@Value not picking from application.properties

Question

Have following JWTTokenService class:

package com.project.blogapi.security;

import com.auth0.jwt.JWT;
import com.auth0.jwt.algorithms.Algorithm;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;

import java.time.Instant;
import java.util.Date;

import static java.lang.System.*;

@Service
public class JWTTokenService implements TokenService {

    private final Algorithm algorithm;
    private final String SIGNING_KEY;
    private final long TOKEN_EXPIRY_MILLIS = (1000 * 60 * 60 * 24);
    private final String ISSUER = "blog-api";
    public JWTTokenService(String signingKey) {
        SIGNING_KEY = signingKey;
        this.algorithm = Algorithm.HMAC256(SIGNING_KEY);
    }

    @Override
    public String createAuthToken(String username) {
        String token = JWT.create()
                .withIssuer(ISSUER)
                .withIssuedAt(new java.util.Date())
                .withExpiresAt(new java.util.Date(System.currentTimeMillis() + TOKEN_EXPIRY_MILLIS))
                .withSubject(username)
                .sign(algorithm);
        return token;
    }

    @Override
    public String getUsernameFromToken(String token) throws IllegalStateException {
        var verifier = JWT.require(algorithm)
                .withIssuer(ISSUER)
                .build();

        var decodedToken = verifier.verify(token);
        return decodedToken.getSubject();
    }
}

have a TokeService Interface:

package com.project.blogapi.security;

public interface TokenService {
    /*
        create a JWT or Service side token for given username
     */
    String createAuthToken(String username);
    String getUsernameFromToken(String token) throws IllegalStateException;

}

and a JWTTokenProperties to create JWTTokenService with value ideally coming from application.properties

package com.project.blogapi.security;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class JWTTokenProperties {

    public static @Value("${key}") String SIGNING_KEY;

    public static JWTTokenService create(){
        return new JWTTokenService(SIGNING_KEY);
    }
}

have tried different ways but SIGNING_KEY is always null

tried without tokenproperties directly wiht jwttokenservices. did not work.

Answer 1

Remove static modifier like so:

public @Value("${key}") String SIGNING_KEY;

Answer 2

As mentioned by @DingHao you should remove the static keyword from your property field, but now the problem would be that your static method will try to access an instance property which is compilation error. Try also to remove the static keyword from your method.

And if this isn't an option for you, you should check this explanation for how to work around setting a static property using setter dependency injection: https://www.baeldung.com/spring-inject-static-field

As a side note, I would recommend naming your properties keys differently: spring.myapp.key instead of just key, because Spring has an order in which is searching for properties values (System properties, Environment properties, and lastly your properties file from your codebase) and could find key somewhere else and put that value instead of yours leading to unwanted behaviour.