code: protected void copyResponseEntity(HttpResponse proxyResponse, HttpServletResponse servletResponse)
              throws IOException
     {
        HttpEntity entity = proxyResponse.getEntity();
        if (entity != null)
        {
           OutputStream servletOutputStream = servletResponse.getOutputStream();
           try
           {
              entity.writeTo(servletOutputStream);
           }
           finally
           {
              closeQuietly(servletOutputStream);
           }
        }
     }
docs: Copy response body data (the entity) from the proxy to the servlet client.