案例（写死的用户密码）
package com.zking.security.service;import org.springframework.security.core.GrantedAuthority;
import org.springframework.security.core.authority.AuthorityUtils;
import org.springframework.security.core.userdetails.User;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.core.userdetails.UsernameNotFoundException;
import org.springframework.stereotype.Service;import java.util.List;/*** 登录服务类，实现Spring Security的UserDetailsService接口*/
@Service
public class LoginService implements UserDetailsService {/*** 根据用户名加载用户信息** @param username 用户名* @return UserDetails对象，包含用户信息* @throws UsernameNotFoundException 如果用户不存在，则抛出此异常*/@Overridepublic UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {// 检查用户名是否匹配预设值，如果不匹配则抛出异常if (!"jack".equals(username)){throw new UsernameNotFoundException("用户名不存在");}// 预设的用户密码String pwd = "$2a$10$k8GypMMYDjEr804BC.jR0O.ZSxWn082oWgvuilomBiN31ajb43XVO";// 用户角色及权限//检查用户名是否为 jack：检查传入的用户名是否为 "jack"。//如果不是 "jack"，则抛出 UsernameNotFoundException 异常。//如果是 "jack"，则继续执行。//一个用户拥有一个或多个角色，每个角色可能拥有多个权限。List<GrantedAuthority> authorities=AuthorityUtils.commaSeparatedStringToAuthorityList("sys:prod:list,ROLE_jack
