The request body is an IO input stream. If the RAW_POST_DATA environment
variable is already set, wrap it in a StringIO.
# File actionpack/lib/action_dispatch/http/request.rb, line 349
def body
if raw_post = get_header("RAW_POST_DATA")
raw_post = (+raw_post).force_encoding(Encoding::BINARY)
StringIO.new(raw_post)
else
body_stream
end
end