How do methods of storage and authentication confirmation differ when using JWT and server-side sessions?

JWT (JSON Web Token) and server sessions differ in how they store and verify authentication:

• Storage:

  • JWT: The token contains all necessary information (payload) and is signed by the server. The token is stored on the client (usually in localStorage or cookie).
  • Server sessions: The session state is stored on the server (e.g., in memory, database, or cache), and the client only receives a session ID in a cookie.

• Authentication verification:

  • JWT: The client sends the JWT with each request, and the server verifies the signature and extracts data from the token without accessing storage.
  • Server sessions: The server finds session data using the session ID and verifies authentication.

• Features:

  • JWT allows scaling applications without shared session storage, as the state is stored in the token.
  • Server sessions are easier to manage (e.g., sessions can be easily invalidated), but require centralized storage.

Example of using JWT in Java (pseudo-code):

String token = Jwts.builder()
    .setSubject(userId)
    .signWith(secretKey)
    .compact();

// On request
Claims claims = Jwts.parser()
    .setSigningKey(secretKey)
    .parseClaimsJws(token)
    .getBody();
String userId = claims.getSubject();