code: public void putCampaign(String campaign) throws JSONException {
          if (campaign != null) {
              this.campaign = campaign;
              this.put(Defines.LinkParam.Campaign.getKey(), campaign);
          }
      }
docs: <b>A string value that represents the campaign associated with this link.</b>
  
  @param campaign A {@link String} value specifying the campaign.
  @throws JSONException The parameter value must be in valid JSON format, or a
  {@link JSONException} will be thrown.