Top JWT(JSON Web Token) frequently asked interview questions.

In this post we will look at JWT(JSON Web Token) Interview questions. Examples are provided with explanations.

Q: What is need for JWT?

A :

• JWT stands for JSON Web Token
• It is pronounced as JAWT
• It is Open Standard - RFC7519
• JWT makes it possible to communicate securely between two bodies
• JWT is used for Authorization

Understanding the need for JSON Web Token(JWT)

Q: What are the advantages of JWT?

A :

Advantages of JWT Authorization

• JWT is self contained. It is a value token. So during each validation the Gmail server does not needs to fetch the information corresponding to it.
• It is digitally signed so if any one modifies it the server will know about it
• It is most suitable for Microservices Architecture
• It has other advantages like specifying the expiration time.

Q: What is the structure of JWT?

A : A JWT consists of 3 parts -

• Header
• Payload
• Signature

Q: What is expiration date of JWT?

A : Expiration Time - This the time for which we want the generated JWT to be valid for. This will be in milliseconds. Suppose we want the JWT to be valid for 5 hours, then we will specify this value as 18000000

Q: How do we specify expiration date of JWT?

A :

	private String doGenerateToken(Map<String, Object> claims, String subject) {

		return Jwts.builder().setClaims(claims).setSubject(subject).setIssuedAt(new Date(System.currentTimeMillis()))
				.setExpiration(new Date(System.currentTimeMillis() + jwtExpirationInMs)).signWith(SignatureAlgorithm.HS512, secret).compact();
	}

See Also
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