How to update metadata using Amazon S3 SDK

I've just found that copying to object to itself actually does change the headers properly. I was copying it to a second file for testing purposes to avoid overwriting the original.

But for some strange reason copying to a different file doesn't change the headers, but copying to the same file does.

In Java, You can copy object to the same location. Here metadata will not copy while copying an Object. You have to get metadata of original and set to copy request. This method is more recommended to insert or update metadata of an Amazon S3 object

ObjectMetadata metadata = amazonS3Client.getObjectMetadata(bucketName, fileKey);
ObjectMetadata metadataCopy = new ObjectMetadata();
metadataCopy.addUserMetadata("yourKey", "updateValue");
metadataCopy.addUserMetadata("otherKey", "newValue");
metadataCopy.addUserMetadata("existingKey", metadata.getUserMetaDataOf("existingValue"));

CopyObjectRequest request = new CopyObjectRequest(bucketName, fileKey, bucketName, fileKey)
      .withSourceBucketName(bucketName)
      .withSourceKey(fileKey)
      .withNewObjectMetadata(metadataCopy);

amazonS3Client.copyObject(request);