Body JSON / UTF-8 encoding

I build a agent code to act as web service, the problem is the response body content.

The HTTP GET request to my web service and define the body content should be
a. body is properly JSON-encoded
b. body uses UTF-8 content encoding

I passed the JSON format but failed at UTF-8 encode.
Please advice how to use UTF-8 encode? Thanks!

Here is the body code of response:

response.header(“Accept”, “application/json”);
response.header(“Accept-Charset”, “utf-8”);
response.header(“Accept-Encoding”, “gzip, deflate”);
response.header(“Content-Type”, “application/json”);

                local body="";
                body = 
                        "accessToken": "taSvYgeXfM1HjVISJbUXVBIw1YUkKABm",
                        "samples": {}
                response.send(200, http.jsonencode(body));