code: public SourceBody getSource(Unit unit, UnitRequest msg) {
          SourceBody body = new SourceBody();
          body.setSource(msg.getContext().getUri());
          if (body.getSource() == null || body.getSource().trim().length() <= 0) {
              body.setSource(EnvUtil.getApplication());
          }
          return body;
      }
docs: 获取请求来源