java写一个token

下面是一个简单的 Java 实现 JWT Token 的示例：

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;
import java.util.Date;

public class JwtTokenGenerator {
    
    private static final String SECRET_KEY = "my_secret_key"; // 加密秘钥
    private static final long EXPIRATION_TIME = 86400000L; // token 过期时间，这里设置为 24 小时

    public static String generateToken(String username) {
        Date now = new Date();
        Date expiration = new Date(now.getTime() + EXPIRATION_TIME);

        return Jwts.builder()
                .setSubject(username)
                .setIssuedAt(now)
                .setExpiration(expiration)
                .signWith(SignatureAlgorithm.HS512, SECRET_KEY)
                .compact();
    }

    public static boolean validateToken(String token) {
        try {
            Jwts.parser().setSigningKey(SECRET_KEY).parseClaimsJws(token);
            return true;
        } catch (Exception ex) {
            return false;
        }
    }

    public static String getUsernameFromToken(String token) {
        Claims claims = Jwts.parser().setSigningKey(SECRET_KEY).parseClaimsJws(token).getBody();
        return claims.getSubject();
    }
}

使用示例：

public class JwtTokenGeneratorTest {
    
    public static void main(String[] args) {
        String token = JwtTokenGenerator.generateToken("test_user");
        System.out.println(token);
        
        boolean isValid = JwtTokenGenerator.validateToken(token);
        System.out.println(isValid);
        
        String username = JwtTokenGenerator.getUsernameFromToken(token);
        System.out.println(username);
    }
}