDetailsService(userDetailsService)
                .csrf().disable().headers().frameOptions().disable().and()
                .httpBasic()
                .and()
                .authorizeRequests()
                .anyRequest().authenticated();
    }

    @Override
    protected void configure(AuthenticationManagerBuilder auth) throws Exception {
        auth.userDetailsService(userDetailsService).passwordEncoder(passwordEncoder());
    }

    @Bean
    @Override
    public AuthenticationManager authenticationManagerBean() throws Exception {
        return super.authenticationManagerBean();
    }
}

@Configuration
@EnableResourceServer
public class ResourceServerConfig extends ResourceServerConfigurerAdapter {

    @Autowired
    private UserDetailsService userDetailsService;

    @Override
    public void configure(HttpSecurity http) throws Exception {
        http
                .userDetailsService(userDetailsService)
                .authorizeRequests()
                .antMatchers(HttpMethod.POST, "/account/register").anonymous()
                .antMatchers("/marriage/avatar/**").permitAll()
                .anyRequest().authenticated();
    }

}

为什么@AuthenticationPrincipal注解仍然只能注入String呢？难道还需要哪些条件才能注入UserDetails的实例吗？谢谢老师。