JWT.java

package com.example.accessingdatamysql.auth;

import javax.crypto.spec.SecretKeySpec;
import javax.xml.bind.DatatypeConverter;
import java.security.Key;

import io.jsonwebtoken.*;

import java.util.Date;
import org.springframework.stereotype.Component;

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

/*
    A simple static class that is used to create and decode JWTs.
 */
public class JWT{

    
    // The secret key. This should be in a property file NOT under source
    // control and not hard coded in real life. We're putting it here for
    // simplicity.
    private static String SECRET_KEY = "secret dev key";
    private static final long DEFAULT_TTL = 99999;

    //Sample method to construct a JWT
    public static String createJWT(String id, String issuer, String subject, long ttlMillis) {

        //The JWT signature algorithm we will be using to sign the token
        SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.HS256;

        long nowMillis = System.currentTimeMillis();
        Date now = new Date(nowMillis);

        //We will sign our JWT with our ApiKey secret
        byte[] apiKeySecretBytes = DatatypeConverter.parseBase64Binary(SECRET_KEY);
        Key signingKey = new SecretKeySpec(apiKeySecretBytes, signatureAlgorithm.getJcaName());

        //Let's set the JWT Claims
        JwtBuilder builder = Jwts.builder().setId(id)
                .setIssuedAt(now)
                .setSubject(subject)
                .setIssuer(issuer)
                .signWith(signatureAlgorithm, signingKey);

        //if it has been specified, let's add the expiration
        if (ttlMillis >= 0) {
            long expMillis = nowMillis + ttlMillis + DEFAULT_TTL; // pad with default amount 
            Date exp = new Date(expMillis);
            builder.setExpiration(exp);
        }

        //Builds the JWT and serializes it to a compact, URL-safe string
        return builder.compact();
    }

    public static Claims decodeJWT(String jwt) {

        //This line will throw an exception if it is not a signed JWS (as expected)
        try 
        {
            Claims claims = Jwts.parser()
                    .setSigningKey(DatatypeConverter.parseBase64Binary(SECRET_KEY))
                    .parseClaimsJws(jwt).getBody();
            return claims;
        }
        catch (Exception e)
        {
            return null;
        }
   }

}