Why JWT matters for APIs in Spring Boot - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the JWT utility class in Spring Boot.

Spring Boot

import org.springframework.security.jwt.[1];

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AJwtUtils

BJwtToken

CJwtHelper

DJwtService

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a class that does not exist in Spring Security JWT package.

The JwtHelper class is used in Spring Security to work with JWT tokens.

2fill in blank

medium

Complete the code to extract the JWT token from the HTTP Authorization header.

Spring Boot

String token = request.getHeader("Authorization").[1]("Bearer ");

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Asubstring

Breplace

Cremove

Dsplit

Attempts:

3 left

💡 Hint

Common Mistakes

Using substring without calculating the correct index.

Using split which returns an array.

We use replace("Bearer ", "") to remove the 'Bearer ' prefix from the header value.

3fill in blank

hard

Fix the error in decoding the JWT token string to get claims.

Spring Boot

Jwt jwt = JwtHelper.[1](token);
String claims = jwt.getClaims();

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Adecode

Bparse

CdecodeToken

Dextract

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'parse' which is not a method in JwtHelper.

Using 'decodeToken' which does not exist.

The correct method to decode a JWT string in Spring Security is decode.

4fill in blank

hard

Fill both blanks to create a JWT token with claims and a secret key.

Spring Boot

String token = JwtHelper.encode([1], new [2]("mySecretKey".getBytes(), "HmacSHA256"));

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Aclaims

BSecretKeySpec

CMac

DKey

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Mac' instead of 'SecretKeySpec' for the key.

Passing the wrong data type for claims.

The encode method takes the claims string and a SecretKeySpec object with the secret key.

5fill in blank

hard

Fill all three blanks to verify a JWT token's signature and extract claims safely.

Spring Boot

try {
  Jwt jwt = JwtHelper.[1](token);
  String claims = jwt.getClaims();
  // Verify signature
  SignatureVerifier verifier = new [2]("mySecretKey");
  jwt.[3](verifier);
} catch (Exception e) {
  // Handle invalid token
}

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Adecode

BMacSigner

CverifySignature

DJwtVerifier

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong method names for decoding or verification.

Using a wrong class for the signer.

We decode the token, create a MacSigner with the secret key, then call verifySignature to check the token's validity.