[R9] Get jwt subject use case

src/main/java/com/mirna/hospitalmanagementapi/application/usecase/auth/jwt/GetJWTSubjectUseCase.java

@@ -0,0 +1,38 @@
+package com.mirna.hospitalmanagementapi.application.usecase.auth.jwt;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Component;
+
+import com.auth0.jwt.JWT;
+import com.auth0.jwt.JWTVerifier;
+import com.auth0.jwt.algorithms.Algorithm;
+import com.auth0.jwt.interfaces.DecodedJWT;
+
+/**
+ * This class is used to execute the JWT verify method using Algorithm HMAC256 and application secret
+ * 
+ * @author Mirna Gama
+ * @version 1.0
+ */
+@Component
+public class GetJWTSubjectUseCase {
+
+	@Value("${api.security.token.secret}")
+    private String secret;
+	
+	/**
+	 * Gets the jwt subject 
+	 * 
+	 * @param token The json web token on request header
+	 * @return A string containing the subject from the decoded jwt
+	 */
+	public String execute(String token) {
+		Algorithm algorithm = Algorithm.HMAC256(secret);
+	    DecodedJWT decodedJWT = JWT.require(algorithm)
+	    	.withIssuer("Hospital-Management-API")
+	    	.build()
+	        .verify(token);
+	        
+	    return decodedJWT.getSubject();
+	}
+}