Error log improvements & handle jwksinfo null instance

components/apimgt/org.wso2.carbon.apimgt.impl/src/main/java/org/wso2/carbon/apimgt/impl/jwt/JWTValidatorImpl.java

@@ -167,9 +167,18 @@
                 }
             }
             return JWTUtil.verifyTokenSignature(signedJWT, certificateAlias);
-        } catch (ParseException | JOSEException | IOException e) {
-            log.error("Error while parsing JWT", e);
+        } catch (ParseException e) {
+            log.error("Error while parsing JWKS information", e);
             throw new APIManagementException("Error while parsing JWT", e);
+        } catch (JOSEException e) {
+            log.error("Error while verifying token signature", e);
+            throw new APIManagementException("Error while parsing JWT", e);
+        } catch (IOException e) {
+            log.error("Error while connecting to JWKS endpoint", e);
+            throw new APIManagementException("Error while parsing JWT", e);
+        } catch (APIManagementException e) {
+            log.error("Error while retrieving JWKS information", e);
+            throw new APIManagementException(e.getMessage(), e);
         }
 
     }
@@ -220,11 +229,15 @@
         jwtValidationInfo.setJti(jwtClaimsSet.getJWTID());
     }
 
-    private JWKSet retrieveJWKSet() throws IOException, ParseException {
+    private JWKSet retrieveJWKSet() throws IOException, ParseException, APIManagementException {
 
         String jwksInfo = JWTUtil
                 .retrieveJWKSConfiguration(tokenIssuer.getJwksConfigurationDTO().getUrl());
-        jwkSet = JWKSet.parse(jwksInfo);
+        if (jwksInfo != null) {
+            jwkSet = JWKSet.parse(jwksInfo);
+        } else {
+            throw new APIManagementException("Invalid JWKS endpoint.");
+        }
         return jwkSet;
     }
 }