Solved: Refactoring java code

HI,
I have the following code in my spring mvc controller i want to refactor it .

 private String getBase64EncodedIframeSrc(String body) {
        String contentCss = "<link href=\"https://cdn.ckeditor.com/4.5.6/full/contents.css\" rel=\"stylesheet\" type=\"text/css\"/>";
        String htmlBody = "<body><div id=\"textArea\" class=\"cke_editable cke_editable_themed cke_contents_ltr cke_show_borders\">" + body + "</div><body>";
        String iframeSrc = contentCss + htmlBody;
        String base64encodedString= null;
        try {
            base64encodedString = Base64.getEncoder().encodeToString(iframeSrc.getBytes("utf-8"));
        } catch (UnsupportedEncodingException e) {
            logger.error("Exception while encoding iframe source in base64",e.getMessage());
        }
        return base64encodedString;
    }

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Please help me write it in a better way.
Things that i want to avoid :
1) I have manually put \" at many places in both the strings contentCss and htmlBody
2) Handling of exception. Is it possible to move it out of controller?

I am extending my controller with a basecontroller where i am handling other exceptions like :

 @ExceptionHandler(EmptyResultDataAccessException.class)
    public ResponseEntity<String> handleServerException(EmptyResultDataAccessException e) {
        String message = "Page not found";
        logger.error(message, e);
        return new ResponseEntity<String>(message, HttpStatus.NOT_FOUND);
    }

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But this approach will not work here...
Any other possible suggestions for refactoring and making it better ?

Thanks