title: where can I set up character encoding in WSO2 EI
body: <p>I'm new to WSO2,<br>
  In the WSO2 ESB profile, I tried to send a message like this:<br>
  <code>{"name":"中国"}</code><br>
  but after proxy service and in my back-end service it printed:<br>
  <code>{"name":"???"}</code></p>
  
  <p>it also appeared both in API, when I debug the api, I can see the payload as already unreadable.
  So I think I must set up character encoding before the payload coming in. But where can I do this?  </p>
  
  <p>Can you help me?</p>