A public URL is generated for a google CDN object, if bucket object is not public, authentication issue occurs.

[shivamkrpandey]

Added makePublic: true in the config to get the permanent URL of the bucket object but the object was not set to be publically readable in the bucket hence URL is generated but the authorisation issues occur for all the generated mediaLink.

[shivamkrpandey]

Here on docs I found a solution

BlobId blobId = BlobId.of(bucketName, blobName, blobGeneration);
Acl acl = storage.createAcl(blobId, Acl.of(User.ofAllUsers(), Role.READER));

#Ref: https://github.com/GoogleCloudPlatform/google-cloud-java/blob/master/google-cloud-examples/src/main/java/com/google/cloud/examples/storage/snippets/StorageSnippets.java

We need to create an acl entry (change in the Access control list) for the bucket object that is blobId here to make individual objects publicly readable.