<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt</artifactId>
    <version>0.9.1</version>
</dependency>
工具类:
import com.example.online_class.domain.User;
import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;
import java.util.Date;
/**
 * JWT工具类
 */
public class JwtUtils {
    /**
     * 有效时间
     */
    private static final long EXPIRE = 60000 * 60 * 24 * 7;
    /**
     * 加密密钥
     */
    private static final String SECRET = "xxx";
    /**
     * 令牌前缀
     */
    private static final String TOKEN_PREFIX = "xxx";
    /**
     * subject
     */
    private static final String SUBJECT = "xxx";
    /**
     * 根据用户信息,生成令牌
     * @param user
     * @return
     */
    public static String geneJsonWebToken(User user){
        String token = Jwts.builder().setSubject(SUBJECT)
                .claim("name",user.getName())
                .claim("id",user.getId())
                .claim("head_img",user.getHeadImg())
                .setIssuedAt(new Date())
                .setExpiration(new Date(System.currentTimeMillis() + EXPIRE))
                .signWith(SignatureAlgorithm.ES256,SECRET)
                .compact();
        token = TOKEN_PREFIX + token;
        return token;
    }
    /**
     * 校验token的方法
     */
    public static Claims checkJWT(String token){
        try {
            Claims claims = Jwts.parser().setSigningKey(SECRET)
                    .parseClaimsJws(token.replace(TOKEN_PREFIX,""))
                    .getBody();
            return claims;
        }catch (Exception e){
            return null;
        }
    }
}