From c9f2a8390a27f6dd78153026db03d913c9175f0f Mon Sep 17 00:00:00 2001
From: Art <d.art.shishkin@gmail.com>
Date: Sat, 4 Sep 2021 17:32:27 +0300
Subject: [PATCH] 27. JWT Token Provider - Part 2 (#2)

---
 .../backend/utility/JwtTokenProvider.java     | 38 ++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/support-portal-backend/src/main/java/net/shyshkin/study/fullstack/supportportal/backend/utility/JwtTokenProvider.java b/support-portal-backend/src/main/java/net/shyshkin/study/fullstack/supportportal/backend/utility/JwtTokenProvider.java
index 11bf83e..d587c7a 100644
--- a/support-portal-backend/src/main/java/net/shyshkin/study/fullstack/supportportal/backend/utility/JwtTokenProvider.java
+++ b/support-portal-backend/src/main/java/net/shyshkin/study/fullstack/supportportal/backend/utility/JwtTokenProvider.java
@@ -1,11 +1,18 @@
 package net.shyshkin.study.fullstack.supportportal.backend.utility;
 
 import com.auth0.jwt.JWT;
+import com.auth0.jwt.JWTVerifier;
 import com.auth0.jwt.algorithms.Algorithm;
+import com.auth0.jwt.exceptions.JWTVerificationException;
 import net.shyshkin.study.fullstack.supportportal.backend.domain.UserPrincipal;
 import org.springframework.beans.factory.annotation.Value;
+import org.springframework.security.core.GrantedAuthority;
+import org.springframework.security.core.authority.SimpleGrantedAuthority;
 
+import java.util.Arrays;
 import java.util.Date;
+import java.util.List;
+import java.util.stream.Collectors;
 
 import static net.shyshkin.study.fullstack.supportportal.backend.constant.SecurityConstants.*;
 
@@ -26,7 +33,36 @@ public class JwtTokenProvider {
                 .sign(Algorithm.HMAC512(secret));
     }
 
+    public List<GrantedAuthority> getAuthorities(String token) {
+        String[] claims = getClaimsFromToken(token);
+        return Arrays.stream(claims)
+                .map(SimpleGrantedAuthority::new)
+                .collect(Collectors.toList());
+    }
+
+    private String[] getClaimsFromToken(String token) {
+        JWTVerifier verifier = getJwtVerifier();
+        try {
+            return verifier.verify(token)
+                    .getClaim(AUTHORITIES)
+                    .asArray(String.class);
+        } catch (JWTVerificationException exception) {
+            throw new JWTVerificationException(ACCESS_DENIED_MESSAGE);
+        }
+    }
+
+    private JWTVerifier getJwtVerifier() {
+
+        Algorithm algorithm = Algorithm.HMAC256(secret);
+        return JWT.require(algorithm)
+                .withIssuer(GET_ARRAYS_LLC)
+                .build(); //Reusable verifier instance
+    }
+
     private String[] getClaimsFromUser(UserPrincipal userPrincipal) {
-        return new String[0];
+        return userPrincipal.getAuthorities()
+                .stream()
+                .map(GrantedAuthority::getAuthority)
+                .toArray(String[]::new);
     }
 }