- jwt decoding without a key

json-web-token/build.gradle.kts

@@ -17,6 +17,6 @@ dependencies {
     runtimeOnly("io.jsonwebtoken:jjwt-impl:0.12.5")
     runtimeOnly("io.jsonwebtoken:jjwt-jackson:0.12.5")
 
-    // another library
+    // another library, good for a client side
     implementation("com.auth0:java-jwt:4.4.0")
 }

json-web-token/src/main/java/kr/pe/elex/examples/Jwt0Sample.java

@@ -25,12 +25,15 @@ public class Jwt0Sample {
 				.withSubject("Hello")
 				.sign(Algorithm.HMAC256(key));
 	}
-	public static DecodedJWT parseToken(String token){
+	public static DecodedJWT parseToken(String token, byte[] key){
 		return JWT.require(Algorithm.HMAC256(key))
 				.withIssuer("Elex")
 				.build()
 				.verify(token);
 	}
+	public static DecodedJWT parseToken(String token){
+		return JWT.decode(token);
+	}
 
 	public static void main(String... args){
 		String token = genToken();

json-web-token/src/main/java/kr/pe/elex/examples/JwtsSample.java

@@ -76,6 +76,25 @@ public class JwtsSample {
 			throw e;
 		}
 	}
+	public static String decodeToken(final String token) throws JwtException {
+		String[] chunks = token.split("\\.");
+		Base64.Decoder decoder = Base64.getUrlDecoder();
+
+		String header = new String(decoder.decode(chunks[0]));
+		String payload = new String(decoder.decode(chunks[1]));
+
+		return payload;
+
+
+	}
+	public static String decodeToken2(final String token) throws JwtException {
+		String s = Jwts.parser().unsecured().build().parseSignedClaims(token)
+				.getPayload().getSubject();
+
+		return s;
+
+
+	}
 
 	public static String parseToken(final String token, final PublicKey key) throws JwtException {
 		try {

json-web-token/src/test/java/kr/pe/elex/examples/SampleTest.java

@@ -26,7 +26,25 @@ import java.util.Random;
 import static org.junit.jupiter.api.Assertions.*;
 
 class SampleTest {
+@Test
+void test2(){
+	final SecretKey signingKey = Jwts.SIG.HS384.key().build();
+	String token = Jwts.builder()
+			.header().type("JWT")
+			.and()
+			.issuer("Elex")
+			.expiration(Date.from(Instant.now().plus(3, ChronoUnit.HOURS)))
+			.claim("userId", 3)
+			.subject("hello")
+			.signWith(signingKey)
+			.compact();
+	String payload = JwtsSample.decodeToken(token);
 
+	System.out.println(payload);
+
+	//String sub = JwtsSample.decodeToken2(token);
+	//System.out.println(sub);
+}
 	@Test
 	void test() throws NoSuchAlgorithmException, InvalidKeySpecException {
 		byte[] key = new byte[32];