方式一：通过配置文件

spring:
  security:
    user:
      name: root
      password: root

方式二：通过配置类

@Configuration
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(AuthenticationManagerBuilder auth) throws Exception {
        BCryptPasswordEncoder passwordEncoder = new BCryptPasswordEncoder();
        String encode = passwordEncoder.encode("123");
        auth.inMemoryAuthentication().withUser("root").password(encode).roles("admin");
    }

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

方式三：自定义编写实现类

@Configuration
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Autowired
    private UserDetailsService userDetailsService;

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

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

@Service("userDetailsService")
public class MyUserDetailsService implements UserDetailsService {
    @Override
    public UserDetails loadUserByUsername(String s) throws UsernameNotFoundException {
        List<GrantedAuthority> authorityList = AuthorityUtils.commaSeparatedStringToAuthorityList("role");
        return new User("root", new BCryptPasswordEncoder().encode("123"), authorityList);
    }
}