如何实现Java后端功能开发的安全认证？

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;

import java.util.Date;

public class JwtUtils {
    private static final String SECRET_KEY = "your_secret_key";
    private static final long EXPIRATION_TIME = 86400000; // 24小时

    // 生成JWT令牌
    public static String generateToken(String username, String roles) {
        Date expirationDate = new Date(System.currentTimeMillis() + EXPIRATION_TIME);
        return Jwts.builder()
                .setSubject(username)
                .claim("roles", roles)
                .setExpiration(expirationDate)
                .signWith(SignatureAlgorithm.HS512, SECRET_KEY)
                .compact();
    }

    // 解析JWT令牌
    public static Claims parseToken(String token) {
        return Jwts.parser()
                .setSigningKey(SECRET_KEY)
                .parseClaimsJws(token)
                .getBody();
    }
    
    // 验证JWT令牌是否过期
    public static boolean isTokenExpired(String token) {
        Claims claims = parseToken(token);
        Date expirationDate = claims.getExpiration();
        return expirationDate.before(new Date());
    }
}

@RestController
public class UserController {
    @Autowired
    private UserService userService;

    @PostMapping("/login")
    public String login(@RequestBody Map<String, String> loginInfo) {
        String username = loginInfo.get("username");
        String password = loginInfo.get("password");

        // 验证用户名密码
        boolean isValid = userService.validateLogin(username, password);
        if (!isValid) {
            return "用户名或密码错误";
        }

        // 生成JWT令牌
        String roles = userService.getUserRoles(username);
        String token = JwtUtils.generateToken(username, roles);

        return token;
    }

    @GetMapping("/userinfo")
    public String getUserInfo(@RequestHeader("Authorization") String token) {
        // 验证令牌是否过期
        if (JwtUtils.isTokenExpired(token)) {
            return "令牌已过期";
        }

        // 解析令牌，获取用户名和角色信息
        Claims claims = JwtUtils.parseToken(token);
        String username = claims.getSubject();
        String roles = (String) claims.get("roles");

        // 根据用户名获取用户信息
        UserInfo userInfo = userService.getUserInfoByUsername(username);

        // 返回用户信息和角色信息
        return "用户名：" + userInfo.getUsername() + "，角色：" + roles;
    }
}

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class PasswordUtils {
    public static String encryptPassword(String password) {
        try {
            MessageDigest md = MessageDigest.getInstance("SHA-256");
            byte[] hash = md.digest(password.getBytes(StandardCharsets.UTF_8));
            StringBuilder hexString = new StringBuilder();
            for (byte b : hash) {
                String hex = Integer.toHexString(0xff & b);
                if (hex.length() == 1) {
                    hexString.append('0');
                }
                hexString.append(hex);
            }
            return hexString.toString();
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        }
    }
}