How to set headers of a JSON/XML response in 'format.json/xml { render :json/xml => @user.to_json/xml }'?

I am using Ruby on Rails 3 and I am trying to set va开发者_Python百科lues of a JSON/XML response.

In my controller I have

respond_to do |format|
  format.xml { render :xml => @user.to_xml }
  format.json { render :json => @user.to_json }
end

When I make a HTTP GET request for JSON/XML, it is set common values like these

header: 
  date: 
  - Fri, 18 Feb 2011 18:02:55 GMT
  server: 
  - Apache ...
  etag: 
  - "\"0dbfd0ec23934921144bd57d383db443\""
  cache-control: 
  - max-age=0, private, must-revalidate
  x-ua-compatible: 
  - IE=Edge
  x-runtime: 
  - "0.033209"
  status: 
  - "200"
  transfer-encoding: 
  - chunked
  content-type: 
  - application/json; charset=utf-8 #or application/xml; charset=utf-8
http_version: "1.1"
message: OK
read: true

I would like to add/set header values and add new parameters like message2 or header2.

How can I do that in format.json/xml { render :json/xml => @user.to_json/xml } syntax?

The format.foo { render ... } thing takes a block. You can put whatever you want there:

format.json do
  response['X-Message-1'] = 'Hello'
  render :json => @user.to_json
end